THE UNIVERSITY OF WESTERN
AUSTRALIA
SCHOOL OF ANIMAL BIOLOGY
Photo: Danny Tang
ANIM2203
INVERTEBRATE ZOOLOGY
SEMESTER 1, 2011
THE UNIVERSITY OF WESTERN AUSTRALIA
ACKNOWLEDGES THAT ITS CAMPUS
IS SITUATED ON NOONGAR LAND
so that the Noongar people remain the spiritual and cultural custodians of their land, and continue to
practice their values, languages, beliefs and knowledge
PRODROMOS
Invertebrate Zoology, ANIM2203, introduces the wide range of invertebrates in such
a way that students should:
¾ Be able to recognize, on sight, representatives of the major phyla;
¾ Understand the phyletic relationships between the common forms; and
¾ Know what literature to turn to help in your later professional life.
In this auspicious year of the 200th anniversary of the birth of Charles Darwin, and
perhaps equally auspicious year of the 150th anniversary of the ‘birth’ of “The Origin of
Species…”, it is worthwhile to reflect on the relevance of the ‘Theory of Evolution’ for
ANIM2203. Evolutionary thinking is the major intellectual thread underpinning modern
biology so that no longer is it necessary to learn the characteristics defining each
phylum. Instead, learning to work efficiently and constructively with the cladograms in
the modern invertebrate zoological texts, the demand for rote-learning of vast pages
of lists of characteristics becomes completely redundant.
Hence, in this unit, from the lectures you should develop appreciation of some
important themes of the biology unique to particular groups. For example, social
structure is an important aspect of the biology of some insect groups. The selection of
themes is very much subjective and so the particular ones chosen reflect the
personality and experience of each lecturer. But the practical classes must be
integrated with the lectures, because in the practicals you have the opportunity to
learn to recognize diagnostic characteristics serving to delineate each phylum.
So, why study invertebrates? There seems to me to be three important reasons;
others will, no doubt, propose others:
Invertebrates constitute an amazing (in the OED sense of the word) range of diverse
and beautiful animals;
They present an amazing diversity of structures, i.e. of solutions for living, which pose
an exciting intellectual challenge to master:
•
•
Knowledge of their relationships is not fixed: currently they are the focus of
much systematic study integrating systematic and molecular approaches; and
Knowledge of them is important for a wide range of post-university professional
careers.
i
ii
TABLE OF CONTENTS
General Information
Prodromos
Table of contents
Lecture and laboratory timetable
Assessment policies and practices
i
iii
iv
vi
Laboratory exercises, systematic
1&2
3.
4
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Protozoa
Animal tissues, body plans & imaging
Porifera, Cnidaria (Hydrozoa)
Cnidaria (Scyphozoa, Anthozoa)
Platyhelminthes
Mollusca 1
Mollusca 2
Non-segmented coelomate worms
Annelida 2
Lophophorata
Blastocoelomates
Arthropoda: Introduction; chelicerates and myriapods
Arthropoda: Crustacea 1: Malacostraca
Arthropoda: Crustacea 2: Phyllopoda & Maxillopoda
Arthropoda: Insect dissection
Arthropoda: Insect diversity
Echinodermata 1
Echinodermata 2
Protochordates
Larvae
iii
1
21
33
39
43
47
55
67
73
83
87
91
95
101
109
115
129
133
137
143
LECTURE AND LABORATORY SCHEDULE, INVERTEBRATE ZOOLOGY ANIM2203, SEMESTER 1, 2011
Week
#
Commencing
1
28 February
2
07 March
PROTOSTOMES:
Lophotrochozoa
3
14 March
4
21 March
5
28 March
6
04 April
Monday
11 am
Gentilli LT*
Introduction to the
unit:
Overview of the phyla
BK
Animal architecture
JP
Platyhelminthes
BK
Mollusca 1
JP
Nonsegmented worms
& Annelida
JP
Lophophorata
JP
Wednesday
12am
Gentilli LT*
Locomotion at Re<1
BK
Friday
11 am
Gentilli LT*
Protozoa review
BK
Cnidaria
Introduction to
Porifera and Cnidaria JP
JP
Rotifera,
Acanthocephala,
Gnathostomulida,
Gastrotricha
BK
Mollusca 2
JP
Annelida 2
JP
Lophotrochozoa:
synthesis
JP
Practical 2
Wed or Thurs
Zool. Lab.
Protozoa
Imaging
Cnidaria
Porifera/Cnidaria
Cnidaria review
JP
Lophotrochozoa:
Platyhelminthes
Lophotrochozoa
Mollusca: review
JP
Annelida: review
JP
Mollusca 1
Mollusca 2
Nonsegmented worms
& Annelida 1
Annelida 2
Polychaeta
Nematoda,
Priapula
Nematomorpha
Kinorhyncha,
Loricifera
BK
Lophophorata:
Phoronida Brachiopoda
Bryozoa
SUMMATIVE
TEST: PRACTICAL
1
JP: Jane Prince
BK: Brenton Knott
The Gentilli Lecture Theatre is located in the Geography building, Room 1.31.
iv
Practical 1
Mon or Tue
Zool. Lab.
Protozoa
Revision
Formative prac
test
LECTURE AND LABORATORY SCHEDULE, INVERTEBRATE ZOOLOGY ANIM2203, SEMESTER 1, 2011 (Cont.)
PROTOSTOMES:
Ecydosozoa
7
11 April
Arthropoda origins
BK
PROSH
13 April
SUMMATIVE
THEORY TEST
Crustacea 2
BK
EASTER FRIDAY
8
18 April
Crustacea 1
BK
9
02 May
Insecta
BK
DEUTEROSTOMES
10
09 May
Summative Prac test Arthropoda:
1: Feedback
Myriapoda
Cheliceriformes
Nematoda
Tissues/ Imaging
Crustacea
Crustacea
INTRA-SEMESTER STUDY WEEK (NON TEACHING)
Insecta social
Crustacea/Insecta: Insecta
Insecta
organisation
Review
BK
BK
Summative
Theory
test feedback
Deuterostomes &
Echinodermata 1
JP
Invertebrate
chordates
JP
Echinodermata 2
JP
Review: System
solutions to the
problem of becoming
large 1
BK
Exam information
BK
11
16 May
12
23 May
Alternation of
generations
JP
13
30 May
Review: System
solutions to the
problem of becoming
large 2
BK
v
Deuterostome
relationships
JP
Feedback:
summative theory
test
Echinodermata:
Review
JP
Echinodermata 1
Echinodermata 2
‘Protochordates’
Hemichordata and
Chordata
Revision
Semester review
JP
Larval stages
SUMMATIVE TEST:
PRACTICAL 2
Semester review
BK
Revision
Overview, and
Practical test 2
feedback
ASSESSMENT POLICIES AND PRACTICES, 2011
Your final grade in Invertebrate Zoology ANIM2203 will be determined by your
performance involving both theory and practical components. Forty percent of your
marks, overall, will be earned in semester assessments before the formal
examinations in June.
Summative assessment for Invertebrate Zoology 2203 in 2011 will comprise the
following components:
DURING SEMESTER
Assessment
THEORY
PRACTICAL
TOTAL
Due
JUNE EXAMINATION
Value
Assignment
11.March
Summative
theory test
Imaging
exercise
15 April
15%
03 June
10%
Lab test 1
6/7 April
6%
Lab test 2
25/26 May
9%
Exam
TOTAL
Length
Value
Theory
paper
3 hours
30%
50%
Practical
2 hours
25%
50%
55%
100%
5%
45%
Theory assignment Deadline for submission, 5 pm, Friday 11 March.
Set by B. Knott.
Why are there so many phyla of Protista?
The text of the assignment should be no longer than 500 words or about 2, A4
pages; typed, using 12 point Times New Roman font at 1.5 or double spacing.
Standard zoological conventions should be observed (for example, species and
generic names italicised) and sources of information acknowledged. Use the
Harvard format for citing and presenting references. The references provided
elsewhere in this manual (vii-viii) will suffice, particularly the recommended texts.
Late assignments will not be accepted without a legitimate excuse. Consult
with BK BEFORE the due date if you cannot make the deadline.
Practical Imaging assignment
Deadline for submission, 5 pm, Friday 03 June.
Set by J. Prince.
Final details for this assignment will be contained in a handout made available
early in the Semester; preliminary details are included in the notes in Chapter
3 titled “ANIMAL TISSUES, BODY PLANS & IMAGING”.
6
Intra-semester practical test 1:
The practical classes on Wednesday & Thursday, 06 & 07 April, respectively, are set
aside for a summative practical test (i.e., it will be marked and the marks count 6%
towards your total, overall marks) of all the practical material covered in weeks 1-5,
inclusive, in the course.
It will comprise a 1 hour test set in the style and format of the practical
examination sat at the end of the semester and is designed to provide
familiarisation with typical practical examination questions – and to enable you to
earn some marks before the semester ends. You will be notified just before the test
on its structure. It will cover material covered in all previous practical classes.
Intra-semester practical test 2:
The practical classes on Wednesday & Thursday, 25 & 26 May, respectively, are set
aside for a second summative practical test (i.e., it will be marked and the marks
count 9% towards your total, overall marks) of all the practical material covered in
weeks 7-12, inclusive, in the course.
It will comprise a 1 hour test set in the style and format of the practical
examination sat at the end of the semester and is designed to provide
familiarisation with typical practical examination questions – and to enable you to
earn some marks before the semester ends. You will be notified just before the test
on its structure. It will cover material covered in all previous practical classes
during weeks 8-12, inclusive.
Intra-semester theory test:
The lecture time on Friday 15 April is set aside for a summative theory test (i.e., it
will be marked and the marks count 15% towards your total, overall marks) of all
the theory material covered in weeks 1-7, inclusive, in the course.
It will comprise a 45 minute long test, set in the style and format of the theory
examination sat at the end of semester and is designed to provide familiarization
with typical practical examination questions – and to enable you to earn some
marks before the semester ends!
June examinations:
In June, 2011, on dates to be notified from the Examinations Office possibly in
May, there will be two major examinations, as follows:
I. Theory Paper, of 3 hours duration, and contributing 30% to the overall
assessment in the unit. You will be informed during a lecture or tutorial of
the structure of the paper – after it has been set! The venue for the Theory
Paper traditionally has been set by the Examinations Office; and
II. Practical Paper, of 2 hours duration and contributing 25% to the overall
assessment in the unit. The final three Friday classes (20 & 27 May, 03
June) have been designated ‘Semester review’, and it will be possible then to
ask questions concerning the Theory and Practical Papers. The venue for the
Practical examination is the Zoology building.
7
Note: A formative practical assessment is scheduled for 16/17 March. The
assessment will be marked, but the results will not count towards your overall
mark. However, the experience should give you the ‘feel’ for this type of
assessment.
8
Practicals 1 & 2: Protozoa
PRACTICALS 1 & 2:
1
KINGDOM PROTISTA, PROTOZOA
INTRODUCTION
We begin this unit with coverage of entities that, in one sense, are more appropriately
called protists (than animals) – because they lack the multicellular grade of
organization of metazoan animals: they are not metazoans animals. Protists, members
of the Kingdom Protista, constitute a very diverse assemblage of predominantly singlecelled entities with the cells being eukaryotes. Single-celled eukaryote organisms are
now classified in the Kingdom Protista, and Brusca and Brusca (2003) list 17 phyla
within the Kingdom – but this list is by no means complete. The protists are extremely
diverse in form and function, and they grade from forms that are autotrophic (i.e. they
are ‘plant-like’) to forms that are heterotrophic (i.e. they are ‘animal like’) in their
feeding strategies; in between are forms that show a mixture of plant- and animal-like
features. Some are free-living, yet others are parasitic. In this unit, we give a brief
overview of three important categories of protozoan protist.
The eukaryotic cell evolved somewhere about 1,500 million years ago – so protists
constitute a remarkably successful group. Since they have no organ systems – they
are single-celled – they have relied on diverse organelles for their success.
Protozoa refers now to a grade of organization, not to a taxon. Older invertebrate
zoology textbooks after the introductory material often began with a Chapter titled
“Phylum Protozoa”. There is no Phylum Protozoa currently recognized. In those early
texts, protozoans were classified on their organelle used in locomotion of which there
are three main categories, cilia, flagella, pseudopodia. You will not be expected to
learn major amounts of taxonomic detail of protozoans, but you will be expected to
learn to recognize, during the two practical classes, a eukaryotic cell and state whether
it is a ciliate (bearing cilia), a flagellate (moving by flagella) or an amoeboid form (using
pseudopodia to move). It is not a hugely difficult task, once you can use the
microscope efficiently, but it will require being able to recognize the diagnostic
characters, because ciliates are easily confused with small metazoans seen later in the
semester such as miracidia, a juvenile stage of some parasitic platyhelminthes.
Practicals 1 & 2: Protozoa
2
Why do we focus on the methods of movement in protozoans? Because, being very
small (typically ranging in size between 2 – 200 μm in length), their swimming
environment is totally different to ours. This is quantified in terms of the Reynolds
Number, Re, and the Re of protozoans influences their morphology and feeding
strategies. Consequently, the lectures describe the structure and function of the
locomotory organelles and the consequence for feeding. The practical class is used to
exemplify the three locomotory categories.
READING FOR BOTH THE PRACTICAL CLASSES AND THE LECTURES
1. Brusca and Brusca, pp. 126 - 139 (First Edition); pp. 121 - 176 (Second Edition).
2. Rupert and Barnes (6th Edition), pp. 11 - 67.
Read these sections carefully, taking very good care not to become overwhelmed by the
detail - so judge the depth of content required from the lectures and practicals.
I DO NOT EXPECT YOU TO REMEMBER ALL OF THE MASS OF STRUCTURAL OR FUNCTIONAL
DETAIL DEFINING THE HIGHER PROTIST TAXA
OBJECTIVES
On conclusion of the two practicals, you will have begun learning:
1.
how to set up and use a compound microscope at up to 400x magnification;
2.
how to measure size of small specimens using the compound microscope;
3.
to make microscope preparations of living or stained specimens;
4.
to save images of specimens, and edit those images; and
5.
to recognize some of the diagnostic characteristics of protist groups, particularly
of locomotion so that you will be able to classify a protozoan based on its method
of locomotion.
From the lectures, you will be able to discuss:
6.
the structural basis of the three main styles of locomotion and the environmental
constraints; and
7.
the feeding and reproductive biology of protozoans.
Practicals 1 & 2: Protozoa
3
LABORATORY ACTIVITIES
1. Setting up your compound microscope.
It is essential for this course that you learn to use both compound and dissecting
microscopes effectively. Hence, the notes here begin with a description of the
compound microscope available in the laboratory and how to set it up ready for
use; then follows description of two methods for measuring the size of objects in the
field of view.
SETTING UP YOUR COMPOUND MICROSCOPE OLYMPUS CH30
The Olympus CH30 is fitted with self-illumination.
1.
Turn on the illuminator on the right hand side of the microscope.
2.
Rotate the nosepiece until the low power objective is toward the slide (4x, silver
barrel, red stripe).
3.
Place a slide on the stage and adjust its position so that the specimen on the slide
is under the objective. Looking through the eyepiece, use the coarse focus to
focus on the slide.
4.
Lock the coarse focus by turning the right hand inside smooth ring, which has a
lever on it, down, then up until it is finger tight. The procedure locks the coarse
focus adjustment so that it can only lower the stage and not raise it. This is
important because the higher power objectives could be forced through the slide
as they are very close to the slide.
5.
Remove the eyepiece and place it carefully on the clean dry bench.
6.
Adjust the condenser iris using the black lever on the right side of the condenser
aperture so that about 80% of the area seen down the tube lets light through (see
diagram). If the iris is not centred, loosen the set-screw on the right side of the
condenser and gently centre the condenser so that the iris opening is at the
centre of the tube opening. Replace the eyepiece.
7.
Rest the tip of a pencil on the illuminator surface (below the condenser). Adjust
the condenser till the pencil tip is in focus; the microscope should now be set for
optimal performance.
Practicals 1 & 2: Protozoa
4
8.
If the light is too bright decrease the amount by adjusting the brightness of the
illuminator. Do not stop down the condenser iris to reduce the brightness of the
light as this can alter contrast.
9.
Fine focus on the slide. Keep both eyes open. This greatly reduces eye fatigue.
To help you concentrate on what one eye sees in the microscope, be sure that the
other eye looks at the clean bench top or a blank piece of paper.
10. If the microscope has a binocular head (2 eyepieces) there are two additional
adjustments to make. First adjust the distance between the two eyepieces to suit
your eyes. There is an indicator scale between the eyepieces whose reading you
should record so that you can easily readjust the eyepieces. Second, each
eyepiece can be independently focussed. Close one eye and use the fine focus
control to get a sharp image for your open eye. Then close that eye and use the
adjustment on the barrel of the eyepiece to obtain a sharp image for your second
eye.
Practicals 1 & 2: Protozoa
5
CH30 CONTROLS
Practicals 1 & 2: Protozoa
6
Adjusting the interpupillary distance.
While looking through the eyepieces, adjust for
binocular vision until the left and right fields of
view coincide completely. Adjust so that the two
index dots are horizontal.
Note your interpupillary distance on the scale so
that it can be quickly duplicated on any
microscope in the lab.
Adjusting the condenser.
A
B
1. With the 10x objective engaged and the
specimen brought into focus, turn the
field iris diaphragm dial 1 clockwise to
stop down the diaphragm (Figure A).
2. Turn the condenser adjustment height
adjustment knob 2 to bring the field iris
diaphragm image into focus.
3. While gradually opening the field iris
diaphragm image, rotate the two
centring knobs 3 of the compensating
lens to adjust so that the field iris
diaphragm image is centred in the
eyepiece field of view (Figures A and B).
4. To check centration, open the field iris
diaphragm until its image touches the
perimeter of the field of view. If the
image is not precisely inscribed in the
field of view, centre again. (Figure B).
5. When used for actual observation, open
the field iris diaphragm until its image
just circumscribes the field of view.
Practicals 1 & 2: Protozoa
7
Adjusting the aperture iris diaphragm.
C
Since the contrast of microscope specimens
is ordinarily low, setting the condenser
aperture iris diaphragm to 70 –80% of the
N/A of the objective in use is usually
recommended. When necessary, adjust the
ratio by removing the eyepiece and looking
into the eyepiece sleeve while adjusting the
aperture iris diaphragm lever until the image
shown in Figure C is seen.
Methods for measuring objects using the Compound Microscope
There are two basic methods used to measure small objects with the compound
microscope.
Gross measurements using the Vernier Scale on the mechanical stage.
Step one:
Set up your microscope with the object to be measured in the centre of the field of
view.
Using the horizontal adjustment knob on your mechanical stage move the object in
the field of view to the far left or right of the field of view.
Note the reading on the vernier scale to the rear of your mechanical stage, the scale
on the vernier is in millimeters. (1mm=1000microns)
Step two:
Ensure you note the reading against the zero mark on the immoveable scale on the
mechanical stage to obtain the start point on the movable scale.
Move the object to be measured in the field of view from one side of the field of view
to the opposite side of the field of view.
Note the movement of the vernier against the fixed zero mark on the mechanical
stage; this should give you a value in millimeters for:
a. The width of your field of view in microns at that particular magnification.
b. Approx length of the object to be measured using the known field of view
measurement. i.e.: how many times does the object fit into the known field of
view.
c. For example your vernier scale moves 1mm from left to right in step two;
there fore your field of view at that magnification is 1000 microns. If the
Practicals 1 & 2: Protozoa
8
object to be measured takes up one half of your field of view then your object
is approx 500 microns
This method should only be used to obtain approx measurements of reasonably
large objects.
Accurate measurements using a Stage Micrometer and an Eyepiece Graticule.
A Stage Micrometer is a prepared slide that has a 1mm long scale etched on it.
This scale is divided into 10 micron increments.
The Micrometer is placed on the stage right way up as you would use a normal
slide.
An Eyepiece Graticule is a flat glass disc that is placed in the eyepiece of your
microscope; it has a series of etched lines of equal distance apart but has no scale.
The object of the exercise is to calibrate the Eyepiece Graticule for every
magnification available on your microscope using the Stage Micrometer (scale of
known length).
Step One:
Place the Stage Micrometer on the stage of your microscope
Select the magnification of your objective lens, use 10X magnification for this first
exercise
Step Two:
Focus on to the Stage Micrometer scale so that there is a clear image
Move your mechanical stage so that the zero marks of both the Stage Micrometer
and the Eyepiece Graticule is superimposed over each other.
Step Three:
You will note that the scales match exactly
This means that each eyepiece graticule unit is equal to 10 microns at 10X
magnification.
Step Four:
Now move your 20X lens into position.
Move your mechanical stage so that the zero marks of both the Stage Micrometer
and the Eyepiece Graticule is superimposed over each other
You will note that more Eyepiece Graticule units fit into units on the Stage
Micrometer, note this number in your Lab book.
Now repeat this exercise for all lens magnification available on your microscope.
Practicals 1 & 2: Protozoa
9
You should end this exercise with a table that calibrates your microscope eyepiece
for every objective lens magnification.
At 10X magnification one eyepiece graticule unit = 10 microns
At 20X magnification ……..eyepiece graticule units = 10 microns
At 40X magnification……..eyepiece graticule units = 10 microns
Note as the magnification increases the number of eyepiece units increases per 10
micron unit
This calibration only applies to the microscope you are using and must be carried
out again if the type, model or magnification is different.
Once this calibration is complete you will only require the eyepiece graticule to
measure any object at any power magnification available on your microscope.
There are additional computer based methods to measure objects but they require
an imaging camera mounted on a compound microscope, computer with imaging
soft ware and monitor to achieve accurate results.
Work through both methods described and be ready to compare and contrast your
results with the demonstrator and class.
SETTING UP AND USE OF THE OLYMPUS SZ DISSECTING MICROSCOPE
Description general:
The Olympus SZ series microscope is fitted with a binocular head and zoom lens
configuration to allow magnifications up to 40X. The body of the microscope is
mounted on a universal arm; this allows a large vertical working distance up and down
and allows the microscope to be positioned through 360 degrees.
Practicals 1 & 2: Protozoa
10
Operation:
Eyepieces and focusing
There are two 10X eyepieces located on the head of the microscope, each are
independently adjustable for inter pupil distance and the user’s individual diopter
adjustments.
NOTE: Make sure when adjusting the eyepieces that you finish with a circular field of
view, if the field of view is composed of two over-lapping circles you have not adjusted
the inter pupil distance correctly.
To adjust inter pupil distance first grasp the eyepieces and move them apart, look
down one eyepiece and gradually push the other eyepiece inwards, as the two fields of
view integrate slow the movement until you see only one full circular field of view
It is now necessary to focus the microscope on an object to allow the correct
adjustment of your individual diopter settings
1.
Place an object under the microscope and attempt to focus on it.
Practicals 1 & 2: Protozoa
11
2.
Using the focus knobs of the microscope move the body to the upper or lower
limit of the rack DO NOT FORCE THE FOCUS KNOB IF RESISTANCE IS
FELT
3.
If focus is not achieved in step two the horizontal arm of the microscope (the
one with the counter weight) will need to be adjusted up or down. To move
the horizontal arm you will need to loosen the black lock knob located on the
vertical arm, grasp the horizontal arm and lift or lower as required then retighten the lock knob.
4.
Located under the lock knob is a second locking slip ring, ensure you lock
this slip ring when adjustments are complete. This locking system will
prevent the heavy horizontal arm from falling.
5.
You may need to adjust the height a few times to get the correct setting.
6.
When you have adjusted the microscope to the correct height you can then
resolve the object in your field of view using the focus knobs.
7.
You can now adjust the diopter settings on the eyepieces. First focus to gain
the clearest image with both eyes open. Now close one eye and adjust the
diopta by rotating the eyepiece, adjust until you get a clear image for that eye
then repeat for the other eye.
Operation of the Zoom Lens
The Zoom Lens adjustment is located on the body of the microscope and has a
graduated scale up to 4X. This magnification is increased by the 10X eyepieces to
give a maximum 40X magnification.
Horizontal Arm (with counter weight)
The horizontal arm allows the head of the microscope to be moved in or out to cover
a greater area and allows the microscope to be rotated through 360 degrees.
This arm has a lock knob located on the vertical arm and can be locked in any
position.
Other adjustments
Head rotation lock screw is located on the head mounting ring on the body of the
microscope. It is a small silver screw that allows the complete head of the
microscope to rotate.
Practicals 1 & 2: Protozoa
12
Body mounting lock screw is located under the rack assembly and allows the head
and rack assembly to be removed from the Universal Arm. It is a silver knurled
cylinder head screw.
This screw should be checked before the microscope is removed from the bench to
ensure that the head does not detach
AND NOW FOR SOME PROTIST MATERIAL!
MATERIAL AVAILABLE
Slides with ‘e’.
Australian $20.00 note
Vital stains.
Prepared slides:
Paramecium – Unna-Pappenheim and Chatton-Lwoff preparation
Live material:
Cultures of Paramecium, Euglena and Amoeba
Termites (workers) with hypermastigotes
Slides labelled ‘e’ are available in the laboratory. Place one in the light path of the
microscope in the orientation that you naturally read it, and draw the letter ‘e’
viewed through the microscope. What do you notice about your drawing compared
to the original specimen?
What is written on the garment of Mary Reiby on the Australian $20.00 note?
2. Examination of living Paramecium
a. Select a clean dry microscope slide and place a small drop of the culture
medium containing Paramecium on the centre of the slide, using a Pasteur
pipette.
Practicals 1 & 2: Protozoa
13
b. Examine the small drop of fluid on the slide under low power. The protists
present in the fluid will be visible as rapidly moving tiny objects in the fluid. If
none are readily distinguishable, repeat steps a & b until you find some.
c. To examine living protists properly with a compound microscope, you must slow
them down. This is usually done by using 10% methyl cellulose.
Make a small ring on the slide with the viscous methyl cellulose. Add the drop
of water containing protists to the centre of the ring. Select a clean dry
coverslip, place one edge of the coverslip on the slide, and gently lower the
coverslip down onto the methyl cellulose-water drop. This procedure minimizes
the number and size of air bubbles caught under the coverslip. The amount of
fluid on the slide should be enough so that there is fluid under the entire area of
the coverslip, but not so much that the coverslip floats on the fluid and fluid
extends well out from the edges of the coverslip. The protists will gradually slow
down, and should be examinable in a few minutes.
d. Examine the slides you have prepared, first under low power. Use the
mechanical stage to scan systematically the entire area under the cover slip.
When you discover a protist, rotate the microscope nosepiece to the next highest
magnification. Remember to adjust the focus only by the fine focus adjustment.
It may be difficult to keep moving protists in the field of view under high
magnification. Either add more methyl cellulose, or examine the slide later
when continuing diffusion of the methyl cellulose has slowed the protists down.
3. Single species cultures
Cultures of living protists of three groups, the flagellates (Euglena), ciliates
(Paramecium) and rhizopods (Amoeba) are available. Prepare slides from each of the
cultures, sketch on the page overleaf a cell of each kind of protist and note details
of the structures visible, the contractile vacuoles, if present, and the pattern of
locomotion.
Practicals 1 & 2: Protozoa
14
Practicals 1 & 2: Protozoa
15
4. Examination of stained protists.
a. Staining is one way of making the cellular detail clearer, more visible. Even so,
you will not see all detail even using a compound microscope at 1000x
magnification. You will need to develop understanding of what microscope to
use depending on the purpose. Exercise 6 involves using a compound
microscope with phase contrast, for example. In exercise 5, we invite you to
practice staining of Paramecium cells to develop appreciation of how different
stains yield different understanding of cell structure. The drawings in textbooks
make it appear that just one preparation is required to come up with a ‘textbook’ preparation. If only!
For staining generally and in the absence of specific details of methodology,
follow steps a, b, and c from section 2 (pp.3-4), but omit using the methyl
cellulose unless you need to slow down the cells.
b. If you already have a good preparation of some protist under a coverslip on a
slide and you wish to stain the specimen without disturbing the preparation, the
easiest way is to draw stain through under the coverslip. To do this, place a
small drop of the selected stain on the slide at one edge of the coverslip. Place a
small bit of filter or blotting paper on the slide at the opposite side of the
coverslip from the stain. This will draw the stain under the coverslip and mix it
with the fluid containing the protists. Draw the stain to about the centre of the
coverslip.
c. Stain a cell with the vital stain methylene blue, using a cavity slide. Place
small, equal-sized drops, one of methylene blue, one of protist culture, in the
cavity of a cavity slide. Leave for a few minutes and observe.
d. One of the classic demonstrations of protozoology is to use the stain Cong red in
conjunction with yeast to demonstrate digestion in Paramecia.
Using again a cavity slide, place a drop of culture with Paramecium cells in the
Practicals 1 & 2: Protozoa
16
cavity. Stir the drop with a needle that has been dipped (1 cm) into stained
yeast. Place a coverslip over the drop and press down. The drop should be
pink.
Check your preparation 5-10 minutes later. Colour of food vacuoles is bright
red at pH ≥5, and brilliant blue at pH ≤3.
e. Add two small drops of the blue ink/CuSO4/HCl solution to a preparation (as in
‘b’ above).
f.
Examine the stained slides and record which organelles are visible with each
stain in the Summary Table below.
Summary Table: Structures of Paramecium shown by different stains
Pellicle
Stain
Nucleus
Macro
Trichocyst
Cilia
Vacuoles
Micro
Methylene
blue
‘Lees’ solution
Congo red
Chatton-Lwoff
silver line
technique
UnnaPappenheim
technique
Phase contrast
microscope
6. Hypermastigotes
All members of the recently recognized Phylum Parabasilida, ∼300 species, lack
mitochondria. In what kinds of environments would you expect to find them, then?
Practicals 1 & 2: Protozoa
17
Explain.
Some parabasilids are known as Hypermastigotes, and worker termites available in the
laboratory are a good source – from their guts! To extract the protists:
1. Place a worker termite in a drop of insect Ringer solution on a slide;
2. Holding the insect down behind the head using a needle, pull the posterior end
of the abdomen so the gut teases out into the Ringer solution.
Look for protist cells, observing under 10x magnification. Their locomotory organelle is
the flagellum (each hypermastigote is covered by numerous, long flagella).
Practicals 1 & 2: Protozoa
18
7. Phase contrast microscope (demonstration)
•
Phase constrast microscopy reveals detail in unstained living cells by transforming
the differences in the phases of light which pass through media of different optical
densities (which our eyes cannot detect) into differences in intensity of light (which
our eyes can detect).
•
Examine the protists under the phase contrast microscope that has been set up in
the laboratory, and add your observations to the summary table above.
8. Imaging
Depending on how quickly the work is progressing, Mr Gibb will work with small
groups either in the second practical class of this week, or in a practical in a later
week of the semester, demonstrating how to capture images on the digital camera
and download them onto a floppy disc. You will be given a 3.5 inch disc which you
can retain as your own – or (preferably) use you own thumb drive - and use either
fitting in subsequent practical classes, when relevant. It is possible now, using the
appropriate imaging software, to make very accurate measures of surfaces, even of
curved surfaces.
In the meantime, we will try to get a simple, web-based program operating on the
imaging system in the laboratory which will enable accurate measurement of
length, but only in direct line from point-to-point (i.e. not around curves). If this is
achieved, you will be shown how to use this even more accurate method of
measuring lengths.
Record, and note carefully, the levels of accuracy of measurement achieved by the
various methods. What does this tell you about reliability of the measurement?
Practicals 1 & 2: Protozoa
19
OUTCOMES
By the end of teaching on protists, you should be able to:
1.
set up and use a compound microscope;
2.
be able to measure the size of small specimens using the compound microscope;
3.
make microscope preparations of living and stained protists;
4.
save images of specimens;
5.
recognise the diagnostic characteristics of protist groups, particularly of
locomotion.
SELF ASSESSMENT EXERCISE
Make a list of the diagnostic characters of the 3 groups of protists you observed by
light microscopy in the laboratory today.
Flagellates
Ciliates
Rhizopods
Practicals 1 & 2: Protozoa
20
Formative assignment:
Why are there so many phyla of Protista?
The text should be no longer than 500 words or about 2, A4 pages; typed, using 12
point Times New Roman font at 1.5 or double spacing and including images that you
have captured and showing evidence of editorial intervention. Standard zoological
conventions should be observed (for example, species and generic names italicised)
and sources of information acknowledged. Use the Harvard format for citing and
presenting references.
The deadline for submission of the assignment is Friday 11 March.
NB: I do not need a cover sheet with the assignment.
Practical 3: Porifera, Cnidaria (Hydrozoa)
PRACTICAL 3
33
PORIFERA, CNIDARIA 1 (HYDROZOA)
MATERIAL AVAILABLE
Prepared slides:
Porifera: Leucosolenia LS; WM, Scypha LS, CS; Tethya LS
Cnidaria: Hydra CS, WM; Obelia WM; medusa WM; Tubularia WM; Physalia
tentacles.
Preserved or dried specimens:
Porifera: Calcarea, Hexactinellida, Demospongia
Cnidaria: Hydroida, Milleporina, Stylasterina, Chondrophora, Siphonophora
Live material:
Porifera: Demospongia
Cnidaria: Hydroida plus other orders as available
AIMS
1.
To demonstrate the characteristics of the Phylum Porifera and its three classes.
2.
To understand the three types of water current systems seen in sponges.
3.
To demonstrate characteristics of the Cnidaria and the class, Hydrozoa.
4.
To illustrate the life cycle of a typical hydrozoan.
PREPARATORY READING
Read the section LABORATORY TASKS in these notes in conjunction with your text
book, using the diagrams to give you an idea of the structures that you should see in
the material in the practical session. This preparation is essential so that you can be
effective and efficient in carrying out the Laboratory Tasks in the 2 hours of the
practical session.
Practical 3: Porifera, Cnidaria (Hydrozoa)
1.
34
PHYLUM PORIFERA (Pore-bearers or Sponges)
The Porifera are animals that are either asymmetrical or approximating radial symmetry.
They have a porous surface and usually have spicules embedded in their body. The phylum is
divided into three classes. You should know the characteristics of each and be able to identify
them and classify with reasons.
Class Calcarea: Calcareous sponges - includes ascon, sycon & leucon grades of water current
system, calcareous spicules
Class Demospongia: Demosponges - most living sponge species; leucon type of water current
system, silica spicules and/or spongein.
Class Hexactinellida: Glass sponges; no regular canal system, silica spicules; mostly deep
water
Laboratory tasks
a. The Poriferan bauplan
Use the slides labelled Scypha (or Porifera) L.S. T.S. and the diagrams in the textbook.
Examine both the slides and the diagram together to understand the general arrangement of
the sponge body. Be able to locate AND understand the function of the osculum, the
spicules, the spongocoel and the choanocytes.
Use the slide to understand the cell arrangement, in particular, the outer cell layer
(pinacoderm), the inner cell layer (choanoderm) and the cell matrix (mesohyl) in between.
Note that these are cell layers NOT tissue layers. Large unfertilised egg cells are visible in the
mesohyl and there are numerous amphiblastula larvae.
KEEP THIS SLIDE TO GO ON TO THE NEXT SECTION
b.
Water current or aquiferous systems
As sponges grow, their water filtration system becomes increasingly complex. Three levels
of complexity are recognised, relating to the amount of folding shown by the choanoderm.
How does this folding affect the ability of the sponge to filter water?
Examine the slide of Scypha to see the arrangement of radial canals lined with choanocytes.
This arrangement is called the syconoid plan.
i.
Leucosolenia shows the simplest or asconoid body plan. There are no cross sections
available, but revise this level of organisation on the diagrams in the text.
ii. Scypha (=Sycon) shows the syconoid plan. Be able to understand this arrangement in
both LS and TS sections.
iii. The slide “Tethya “ shows the most complex or leuconoid arrangement. The
choanocytes should be around small chambers, but their detail is difficult to distinguish.
KEEP THIS SLIDE TO GO ON TO THE NEXT SECTION.
Practical 3: Porifera, Cnidaria (Hydrozoa)
c.
35
Classification
Sponges are grouped into three classes, the Calcarea, Hexactinellida, and Demospongia, on
the basis of skeletal structure. Most sponges belong to the Demospongia.
i.
On the cross section of Tethya (Demospongia), notice the parts of spicules cut up during
the sectioning process. These spicules and their form are the diagnostic features that
reveal that the slide is of a sponge. The bulk of the section shows pink-staining tissue,
mostly spongin skeletal material, and cells in the mesohyl. Examine the whole mount of
Leucosolenia (Calcarea) and compare the form of the spicules.
ii. To distinguish between the spicules of the Calcarea and Demospongia, you should take a
minute portion of a preserved specimen of each and place them well apart on a
microscope slide. Add one drop of 1N HCl and observe the reaction. Explain the result.
iii. Examine the preserved specimens of the glass sponges (Hexactinellida); you should be
able to distinguish these kinds of sponges from the others.
iv. Examine the range of preserved, dried and living material to familiarise yourselves with
the gross morphology of all three classes.
2.
PHYLUM CNIDARIA
The phylum Cnidaria is divided into four classes. Again you must know the characteristics of
each and be able to identify them with reasons.
Class Hydrozoa: hydroids, siphonophores, hydrocorals, hydromedusae, etc.
Class Anthozoa: anemones, corals, soft corals, gorgonians, sea fans, sea pens, etc.
Class Scyphozoa: jellyfish
Class Cubozoa: sea wasps (box jellyfish)
Laboratory tasks
1.
Class 1: Hydrozoa
Hydrozoans consist of a large variety of sizes and kinds of animals, which almost all exist
primarily as polyps, with a small inconspicuous medusoid stage. We refer to them as
hydroids, fire weeds and fire corals. The polyps (= zooids) are typically small, with solid
tentacles, and are often polymorphic, with individual polyps modified for different functions:
feeding (gastrozooids), reproduction (gonozooids) or defence (dactylozooids).
a. Basic structure of a hydrozoan polyp (= zooid)
Examine a whole mount of the solitary polyp, Hydra. Use them to understand the basic
structure of cnidarian polyps, in particular, the stalk and basal disc, the mouth surrounded by
tentacles. Notice that the tentacles are not hollow, but made up of columns of cells. This
distinguishes hydrozoan polyps from anthozoan polyps and zooids of other phyla.
Practical 3: Porifera, Cnidaria (Hydrozoa)
36
On a cross section of Hydra, make out the diploblastic structure, with a thin mesoglea
between the outer epiderm and the inner gastroderm, surrounding the central gut or
coelenteron.
All cnidarians are characterised by the possession of cnidae: stinging cells, usually
concentrated on tentacles. Can you find these cells on the Hydra wm or c.s.?
b.
Structure of hydrozoan colonies
Hydra is somewhat of an exception amongst hydrozoans. Most species exist as colonies,
rather than single individuals, and many show specialisation of polyps (zooids) for different
functions: gastrozooids or hydranths, gonozooids or blastostyles, and dactylozooids.
Examine whole mount preparation of the colonial species Obelia. The zooids are connected
by a hollow diploblastic stem, the coenosarc, which secretes a chitinous covering - the
perisarc. In Obelia, the perisarc extends around the gastrozooids and gonozooids. Because
of this characteristic, Obelia is referred to as a thecate hydroid.
c.
Characterisitics of the hydrozoan medusa
In Obelia (and many other cnidarians), the free swimming medusa are released from the
gonozooids by asexual budding. The medusa themselves reproduce sexually, releasing
gametes that fertilise to form a solid planula larvae. These will settle and grow into new
polyp colonies. Thus, the life cycle consists of both asexually reproducing polyp stage, and a
sexually reproducing medusa stage. This is called alternation of generations.
Examine a slide of the free-living medusa of Obelia which develops as an offshoot of the
gonozooids. Note its small size. With the help of your textbook, identify mouth and
manubrium, tentacles and gonads.
d.
Hydrozoan diversity
i.
Other hydroids
Examine any live hydroids available. Some of these may be Obelia, but others may be other
species. Look for the characteristics you have noted in Obelia. How do the other species
differ? If there is no live material available, examine the slide labelled Tubularia WM and try
to interpret what you see.
ii. The hydrocorals: polyps in elaborate skeletal systems
Some hydrozoans have massive calcareous skeletons. Examine the skeleton of a milliporid,
which has large pores for the gastrozooids (the gastropores) and smaller pores for the
dactylozooids (the dactylopores) arranged in a circle around the gastrozooid pore.
Practical 3: Porifera, Cnidaria (Hydrozoa)
37
iii. Large colonial hydrozoans with a float
Some hydrozoan colonies drift on the water surface, buoyed by a float, with their polyps
trailing down into the water. Examine preserved specimens of Vellella or Porpita. Identify
the float, the gastrozooids, gonozooids and dactylozooids.
Examine a preserved specimen of Physalia and observe the gas filled float or pneumatophore
and the three types of zooids. Examine the slide labelled “Physalia tentacle” to observe the
batteries of cnidae present on the dactylozooids.
Outcomes
1.
You will be familiar with the basic structure of a sponge and be able to recognize the
characteristic spicules and spongin that make up the skeletal elements of sponges.
2.
You will be able to recognize and identify individuals of the three classes of Porifera
3.
You will be able to recognize hydrozoan polyps, including feeding and reproductive
forms that occur individually or in colonies, and hydrozoan medusae
4.
You will be familiar with the massive calcium carbonate skeletons of hydrozoan corals.
5.
You will be able to recognize the nematocysts, diagnostic organelles of cnidarians.
Practical 3: Porifera, Cnidaria (Hydrozoa)
38
Practical 4: Cnidaria: Scyphozoa, Anthozoa
PRACTICAL 4
39
CNIDARIA 2 (SCYPHOZOA, ANTHOZOA)
MATERIAL AVAILABLE
Prepared slides:
Scyphozoa: Aurelia – planula, hydrotuba, strobila, ephyra,
Anthozoa: Alcyonium – polyp, TS, Alcyonacia - TS, LS,
Pocillopora damicornis - sperm, egg and planula, slides and photos
Anemone – TS
Preserved material
Cubozoa
Anthozoa: Alcyonacea, Gorgonacea, Pennatulacea,
Actinaria, Scleractinia, Zoanthidea
Live specimens
Scyphozoa: Aurelia, Phyllorhiza punctata
Anthozoa: an array of soft and stony corals and anemones.
AIMS
1.
To illustrate the distinguishing characters of the Classes Scyphozoa, Cubozoa and
Anthozoa of the Phylum Cnidaria.
2.
To demonstrate a typical scyphozoan life cycle
PREPARATORY READING
1.
Revise diagnostic characters and classification of Cnidaria in this manual and in your
textbook.
2.
Read these laboratory notes, and the systemic resume of Scyphozoa, Cubozoa and
Anthozoa in your textbook.
Practical 4: Cnidaria: Scyphozoa, Anthozoa
40
LABORATORY TASKS
2. Class Scyphozoa
Scyphozoans are cnidarians with a predominating medusoid stage and a reduced polyp stage.
We refer to them as jellyfish, due to the thick layer of jelly-like mesoglea between the two
body layers: the epidermis and gastrodermis, derived from the ectoderm and endoderm
respectively.
a.
The structure of a typical syphozoan medusa
The transparent, white jellyfish that occurs in the Swan River belongs to the genus Aurelia.
Place a live Aurelia in a bowl of river water and observe:
the jelly-like consistency of its body, a result of a massive mesoglea layer
the conspicuous gonads bordering the gastric pouches with gastric filaments,
the radial and circular canal system,
the marginal tentacles and notches with sense organs (lappets and tentaculocysts or
rhopalia).
Turn the animal over and observe the mouth, the four oral arms with grooves and the
subgenital pits. Note the absence of a true velum.
Watch the Aurelia move, and describe how this is accomplished.
b.
The life cycle of Aurelia
Aurelia shows the typical cnidarian life cycle, alternating between an asexually reproducing
polyp and a sexually reproducing medusa. Examine prepared slides of the life cycle of
Aurelia including planula, scyphistoma, strobila and ephyra and find out how they fit
together to form the complete lifecycle.
c. Other scyphozoans
The second, more conspicuous brown jellyfish that occurs in the Swan River is called
Phyllorhiza punctata. Place a live or preserved specimen of Phyllorhiza punctata in a bowl
with the appropriate fluid and examine the structure of the oral arms. In contrast to Aurelia,
the oral arms are fused and the oral grooves are closed canals for most of their length.
3.
Class Cubozoa
These are the box jellyfish, ranging in size from the deadly sea-wasp of northern Australia to
tiny stingers like those common on metropolitan beaches. The medusa bell is square in cross
section; with tentacles in groups at the four corners of the bell. Examine the preserved
material available and diagrams in your text, including that of the life cycle.
Practical 4: Cnidaria: Scyphozoa, Anthozoa
4.
41
Class Anthozoa
Anthozoans exist as polyps. There is no medusa stage. The polyps are generally large and,
unlike hydrozoans polyps, are not differentiated into different types to perform different
functions. The tentacles are hollow and an ectodermal stomodeum extends into the
coelenteron, which is divided by longitudinal filaments or mesenteries.
There are two major subclasses of anthozoans, the Alcyonaria or Octocorallia (eight fold
symmetry), and the Zoantharia or Hexacorallia (six fold symmetry), distinguished by the
number and form of their tentacles and mesenteries. You are required to be able to
recognise and differentiate these two groups. Their distinguishing features can be seen as
follows:
Subclass Alcyonaria or Octocorallia:
These anthozoans have eight pinnate tentacles and eight internal mesenteries.
a. Examine living or preserved specimens of the alcyonarian Alcyonium, together with the
slide "Alcyonium polyps".. The polyps are <1 cm long, projecting from the surface of the
colony. You should be able to see the eight tentacles on each polyp. Note that the
tentacles are pinnate, that is, have projections from their main axis. This is in contrast to
the simple non-pinnate, tentacles of Zoantharian polyps..
.
The column of the polyp shows, at the tentacle end, denser staining. This is indicative of
the stomodaeum, the tubular extension within the polyps, from the opening of the mouth
at the base of the tentacles. Below the stomodaeum, radial mesenteries extend from the
wall of the polyp towards the centre. The central edges of the mesenteries have crenulated
gastric filaments.
b. Examine the slide Alcyonacea TS. This is a cross section of a colony with the polyps
embedded in the colony's matrix. The sections are cut below the stomodaeum, and show
the mesenteries projecting into the coelenteron. Count the mesenteries. There should be
eight, the same number as the tentacles, and similarly diagnostic of the subclass.
Subclass Zoantharia or Hexacorallia:
This group of anthozoans has simple non-pinnate tentacles in multiples of six
c. Examine a slide of Pocillopora damicornis labelled S1 from the slide box labelled
"Pocillopora - stomodaeum and mesenteries". These are tangential sections through the
polyps of a colonial coral. Find a polyp sectioned through the stomodaeum and count the
mesenteries extending from polyp’s wall to stomodaeum: there should be a multiple of
six, the diagnostic character of the zoantharians.
d. Look next at the slides labelled "anemone T-S" which are cross sections through the
stomodaeum showing a more complex pattern of mesenterial arrangement. The primary
mesenteries here come in pairs. (How many?) Notice the swellings on the mesenteries,
these are the muscles. Note the mesenteric filaments.
Practical 4: Cnidaria: Scyphozoa, Anthozoa
42
Anthozoan life cycles
Anthozoans differ from most other cnidarians in NOT exhibiting a polyphasic life cycle.
There is no medusa stage and polyps are able to reproduce both asexually and sexually.
Mature polyps develop gonads and release sperm and/or eggs into the water column. What is
this life history strategy called? They may also bud planulae larvae asexually if conditions
are favourable. What is the term for animals that use both these reproductive strategies
opportunistically and why might they do it?
e. Your demonstrator will interpret the structure of Pocillopora polyps with the class to
show examples of eggs, sperm and planula larvae within the polyps.
Anthozoan diversity
Anthozoa contains many types and species of cnidarians that will be familiar to you. These
include the soft corals, sea fans, sea anemones and hard corals. Examine a range of dried,
preserved and living specimens and note the distinguishing characteristics that make them
members of the class Anthozoa and the subclass Alcyonaria or Zoantharia.
Outcomes
1.
You will be able to recognize medusae that belong to the Class Scyphozoa, and to the
class Cubozoa.
2.
You will be able to recognize and name the stages in the life cycle of Aurelia, and be
able to describe the sequence that the stages have in life cycle and how they were
produced (i.e. sexually or asexually).
3.
You will be able to recognize in whole animals, and in histological slides, anthozoan
polyps (as distinct from hydrozoan polyps, and other kinds of polyps and zooids), that
belong to the two main groups of Anthozoa: octocorallians and hexacorallians.
4.
You will be familiar with the general appearance of animals that belong to the
Octocorallia (= Alcyonaria), and to the Hexacorallia (= Zoantharia) and be able to
distinguish between the two.
SELF ASSESSMENT EXERCISE
1. Fill in the table provided to compare and contrast the characters of hydrozoans,
scyphozoan and cubozoan medusae.
2. Fill in a similar table to compare and contrast the characters of hydrozoan and anthozoan
polyps.
3. Explain how to be sure that a massive calcium carbonate skeleton is a true coral
(Anthozoa), and not a hydrocoral (Hydrozoa).
Practical 5: Platyhelminthes
PRACTICAL 5
43
PHYLUM: PLATYHELMINTHES
MATERIAL AVAILABLE
Prepared slides
Bdelloura WM, Fasciola hepatica WM, CS, miracidium, redia, and cercaria
Slide C1, Taenia scolex, Bothriocephalus scolex, cestode plerocercoid,
cysticercus, cysticeroid and hydatid. Slides C1 & T 14
Preserved specimens
Fasciola hepatica, Taenia solium
Cestode cysticercus, coenurus and hydatid
AIMS
1. To illustrate the characteristics of the phylum Platyhelminthes and the four
classes: Turbellaria, Digenea, Monogenea and Cestoda;
2. To introduce you to intermediate stages in the life histories of some parasitic
platyhelminths.
There will be post-lab opportunities to test your recognition of diagnostic characters
on new material.
PREPARATORY READING
Brusca and Brusca pp. 279-311 (First Edition), 285-318 (Second Edition).
Rupert and Barnes pp. 203 – 253, particularly pp. 211 – 253.
LABORATORY TASKS
1. Turbellaria
i
Examine the prepared slides of Bdelloura. Try to identify the mouth and
muscular pharynx, the three-branched gut and reproductive system. Use
diagrams provided and/or in your text to help you interpret the slides.
2. Digenetic trematodes
i.
Examine the prepared whole mounts of the liver fluke, Fasciola hepatica.
Use the diagrams in your textbook to identify the structures associated with
the digestive and reproductive systems. You may need to look at more than
one slide to see all structures clearly.
ii. Identify these same structures on a cross section of Fasciola, noting also the
triploblastic cell arrangement, the epidermis with spines and the position of
the muscle layers.
Practical 5: Platyhelminthes
44
iii. Examine the prepared slides of the miracidium, redia and cercaria of
Fasciola, referring to diagrams in your textbook for a general account of the
life cycle of digeneans.
3. Monogenea
i.
Examine the prepared slide labelled T14 and note the presence of a large
posterior attachment organ or haptor, in this case subdivided into numerous
small suckers. There is no circum-oral sucker but two small eversible
suckers in the buccal cavity.
4. Cestoda
i.
Examine the prepared slide labelled Taenia -example 1 and identify the body
or strobila with its string of proglottids, the neck, and the head or scolex.
On the scolex find the anterior rostellum armed with hooks and four cupshaped suckers or acetabula. The proglottids are produced by transverse
constrictions at the neck region. The proglottids farther down the body are
older and larger and have developed a hermaphrodite reproductive system.
Select a section of the strobila where the reproductive system is mature but
not yet obliterated by eggs and, using Brusca and Brusca, Ruppert & Barnes
or Barnes, identify all the structures of the reproductive system. The largest
proglottids show the development after fertilization. The uterus contains
thousands of eggs and enlarges until it fills most of the proglottid. The rest
of the reproductive system degenerates and the proglottid detaches and/or
bursts.
ii. Compare the slide of Taenia with the whole mounts of Bothriocephalus example 2. Note the bothria in place of acetabula. Refer to Brusca and
Brusca, Ruppert and Barnes or Barnes and display diagrams for the
structure of other attachment organs in the Cestoda. Bothriocephalus has a
limited number of proglottids and eggs are released through the uterine pore
rather than by rupture of the proglottid.
iii Cestode life histories are complex and usually involve more than one host.
When eggs are released from the body of the definitive host they either hatch
into a six-hooked ciliated larva, or develop into a larval stage within the egg.
In both cases no further development takes place until the larva is ingested
by a suitable intermediate host. It then develops into a metacestode.
Practical 5: Platyhelminthes
45
The metacestode stage will only develop if the intermediate host is eaten by
the definitive host in which case it lodges in the alimentary canal, buds
proglottids and becomes sexually mature.
There are a variety of types of metacestode. Examine all the available slide
and preserved material of the metacestode stage noting differences and
similarities among the various forms. Some names of metacestodes (which
you don’t need to know) include:
a. Procercoid: A solid embryo (without a bladder), that develops from the six
hooked larva, with a tail bearing the now useless six hooks. This
develops slits (the bothria), loses its tail and is then called a plerocercoid,
which is virtually just a scolex and neck.
b. Cysticercus: A bladder containing fluid into which projects the
introverted head of the metacestode. This everts in the alimentary canal
of the definitive host.
c. Cysticercoid: Head of metacestode retracted, not inverted, into a minute
bladder, merely forming a sheath for scolex.
d. Coenurus: Numerous scolices inverted into a single bladder.
e. Hydatid: Primary bladder buds many secondary bladders which in turn
bud scolices. When the primary bladder is cut open, the numerous
secondary bladders appear as numerous granular bodies termed hydatid
sand.
5. Revision slides
With reference to the following key, identify to class, family and/or genus the
slides labelled T4, T6, T11, T(13 and 14), T17, T26, T30, T40, C1, C(4 and 5),
C10, C27 and C30 and have your identifications checked by your demonstrator.
OUTCOMES
1.
You will be familiar with the characteristics of the four main classes of the
Platyhelminthes and be able to compare and contrast between them.
2.
You will be familiar with the key on the following pages and with the
terminology they use, and be able to use them to identify platyhelminths.
Practical 5: Platyhelminthes
46
Practical 6: Mollusca 1
PRACTICAL 6
47
PHYLUM: MOLLUSCA 1
MATERIAL AVAILABLE
Preserved specimens:
Whole cepalopods, plus shells of chitons, gastropods, cephalopods,
bivalves and scaphopods
Live or narcotised material:
Specimens of Haliotus or Turbo to be shared.
An array of living molluscs.
AIMS
1.
To illustrate the basic molluscan characteristics using a primitive gastropod.
2.
To develop expertise in detailed invertebrate dissection.
3.
To demonstrate the diversity of form within and between the five major classes
of molluscs.
PREPARATORY READING
Brusca, R.C. and Brusca, G.J. (2003) Invertebrates, 2nd edition. Sinauer
Associates, Massachusetts, Chapter 20.
LABORATORY TASKS
A. The basic molluscan structure as shown by a primitive gastropod
Work in pairs. Select a narcotized specimen of the abalone Haliotis roei and follow
the dissection guide, identifying all structures. Refer continually to the basic
molluscan characters listed in your textbook, making sure you understand how
they are expressed in this specimen. Label the diagrams provided but make your
own notes and sketches as well.
Dissection guide for Haliotis roei (Subclass Prosobranchia, Order
Archeogastropoda)
Before removing the animal from its shell, note the line of perforations along the left
side. These allow water and waste products to escape from the mantle cavity.
Without damaging the mantle and viscera, scrape the mantle away from the shell,
beginning on the right side; then, cut carefully through the shell muscle with your
scalpel to release the animal.
Practical 6: Mollusca 1
48
External Anatomy
Most molluscs consist of a head, foot and visceral mass. Identify these three
regions on the abalone. The head bears two pairs of tentacles, the more lateral
pair with eyes at their tips. The mouth is on a ventrally directed muscular snout,
below which the large muscular foot is cleft. The foot is encircled by a dorsal collar,
the epipodium, bearing numerous tactile tentacles. The visceral mass is coiled
around the left side of the large shell muscle and covered by the mantle. Find the
following structures WITHOUT cutting into the animal.
The mantle cavity opens anteriorly (Why?), and is on the left side of the animal. Its
roof is deeply cleft, corresponding with the shell perforations, and along the cleft are
several mantle tentacles. Through the roof of the mantle cavity, make out the
positions of the two ctenidia (gills) and the mucous gland, and the rectum with
the anus just at the base of the mantle cleft.
Immediately posterior to the mantle cavity, adjacent to the mucous gland, is the
pale brown left kidney. Behind this lies the translucent pericardium and the
posterior end of the right kidney which runs down the right side of the mantle cavity
and curves around the back of the pericardium. Behind and to the right is the
visceral mass consisting of a brown digestive gland and a diffuse gonad - either a
green ovary or a cream testis.
Practical 6: Mollusca 1
49
Internal Anatomy
1.
Blood system
Through the pericardial wall it should be possible to make out the position of the
atria and ventricle. Blood vessels enter the pericardium from the gills (branchial
vessels) and leave to supply blood to the body via the small anterior aorta, to the
mantle cavity, and a larger posterior aorta, giving branches to the head and
visceral mass.
Work with fine forceps and carefully remove the pericardium to expose the heart.
The two thin-walled atria lie to each side of the central muscular ventricle which
envelops the rectum. The posterior aorta should be visible.
2.
Mantle Cavity
Work forward from the heart and keep to the right of the rectum. Cut the roof of
the mantle cavity through to the base of the mantle cleft. Find the mucous gland
and the two ctenidia and identify the branchial vessels on each side of the ctenidia.
Some species (but not this one!) have a small cream coloured area, the osphradium,
at the anterior end of each gill to "taste" the incoming water. Trace the rectum from
the heart to the anus.
3.
The two kidneys are sac-like structures with spongy walls and are in close
association with the heart. The kidneys open through small pores (nephridiopores)
ventral to the base of the rectum in the mantle cavity but these are not easily seen.
Anteriorly, the right kidney lies adjacent to the gonad, and eggs or sperm pass into
the kidney through a simple opening in the kidney wall to be released via the kidney
opening.
Practical 6: Mollusca 1
4.
50
Alimentary canal and nervous system
The alimentary canal is difficult to dissect because of its thin walls. Beginning just
anterior to the shell muscle, make a shallow cut towards the mouth and pull the
skin off the head region. This should expose the top of the buccal cavity and the
anterior end of the oesophagus.
Towards the mouth find the nerve ring lying across the top of the buccal cavity.
The nerve ring is made up of three interconnecting pairs of ganglia, effectively the
“brain”. Another ring below the oesophagus links more ganglia into the nerve ring.
It is unlikely you will be able to differentiate these ganglia. Immediately behind the
nerve ring are the salivary glands.
Remove the roof of the buccal cavity to see the radula lying on top of the
odontophore, just posterior to a pair of immoveable horny plates against which the
radula chews the food. The radula itself is a long flexible chitonous rasp, most of
which lies in a long tube, the radula sheath, entering the buccal cavity ventrally.
The sheath ends in the radular sac that secretes the radula. Remove the radula
and observe it under the microscope. Note the repeated tooth rows and the
differentiation of teeth within the rows. Note their structure.
Practical 6: Mollusca 1
4.
51
Alimentary canal and nervous system (cont.)
Try to follow the oesophagus posteriorly from the buccal mass down around the
shell muscle to the large extended crop and the stomach with its spiral caecum at
the posterior end of the visceral mass. The oesophagus passes ventral to the
intestine which runs forward from the stomach towards the head then loops
backwards to the level of the pericardium and then forward again to pass through
the ventricle and into the mantle cavity. The presence of digestive gland and gonad
makes the alimentary canal difficult to trace. Work backwards from the rectum and
posteriorly from the oesophagus to get a general idea of the layout of the alimentary
canal.
Practical 6: Mollusca 1
B.
52
The diversity of molluscs
Survey the living and preserved molluscs and mollusc shells that are available in
the laboratory. Fill in the following table to compare and contrast the five common
classes. Make sure the table is complete to provide you a resource for revision
purposes.
OUTCOMES
1.
You will be able to locate all the major structures found in a typical mollusc
and gastropod.
2.
You will know the general appearance, structure and function of five of the
eight classes of molluscs.
Practical 6: Mollusca 1
53
Characteristics of five classes of Mollusca
Class
Polyplacophora
Gastropoda
Cephalopoda
Bivalvia
Scaphopoda
Foot
Shell
Head
Mantle Cavity
Radula
Other notes
Practical 6: Mollusca 1
54
Practical 7: Mollusca 2
PRACTICAL 7
55
PHYLUM MOLLUSCA 2
MATERIAL AVAILABLE
Preserved specimens:
Frozen squid – 2 per 3 students
Narcotised material:
Mytilus – 1 per 2 students
AIMS:
1.
To illustrate the internal anatomy of bivalves and cephalopods.
2.
To make comparisons between the anatomy of gastropods, bivalves and
cephalopods.
PREPARATORY READING:
Revise relevant sections of your textbook.
Practical 7: Mollusca 2
56
LABORATORY TASKS:
1. Bivalvia
Examine a narcotized Mytilus. What characteristics allow you to immediately
classify this as:
a) a mollusc, and
b) a bivalve?
With reference to the diagrams opposite, establish what is the anterior and
posterior, dorsal and ventral, and right and left of the animal. Carefully remove the
right shell valve by separating the mantle from the shell and cutting through the
muscles. Place the animal in a small bowl of seawater.
The two folds of the mantle completely enclose the animal. Before removing the
upper fold, examine the pericardium, seen as a window in the mantle. The heart
consists of an elongated ventricle, surrounding the intestine, and two sac-like
atria. With the specimen under a dissecting microscope, remove the pericardium to
find these structures.
Cut away the free flap of the mantle to expose the mantle cavity. The most
prominent structures are the curtain-like gills or ctenidia. Examine the ctenidia
closely. Each ctenidium consists of two flaps of ciliated tissue, which hang down
into the mantle cavity (two demibranchs for each ctenidium). You may be able to
see small particles moving over the surface and along the ventral margins of the
ctenidia. Cut away a small section of one demibranch, place it in seawater and
observe it under higher power.
Cut away the ctenidia to expose the visceral mass. Using the diagrams, revise the
internal anatomy, identifying the mouth and labial palps, foot and byssal threads,
kidney, gonad and urino-genital papilla, anus and exhalent siphon.
Working forward from the intestine, follow the alimentary canal through the
digestive gland and find the expanded stomach, which contains a long thin
crystalline style. This rubs against a thin chitinous gastric shield at the anterior
end of the stomach. Entering the stomach is a short oesophagus running from the
mouth, which is surrounded by two pairs of labial palps.
Note: there is no radula.
Practical 7: Mollusca 2
57
Practical 7: Mollusca 2
2. Cephalopoda
Dissection of a squid (species as available) (Cephalopoda: Coleoidea; Teuthoidea).
Place a thawed specimen on a dissecting tray. Think back again to the general
characteristics of molluscs. What makes this animal a mollusc? What are the
obvious features that classify this specimen as a cephalopod?
EXTERNAL ANATOMY
•
The body can be divided into a head
region bearing the arms and
tentacles, and a pointed visceral
hump with lateral fins. It is
generally considered that the foot is
incorporated into the head region,
the anterior end of which is
represented by the arms and
tentacles and the posterior end by
the siphon.
•
In the head region, distinguish the
eight pointed arms (for holding the
prey), each with two rows of stalked
suckers along its inner side; the two
larger tentacles (to catch prey) with
stalked suckers only at the tips; the
mouth within the ring of arms; the
two horny, beak-like jaws
protruding from the mouth; the pair
of large, well-developed eyes; and,
ventrally, the tubular siphon
(through which water is expelled
from the mantle cavity).
•
The visceral hump is long and
pointed, and bears two lateral fins
for swimming forwards. These fins,
extensions of the mantle, contain
longitudinal, vertical, and transverse
muscle-sheets. Notice the circular
opening around the back of the
head, which leads into the mantle
cavity. Also notice that the skin,
especially dorsally, contains
innumerable dark spots, the
chromatophores (which are
pigment cells surrounded by muscle
strands causing the cell to expand
or contract during the process of
colour change).
58
Practical 7: Mollusca 2
59
INTERNAL ANATOMY
Part of the dissection described below is carried out from the ventral side and part
from the dorsal side. To avoid confusion, it should be constantly borne in mind
that the terms left and right, and dorsal and ventral, refer strictly to the animal and
this orientation should be established before you begin to cut into the specimen.
Mantle cavity
•
To open the mantle cavity, cut along
the full length of the visceral hump
just to one side of the mid-ventral
line. Such a cut passes to one side
of the median septum, which
separates the posterior part of the
mantle cavity into the left and right
halves. Also open the siphon by a
longitudinal cut. At the anterior end
of the mantle cavity find the three
cartilaginous ridges that fit into
cartilaginous grooves on the side of
the siphon and the mid-dorsal line
of the body. These lock together to
keep the two inhalant currents
separate from the single exhalent
current passing out through the
ventral siphon. Identify the pair of
sac-like valves lateral to the siphon
that prevent the inflow of water.
•
Find the two ctenidia, placed so
that the inhalant current will pass
directly over them; the transparent
rectum ending in the anus at the
base of the siphon; the anal valves
at the sides of the anus; and the
large silvery black inksac passing
dorsal to and then entering the
rectum.
•
There is a very thin membrane
covering the visceral mass, which
needs to be at least partly removed
in order to see the underlying
structures clearly. Remove the
membrane carefully, remembering it
is the same colour and texture as
many of the structures themselves.
Practical 7: Mollusca 2
60
You will know if the animal is male or female by the presence or absence of
nidamental glands lying just behind the inksac. These glands occur only in females
and function to secrete an elastic membrane over each egg.
Reproductive and Excretory systems:
Female
•
Identify the large white nidamental
glands; the oviduct leading from the
coelom to the mantle cavity; the large
oviducal gland at the base of the
oviduct that secretes the outer
eggshell and may be attached to a
large gelatinous mass, and the single
posterior ovary.
•
The nidamental glands lie directly on
top of the renal sacs, which are
usually destroyed when these glands
are removed. It may be possible to see
the translucent sacs opening at
papillae lateral to the base of the
rectum if you gently move the glands
to one side. Anterior to and slightly
beneath the nidamental glands are
the speckled orange accessory
nidamental glands. Remove these
as well.
Practical 7: Mollusca 2
Reproductive and Excretory systems:
Male
•
Males have no accessory glands and so the
translucent renal sacs may (but usually
arenot!) visible directly posterior to the inksac,
with the openings on papillae at the anterior
end. (This varies between species.). The
anterior end of the vas deferens should be
visible to the left of the inksac. However, the
main part of the sperm-duct is obscured by
the left branchial heart. Separate this duct
from the adjacent blood vessels, and trace the
course followed by the spermatozoa.
•
The single testis has a longitudinal, slitlike opening in its ventral surface
through which the spermatozoa escape
into the coelom. They are then collected
by a ciliated funnel, and passed into the
sperm-bulb at the posterior end of the
vas deferens. From the sperm-bulb the
highly convoluted vas deferens runs
forwards to the spermatophoric gland
(which secretes the membranes of the
spermatophore around groups of
spermatozoa). The fully formed
spermatophores are passed back
through the middle region of the vas
deferens to be stored in the
spermatophoric sac, from which the
anterior end of the vas deferens passes
forward. During copulation the left
ventral (or hectocotylised) arm picks the
spermatophores from the opening of the
vas deferens and transfers them to the
female. Notice that on this arm the
distal suckers are replaced by long
papillae.
61
Practical 7: Mollusca 2
Heart and blood vessels
Pull away the membranes of the renal sac and pericardium. This exposes two
branchial hearts at the bases of the ctenidia and the darker yellowish median
heart. From behind the inksac, the large cephalic vein emerges and splits into
two branches, which pass into the branchial hearts. These vessels lie within the
renal sacs and their walls are covered with renal tissue. From the branchial
hearts, afferent branchial veins pass to the ctenidia and the efferent branchial
veins return oxygenated blood to the median heart.
62
Practical 7: Mollusca 2
63
Alimentary Canal
•
•
•
Remove the ctenidia and the branchial
hearts and displace the median heart,
inksac and rectum to your right to
uncover the middle region of the
alimentary canal. The accessory
digestive glands lie behind the position
of the median heart and the digestive
glands are anterior to them running up
towards the head. Three thin walled
tubes emerge from the digestive gland
in this region: the duct of the digestive
gland, the anterior aorta and the
posterior end of the oesophagus, which
enters the sac-like stomach on the
(animal's) right side. At its left anterior
end the stomach is linked to the long,
thin-walled caecum and with a short
intestine that passes under the
median heart and into the rectum. The
duct of the digestive gland, which is
surrounded by the tissue of the
accessory digestive gland, enters the
anterior end of the caecum.
Follow the oesophagus towards the
mouth by carefully removing the
digestive gland. At the anterior end of
the digestive gland you may be able to
distinguish the median salivary gland
(this secretes poison and not digestive
enzymes) immediately posterior to the
skull. Cut away the tentacles and
remove the muscles from the region
between the eyes until the cartilage of
the skull is reached and finally dissect
away the muscles and connective tissue
between the skull and the mouth until
the buccal mass is exposed.
The buccal mass is enclosed in a large
buccal sinus, which is the swollen
anterior end of the cephalic vein. The
oesophagus passes forwards through
the skull, and, together with the duct of
the median salivary gland, enters the
posterior end of the buccal mass.
Lateral to these points of junction are
the lateral salivary glands (also
secreting poison)
•
Cut open the buccal mass.
Distinguish the two beak-like jaws;
the ventral radula, the posterior end
of which is enclosed in a radula sac;
and the tongue, which is anteroventral to the radula. Remove the
radula and examine it under a
compound microscope. Compare its
structure to that of the abalone seen
in the last lab class.
Practical 7: Mollusca 2
64
Nervous system
•
Cephalopods have the most complex nervous systems among invertebrates. The
cerebral ganglia (or brain) are enclosed in a cartilaginous skull. Skin the dorsal
side of the head and dissect away the muscles covering the skull, and remove
the dorsal part of the skull to uncover the cerebral ganglia. The large optic
ganglia are connected at each side. Besides the cerebral ganglia, there are
another four pairs of ganglia making up the brain but these are fused together
as to be almost inseparable.
Find the large stellate ganglia, which are the motor centres of the mantle and
receive innervation from the brain.
Cut transversely through one of the eyes. Notice the outer transparent cornea,
the fleshy iris encircling the lens and the heavily pigmented retina.
Practical 7: Mollusca 2
OUTCOMES
1.
You will be able to point out the characteristics that make a mussel and
squid members of the Phylum Mollusca
2.
You will be able to point to the major structures of the body of the mussel
and squid and know their function.
3.
You will understand the similarities and differences in the structure and
function of the mantle cavity in the abalone, mussel and squid.
SELF ASSESSMENT EXERCISE
Draw up a table to compare and contrast the functional anatomy of the three
classes of molluscs you have dissected.
65
Practical 7: Mollusca 2
66
Practical 8: Non-segmented worms and Annelida 1
PRACTICAL 8
67
Non-segmented worms and Annelida I
MATERIAL AVAILABLE
Live animals
Nemerteans and sipunculids as available
An array of leeches, earthworms and polychaetes
Prepared slides:
Nemertea and Sipunculida – cross sections
Annelida TS, polychaete intestine
Preserved specimens:
Nemerteans, sipunculids, echiurans
AIMS
1. To illustrate the characteristics of the phyla Nemertea, Sipunculida, Echiura and Annelida
2. To illustrate the characteristics of the three main classes of the phylum Annelida: Polychaeta,
Oligochaeta, and Hirudinea; N.B. In some text books, Oligochaeta and Hirudinea are
considered sub-classes of the class Clitellata.
3. To illustrate important morphological features of some polychaetes and their use in
identification of these animals.
PREPARATORY READING
1. Read these laboratory notes.
2. Read the introductory notes on each phylum in your textbook
Practical 8: Non-segmented worms and Annelida 1
68
LABORATORY TASKS
Phylum Nemertea (sometimes called Rhynchocoela) (Ribbon worms)
Nemerteans are elongate, mostly marine worms that live in crevices or burrows from which they
actively move about. There are about 900 species.
i. Observe the living specimens of nemertean worms. Examine the head region to see
the eyes, cephalic groove or slit, mouth, proboscis pore. Watch how the animal
moves. You should be able to compare the body movements with those in
turbellarians that you have seen in a previous practical and in annelids that you see
later in this practical. What are the similarities and differences?
ii. Examine the preserved specimens of nemerteans for better views of the head region.
Dissections are necessary to reveal the separate proboscis and alimentary tract, but
these are revealed in histological sections as seen next.
iii. Examine the cross sections of nemerteans (2 slides) noting the separation between:
proboscis and alimentary tract, the layers of the body wall, nerve cords, and gonads
Compare these with the patterns in turbellarians that you have seen in a previous
practical.
Phylum Sipunculida (Peanut worms)
These marine worms burrow into tight spaces into which their stout bodies fit perfectly. The 300
species are all marine and most are a few mm long, but some are up to 1 m long.
i. Examine the living specimens of sipunculans to distinguish these features: anterior,
posterior end, trunk, anus, mid-dorsal line, introvert, hooks on introvert, nuchal
organ, tentacle, mouth. These last features will be visible when the introvert is
extended; active live specimens usually put on a good display.
ii. Examine the preserved specimens to find the features you missed on the living
specimens. Look at several different species of these preserved specimens, and
examine the internal organs of those specimens already dissected. You may wish to
carry out your own dissections to reveal the organisation of the internal organs.
Iii Examine the cross sections (or diagrams of cross sections) to appreciate the internal
structure of sipunculids. Note the large coelom, gut and muscle blocks.
Phylum Echiura (Spoon worms)
These benthic, shallow water marine, burrowing, stout worms range in size from 15 mm to 50
cm. There are about 350 species.
Practical 8: Non-segmented worms and Annelida 1
69
i. Examine the two preserved specimens but treat them with extreme care. Distinguish
the anterior (bilobed) non-retractable proboscis, mouth at the base of the proboscis,
terminal anus.
ii. If there are living specimens observe these too.
Phylum Annelida (Annulus = ring; segmented worms)
There are about 15000 species of segmented worms which include bristle worms (mostly
marine), earthworms (mostly terrestrial) and leeches (mostly marine). Some are tiny and some
reach 3m length, but most are centimeters long.
1.
Survey of the three main classes of Phylum Annelida
i. Examine the preserved and living specimens of the 3 main classes of Annelida (Oligochaeta,
Hirudinea, Polychaeta), and construct a dichotomous key to these 3 classes using characters
of external morphology: segmentation, annulation, suckers, setae, parapodia, cephalic
appendages.
ii. Using living specimens from each class, make observations of and write down notes about:
a.
b.
c.
2.
the alterations in body shape made by each specimen on surfaces, and in fluid;
points of contact between body surface and substratum;
different methods of locomotion in the same individual.
Anatomy of a typical polychaete
•
Select one of the preserved polychaetes (family Nereidae) provided for dissection and place it
under water in a dissecting tray. Distinguish the anterior (head) end, and the posterior end,
and determine the dorsal and ventral surfaces.
•
Find the mouth and the cephalic appendages dorsal to it. The prostomium is the most
anterior part of the body and is not considered to be a true segment. In the nereids it bears
two bi-articulate ventro-lateral palps, which are partially fused to it, and two prostomial
tentacles. There are two pairs of eyes just posterior to the prostomial tentacles. The
peristomium is the first true segment. It surrounds the mouth and bears peristomial tentacles
or cirri.
•
Examine the elongate segmented body. The anus opens on the terminal segment, called the
pygidium. This also bears two sensory appendages, the anal cirri. Most of the other
segments bear a pair of lateral paddle-like flaps, the parapodia. Using your scalpel or fine
scissors, remove one from the mid-body region, place it in a depression slide and examine
under higher power. Compare this to the prepared slides of parapodia.
Practical 8: Non-segmented worms and Annelida 1
70
•
The parapodia of nereids are biramous. The setae are borne on each of the bilobed
projections, the dorsal notopodium and the ventral neuropodium. Within the muscle of the
parapodia, find the black rods (or aciculae) that add support to each lobe of the parapodia.
The appearance of parapodia varies greatly among families of polychaetes.
•
Pin the animal to the dissecting tray, dorsal side up, with one pin through the peristomium
and one about half way down the body. Working forward from this pin, make a shallow cut
through the body wall, just to one side of the mid-dorsal line. Cut forward for 3-4 cm, but
stop at least 2-3 cm before the head.
•
Open the cut. To one side lies the gut which, together with the dorsal blood vessel, is in close
association with the dorsal body wall. Carefully tease the gut and blood vessel away from the
body wall and pin the flaps of the body wall open. Identify all visible structures.
•
Observe the segmental arrangement of the body cavity. Between each segment is a thin
septum, between which the gut pockets out. Each segment has a pair of nephridia on the
body floor, lateral to the gut. The base of the aciculae are visible protruding into the body
wall. Displace the gut to one side to see the ventral blood vessel and the lateral vessels
passing to the branchiae in each segment. These lateral vessels then pass dorsally to join the
dorsal blood vessel. Find the double ventral nerve cord beneath the ventral blood vessel.
Note the blocks of longitudinal muscle in the body wall.
•
Continue to cut forward to the peristomium and separate the gut from the body wall as
before. Anteriorly the gut is an expanded muscular pharynx that contains an eversible
proboscis. Slit through the roof of the pharynx to expose the black chitinous jaws. These
are exposed when the proboscis is everted and are used to catch prey.
Practical 8: Non-segmented worms and Annelida 1
71
5. Cross sections of polychaetes
Examine the microscope slides "Annelida TS polychaete" and "Polychaete intestine TS" and
determine the spatial organization of the:
i)
ii)
iii)
iv)
v)
body wall musculature (circular muscles thin, longitudinal muscles in separate bands,
oblique muscles to the bases of the acicula),
coelom (reduced by intrusion of longitudinal muscles),
intestine, and its musculature,
dorsal and ventral blood vessels,
ventral nerve cord.
OUTCOMES
1.
You will be familiar with the internal and external characteristics of annelids, nemerteans,
sipunculids and echiurans and be able to distinguish from each other.
2.
You will be able to differentiate between the three classes of annelids based on external
morphology.
3.
You will understand the internal anatomy of a polychaete and be able to identify
structures on whole or sectioned specimens.
Practical 8: Non-segmented worms and Annelida 1
72
Practicals: 9: Annelida 2
PRACTICAL 9
73
ANNELIDA 2
MATERIAL AVAILABLE
Preserved specimens:
Collections of known and unknown species from common and rare families of
polychaetes
Live material:
An array of polychaetes from as many families as possible.
AIMS
1. To give practice at using keys to the families of polychaetes; and
2. To illustrate the details of the morphological characteristics of polychaetes which are
necessary for identification of polychaetes to the family level.
PREPARATORY READING
1. Read these laboratory notes, so that you are familiar with the characteristics described in
the glossary.
2. Read the section on polychaetes in your textbook.
3. Shepherd, S. A. & Thomas, I. M. (eds.) 1982. Marine Invertebrates of Southern
Australia. Part 1. Government Printer, South Australia. Zool. 592.0994 1982 MAR,
available in the laboratory, pp. 228-292 ONLY family descriptions and glossary.
LABORATORY TASKS
Use the key to confirm the identity of several polychaetes of known families
•
Select a specimen of the family Nereidae and use the following key and glossary of the
terms used in the key to identify it.
•
Write down the choices you made at each dichotomy. This will allow you to quickly
determine where you may have gone wrong in the key. It may also be helpful to make
sketches and notes about the characters in each of these dichotomous choices.
•
Discuss with the demonstrator and your fellow students difficulties that you have with the
key. Since the key shows for each dichotomy which previous choice in the key directed
Practicals: 9: Annelida 2
74
you to the present choice, one way of resolving your problems is to trace backward
through the key for the proper choice at each dichotomy. This backwards technique is
valuable because it helps show how the author of the key interprets the characters used in
the key, and in fact, all keys take some practice in their use before anyone can use them
quickly and efficiently. You should repeat this task with several polychaetes for which
you already know the family identification, just to give you the practice with this key.
Choose from the following known families:
Nereidae
Terebellidae
Polynoidae
Eunicidae
Sabellidae
Aphroditidae
Glyceridae
Sigalionidae
Chaetopteridae
Cirratulidae
Amphinomidae
Use the key to identify polychaetes of unknown families
•
Work through several specimens of different species of polychaetes unknown to you, and
determine their family identification, using the key as before. When you have made an
identification, use the reference books provided in the lab to find a description of the
family and some diagrams of representative species, and compare these descriptions with
your worm. You may find that the family descriptions suggest some additional unique or
distinctive characters which your worm should have if your identification is correct.
•
If necessary, prepare a slide of a parapodium (or parapodia if there are more than one type
of parapodia) and prepare a slide of the setae. When both you and the demonstrator are
convinced that your specimen is identified correctly to family, you can try to identify the
specimen to genus or species using the keys in Shepherd and Thomas.
Examine the display of identified worms assembled during this practical period, and make
notes about the obvious external characters which characterize each family.
OUTCOMES
1.
You will be familiar with the key and the terminology it uses.
2.
You will be able to use the key to identify any common polychaete.
Practicals: 9: Annelida 2
75
KEY TO SOME FAMILIES OF POLYCHAETES
N.B. 1. Some families have such a wide range of characters that they appear twice in the key.
2. Page numbers refer to Shepherd, S.A. & Thomas, I.M.(eds) 1982. Marine
Invertebrates of Southern Australia Part 1. Government Printer, South Australia.
1.
Prostomium with sensory appendages; pharynx with jaws or teeth;
parapodia well developed, often compound setae
Errant polychaetes 2
-
Prostomium without sensory appendages, often bears gooved palps,
buccal cirri, or branchial crown; pharynx unarmed, parapodia
often reduced, compound setae rarely present
Sedentary polychaetes 21
2. (1) Elytra present
Elytra absent
3. (2) Compound setae present
Compound setae absent
3
5
SIGALIONIDAE (p. 237)
4
4. (3) Jaws absent; single median antenna; dorsum sometimes
covered by a felt
APHRODITIDAE (p. 233)
Jaws present; 3 antennae; dorsum not covered by
felt
POLYNOIDAE (p. 233)
5. (2) Dorsal sensory organ, the caruncle present
No caruncle present
6. (5) Prostomium with ventro-lateral palps
Prostomium without palps
7. (6) Palps bi-articulate with a stout basal joint and a small
distal one
Palps simple, sometimes cushion shaped and partially
fused prostomium
8. (7) Compound setae absent; no more than two pairs of
tentacular cirri
Compound setae present; four or more pairs of
tentacular cirri
9. (8) Jaws if present, styliform, paragnaths absent;
tentacular cirri often jointed
Two toothed jaws, horny paragnaths often present;
tentacular cirri smooth
10. (7) A barrel-shaped gizzard follows the pharynx;
jaws absent
Gizzard absent; four or more pairs of jaws
AMPHINOMIDAE (p. 237)
6
7
11
8
10
PILARGIDAE (p. 241)
9
HESIONIDAE (p. 241)
NEREIDAE (p. 243)
SYLLIDAE (p. 241)
EUNICIDAE (p. 255)
Practicals: 9: Annelida 2
11. (6) Pharynx without jaws
Pharynx with jaws
12. (11) Dorsal cirri foliaceous
Dorsal cirri long and beaded
76
12
13
PHYLLODOCIDAE (p. 239)
HESIONIDAE (p. 241)
13. (11) One pair of jaws
PILARGIDAE (Talehsapia) (p. 241)
Two or more pairs of jaws
14
14. (13) Peristome with parapodia and setae
15
Peristome without parapodia or setae
16
15. (14) Prostomium a pointed cone; body circular in section GLYCERIDAE (p. 253)
Prostomium pentagonal; body square in section
NEPHTYIDAE (p. 252)
16. (14) Maxillae consist of numerous small elements in two or
four longitudinal series
DORVILLEIDAE (p. 262)
Maxillae consist of four or five paired plates
17
17. (16) Two long slender maxillary supports plus a third median piece
Two short broad maxillary supports, no third median piece
18. (17) Antennae absent, dorsal cirri rudimentary or absent
Three antennae, dorsal cirri strap-like
18
19
ARABELLIDAE (p. 259)
LYSARETIDAE (p. 259)
19. (17) Dorsal cirri present and usually branchiae as well;
one to seven antennae
20
Dorsal cirri absent or rudimentary; antennae
usually absent
LUMBRINEREIDAE (p. 259)
20. (19) Seven antennae, the posterior five with long ringed
ceratophores
One to seven antennae without ringed ceratophores
21. (1) Body short and stout with a tuft of filamentous anal
gills
Body elongate, no anal gills
ONUPHIDAE (p. 255)
EUNICIDAE (p. 255)
STERNASPIDAE (p. 276)
22
22. (21) Head not greatly modified; prostomium usually well developed
and obvious; buccal segment sometimes with parapodia and may
bear a pair of grooved palps or a few grooved tentacles
Head modified by the development of frilly membranes,
buccal tentacles or a branchial crown around the mouth;
prostomium often reduced and indistinguishable from the
buccal segment
23
33
23. (22) Buccal segment with tentacles retractile into the
mouth
AMPHARETIDAE (p. 285)
Buccal segment with a pair of grooved palps (often
broken off); or anterior segments with several
grooved tentacles dorsally
24
Buccal segment without any food gathering appendages
28
Practicals: 9: Annelida 2
77
24. (23) Hooded hooks present in posterior segments at least,
parapodia well developed
25
Hooded hooks entirely absent, parapodia sometimes
reduced to mere ridges
26
25. (24) Head flattened and spade-shaped, palps papillose,
gills absent
MAGELONIDAE (p. 268)
Head not flattened, grooved palps, gills often
present
SPIONIDAE (p. 266)
26. (24) Long filamentous gills at least on anterior segments
parapodia reduced to ridges
CIRRATULIDAE (p. 270)
Gills not long and filamentous, parapodia well developed
27
27. (26) Both rami of anterior parapodia well developed and with
long setae
TROCHOCHAETIDAE (p. 269)
Anterior segments uniramous, with no neuropodia, setae
short, posterior segments biramous with neurosetae as
minute uncini
CHAETOPTERIDAE (p. 270)
28. (23) Dentate crested hooks present in posterior segments at least
29
Dentate crested hooks absent
31
29. (27) Dentate crested hooks with hoods, body resembling
an oligochaete
CAPITELLIDAE (p. 278)
Dentate crested hooks without hoods, body not resembling
an oligochaete
30
30. (29) Middle segments greatly elongated, never annulated
gills rare
MALDANIDAE (p. 281)
Middle segments not greatly elongated but always annulated,
gills present
ARENICOLIDAE (p. 279)
31. (28) Capillary setae crenulate
Capillary setae not crenulate
ORBINIDAE (p. 263)
32
32. (31) Prostomium a tapered cone, body fusiform often
grooved ventrally
OPHELIIDAE (p. 274)
Prostomium notched or lobed, body swollen anteriorly
but not grooved ventrally
SCALIBREGMIDAE (p. 274)
33. (22) Head with a frilled food-gathering membrane, without
tentacles, palps or pinnate radioles
Head without a frilled food-gathering membrane but has
either tentacles or palps or bipinnate radioles
34. (22) Head with stout setae
Head without stout setae
OWENIIDAE (p. 283)
34
35
37
Practicals: 9: Annelida 2
78
35. (34) Capillary setae annulated; no marked body regions,
stout setae on head usually in the form of a
cephalic cage
FLABELLIGERIDAE (p. 274)
Capillary setae not annulated, body regions well
marked, stout setae on head are paleae which form
part of an operculum
36
36. (35) Two to three rows of paleae; caudal region long and
cylindrical; tube attached
SABELLARIIDAE (p. 283)
One row of paleae; caudal region short and flattened;
tube free
PECTINARIIDAE (p. 285)
37. (34) Head with tentacles for deposit feeding, gills often present
on the first few segments
38
Head with a crown of bipinnate radioles for suspension
feeding; no gills behind the head
39
38. (37) Tentacles retractile into the mouth, either grooved or
papillose
AMPHARETIDAE (p. 285)
Tentacles not retractile into the mouth, grooved and
never papillose
TEREBELLIDAE (p. 286)
(and TRICHOBRANCHIDAE) (p. 289)
39. (37) Tube sandy or muddy; operculum never present among the
radioles
SABELLIDAE (p. 289)
Tube calcareous, stalked operculum often present among
the radioles
40
40. (39) Thorax symmetrical with 5-12 thoracic setigers
Thorax asymmetrical with 3-4 thoracic setigers (tube
small and spirally coiled)
SERPULIDAE (p. 291)
SPIRORBIDAE (p. 293)
GLOSSARY
(Figures refer to Shepherd & Thomas - see note 2 at top of page 56)
Abdomen:
Achaetous:
Aciculum setae:
Aciculum:
Annulate:
Antenna:
Apodous segment:
Avicular:
Biarticulate:
Bidentate (setae):
posterior region of the body behind the thorax and sometimes
followed by a caudal or "tail" region (Fig. 6.24C).
lacking setae.
a stout seta resembling an aciculum (Fig. 6.11C).
a stout internal chitinous rod which supports each of the parapodial
lobes (Fig. 6.5B).
having ring-like segments or bands of colour.
a sensory projection arising from anterior or dorsal surface
of the prostomium (Fig.6.6B).
lacking a parapodium.
beaked (Fig. 6.25D).
two jointed.
with two teeth (Fig. 6. 12I).
Practicals: 9: Annelida 2
Bifid:
Bifurcate (seta):
Bipinnate:
split into two.
tip with two prongs.
structure such as a feather with a main axis and two rows of
lateral branches (Fig. 6.27A).
Biramous:
with two rami.
Biramous parapodium: a parapodium with bundles of setae developed in both noto- and
neuropodium (Fig. 6.6G).
Branchiae:
gills.
Branchial crown:
a group of filaments arranged circularly and used for feeding in
sabellids and serpulids (Figs 6.26D., 6.27A).
Branchiferous:
bearing gills.
Buccal:
pertaining to the mouth (Fig. 6.26A).
Buccal tentacles or cirri: elongate or digitiform food gathering appendages either in or
around the mouth (Fig. 6.24C).
Capillary:
hair like (Fig. 6.14D).
Caruncle:
a sensory lobe extending behind the prostomium (Fig. 6.3C).
Cephalic cage:
long forwardly directed setae which encircle the mouth (Fig.
6.20A).
Cephalic rim:
a flange encircling the head (Fig. 6.22D).
Cephalic veil:
a delicate hood-like membrane in the family Pectinariidae which
separates the opercular paleae from the buccal tentacles (Fig.
6.24A).
Ceratophore:
the basal joint of an antennae (Fig. 6.11A).
Chevron:
V-shaped chitinous jaw piece at the base of the eversible pharynx
of some Glyceridae.
Cirriform:
shaped like a cirrus.
Cirrus:
a sensory appendage observed from the superior part of the
notopodium (dorsal cirrus) or the inferior part of the neuropodium
(ventral cirrus) (Fig. 6.6G).
Compound (seta):
a jointed seta (Fig. 6.6K).
Cordate:
heart-shaped.
Crenulate (seta):
with a series of small cusps (Fig. 6.2J).
Crotchet:
a long shafted seta with a hooked or curved tip.
Dentate:
toothed (Fig. 6.2K).
Digitate:
arranged like fingers.
Digitiform:
finger-shaped.
Dorsum:
the upper or dorsal side of the body.
Echinulate:
prickly like a sea urchin.
Elytron:
a dorsal scale like structure (Fig. 6.2C).
Elytrophore:
a projection above the parapodium bearing an elytron (Fig 6.2B).
Falcate:
sickle-shaped.
Falciform:
hook-shaped.
Falciger:
a compound seta with a blunt hook at its tip.
Fascicle:
a bundle (of setae).
Foliaceous:
thin, leaf-like.
Furcate:
branching as the prongs of a fork.
Fusiform:
spindle-shaped.
Geniculate:
bent like a knee.
Genital papilla:
projections below the neuropodium on which a reproductive duct
opens.
79
Practicals: 9: Annelida 2
Harpoon seta:
Hastate:
Heterogomph:
Homogomph:
Hooded seta:
Interramal:
Lamella:
Lanceolate:
Limbate (seta):
Mandibles:
Maxillae:
Nephridial papilla:
Neuropodium:
Notopodium:
Notoseta:
Nuchal caruncle:
Nuchal organ:
Nuchal papilla:
Operculum:
Ovate:
Palea:
Palps:
Papillose:
Paragnaths:
Parapodium:
Parathoracic:
Pectinate:
Pelagic:
Peristome:
Petaloid:
Pharynx:
Pinnate:
Pinnule:
Postsetal:
Presetal:
Prostomium:
Prostomial peaks:
Pygidium:
80
a stout pointed seta with recurved barbs near the apex.
shaped like a spear (Fig. 6.1C).
a compound seta with an asymmetrical joint between shaft and
blade (Fig. 6.6H).
a compound seta with a symmetrical joint between shaft and blade.
(always known as a hook): a stout, blunt or apically toothed seta
with the apex protected by a delicate chitinous gland (Fig. 6.22B).
between two rami.
a flattened or plate-like structure.
broad at the base and tapering to the tip.
a seta with a flattened margin to the blade.
ventral, chitinous plates or rods, sometimes dentate, against which
the maxillae work.
large, hook-shaped, chitinous 'jaws' found in most errant
polychaetes.
a projection on which the excretory organ opens, usually posterior
or ventral to the parapodium.
the lower or ventral part of a parapodium (Fig. 6.6G).
the upper or dorsal part of a parapodium (Fig. .6.6G).
a seta arising from the notopodium (Fig. 6.6G).
a sensory organ on the prostomium, or extending back from it in the
form of a ciliated ridge or groove (Fig. 6.16A).
a sensory organ on the prostomium or extending back from it
usually in the form of a groove or ciliated ridge.
small sensory papilla (protuberance) on the base of the prostomium.
a modified branchial filament usually calcareous or part of the
head which seals the tube when the animal retracts (Fig. 6.27C).
egg-shaped.
a broad flattened type of seta (Fig. 6.23G).
paired projections arising from the sides of the head (Fig. 6.6B).
bearing, small, soft projections.
horny or chitinous points on the pharynx of a nereid (Fig. 6.6D-F).
segmental foot-like projections bearing setae (Fig. 6.6G).
close to the thorax.
comb-like (Fig. 6.23F).
living in open waters - living in the surface waters.
segment behind the prostomium which is modified to form part of
the head and surrounds the mouth; buccal segments.
like a petal.
the posterior part of the mouth cavity leading to the oesophagus
(Fig. 6.4B).
feather-like (Fig. 6.1B).
small feather-like structure.
posterior to the seta (Fig. 6.13C).
anterior to the seta (Fig. 6.13C).
the anterior lobe in front of the mouth bearing eyes and antennae.
chitinised antero-lateral projections of the prostomium occuring in
some polynoids.
the anal segment (Fig. 6.25A).
Practicals: 9: Annelida 2
Radioles:
Ramus:
Reniform:
Scaphe:
Sessile:
Seta:
Setiger:
Setigerous lobe:
Simple seta:
Spathulate:
Spiniger:
Spinose:
Spinule:
Spinulose:
Styliform:
Tentacle:
Tentacular cirrus:
Thorax:
Trepan:
Truncate:
Torus:
Tubiculous:
Uncinigerous:
Uncinus:
Uniramous:
Verrucae:
Ventrum:
Winged capillary seta:
81
the main tentacles in the branchial crown of Sabellidae and
Serpulidae.
a branch or prong; notopodium and neuropodium which form the
two parts of a parapodium, are often referred to as the two rami.
kidney-shaped.
A flattened caudal appendage bearing the anus in Pectinaria (Fig.
6.24A).
without a stalk.
a stiff bristle-like structure.
a segment with setae.
the part of a noto- or neuropodium which bears the setae.
unjointed seta (Fig. 6.7D).
spoon-shaped (Fig. 6.18E).
a compound seta whose blade tapers to a fine point (Fig. 6.6K,L).
bearing many spines.
a small spine.
with spines (Fig. 6.15C).
bristle-shaped.
a slender outgrowth from the head.
a cirrus arising from the peristome which is elongated to act as a
sensory organ (Fig. 6.6B).
anterior region of the body (Fig. 6.27A).
a ring of small chitinous teeth at the end of the eversible pharynx of
Syllidae.
terminating abruptly.
plural tori; a ridge on a parapodium from which setae arise.
living in a tube.
bearing uncini.
a sharp, claw-like seta, may be square or oval plate with several
curved teeth or S-shaped with a single tooth and a broad base (Fig.
6.25E).
with a single lobe or prong - uniramous parapodia lack one of the
two setigerous lobes.
small, wart-like protrusions.
the lower or ventral side of the body.
a simple unjointed seta, blade with an axial rib but margins are
flattened and tapering (Fig. 6.18D).
Practicals: 9: Annelida 2
82
Practical: 10: Lophophorates
PRACTICAL 10
83
LOPHOPHORATA
MATERIAL TO BE AVAILABLE
Prepared slides:
Bryozoa: Bugula and others
Preserved specimens:
Bryozoa, Phoronida, Brachiopoda
Live material:
Representatives of all groups subject to availability
BACKGROUND INFORMATION
There are at least 14 phyla with fewer than 500 estimated species living today (Strathmann
and Slatkin 1983. Paleobiology 9, 97-106; Table 1). This practical session considers three of
these phyla with few species (Phoronida, Brachiopoda) together with an additional phylum,
the Bryozoa which is represented by more species, but is still not considered among the major
invertebrate phyla.
AIMS
1.
To illustrate, in living and preserved specimens, the morphological features which
define these three minor phyla; known as the Lophophorates
2.
To demonstrate the structure and function of the lophophore;
PREPARATORY READING
1
Read LABORATORY TASKS in this manual in conjunction with the accounts of
each phylum in your text book. Look at the figures in your textbook referring to the
cited figures so that you are familiar with the structures that you should see in the
material in the practical session.
Practical: 10: Lophophorates
84
LABORATORY TASKS
1. Lophophorate Minor Phyla
Members of these three phyla all possess a food gathering structure called a lophophore.
Read the description of the lophophore in your textbook and decide whether it is considered
homologous in the three phyla.
a.
Phylum Bryozoa
i.
Examine the prepared slide of Bugula sp. This species is an arborescent one with
zooids in a single layer.
Examine the tips of the colony to obtain a view of young zooids, and focus up and down
to work out the 3-dimensional shape of an individual zooid and draw it. Bugula lacks
an operculum, and has lightly calcified walls surrounding the frontal membrane. The
internal organs and the retracted lophophore are visible in these slides.
Examine the zooids towards the base of the colony, and repeat the exercise of drawing
the 3- dimensional shape of the zooid. These older zooids have:
distal globular protrusions called ovicells
spines on the sides of the zooid, and
avicularia, the defensive organs
ii.
Examine the prepared slides of Flustra sp., Calinicella, and Crisia acropora, to
observe some of the variations in zooid shape, and wall structure and ornamentation.
See the slide of Cristatella for a view of the lophophore. Treat these slides particularly
carefully, as they are old. Shepherd and Thomas, p. 323- can be used to classify the
specimens to order. Discuss these determinations with your demonstrator.
iii.
Next examine several examples of living bryozoans. Observe them first in a dish of
seawater with the aid of your dissecting microscope. Not all the zooids or colonies will
be alive, but careful observation should reveal some living zooids with extended
lophophores. Watch these carefully and note how particles suspended in the water
move when they get close to the lophophore. Disturb the colony with a dissecting
needle and describe the behaviour of the zooids. Make sketches of the zooids.
b.
Phylum Phoronida
i.
Examine the slides of distal fragments of small phoronids. These show the lophophore
but because the specimens are flattened, the 3-dimensional nature of the lophophore is
not evident.
ii.
Observe the living specimens of phoronids; especially look at the base of the
lophophore to detect the spiral shape of the lophophore.. Can you detect any evidence
of feeding currents?
iii.
Examine the slide of an actinotroch larva of a phoronid and list its features which
distinguish it from other larvae you have already observed.
Practical: 10: Lophophorates
c.
Phylum Brachiopoda
i.
Examine the preserved specimens of articulate brachiopods. Since most of the
specimens have been dissected each one may be incomplete.
ii.
a)
distinguish between dorsal and ventral valves,
b)
observe the 3-dimensional coiling of the lophophore;
c)
examine the positions of the muscles inserting on dorsal and ventral valves and
make sketches of these in order, in a later laboratory session, to compare these
with the adductor muscles in bivalve molluscs.
85
Examine the preserved specimens of inarticulate brachiopods (Anderson Atlas plate
76). Look at an undissected specimen but choose an already-dissected one to observe
the lophophore and muscles joining valves, as you did in the articulate brachiopod.
Make sketches of these and compare and contrast the examples of these two classes.
Unfortunately, we probably will not have any living specimens of these animals.
2. Review of “worm” and worm-like protostomes
Phylum
common name
Platyhelminthes
flat worms
Nemertea
ribbon worms
Sipunculida
peanut worms
Echiura
spoon worms
Mollusca
molluscs
Annelida
segmented worms
Phoronida
horseshoe worms
___________________________________________
Use macroscopic, external characteristics to construct a dichotomous key which would
distinguish among members of these seven phyla. Discuss your key with your fellow students
and the demonstrator.
Recognize on sight the specimens provided by your demonstrator.
SELF ASSESSMENT EXERCISE
1.
To organise the information you have just gained about the three phyla of
Lophophorates, construct a table of conspicuous, external diagnostic characters which
would allow you to identify a specimen if it belonged to one of these phyla. Discuss
the content and usefulness of this table with your demonstrator.
2.
Distinguish among a hydroid, fan worm, and bryozoan making lists of the
distinguishing features of each.
Practical: 10: Lophophorates
86
Practical 11: Blastocoelomates (Pseudocoelomates)
PRACTICAL 11
87
BLASTOCOELOMATES (PSEUDOCOELOMATES):
PHYLA: NEMATODA, ROTIFERA &
ACANTHOCEPHALA
MATERIAL AVAILABLE
Prepared slides:
Ascaris TS, slides N1, N2, N14&15, N34
Preserved specimens:
Male and female Ascaris (1 per student)
Acanthocephala
Live material:
Rotifers
AIMS
1. To illustrate the characters of three blastocoelomate (pseudocoelomate) phyla.
2. To give further practice in identification using diagnostic keys.
PREPARATORY READING
1.
2.
The account of blastoceolomates in this manual.
Brusca and Brusca pp. 334-378; 337-386.
LABORATORY TASKS
1. Nematoda
a. Between pairs of students, dissect both a male and female Ascaris by making a
longitudinal cut through the body wall along the entire length of the body. Use
any display diagrams to help you identify the following structures:
i.
alimentary canal - terminal mouth, foregut with buccal cavity and
muscular oesophagus, long dorso-ventrally flattened midgut, hind-gut and
sub-terminal anus.
ii. lateral lines - excretory tissue surrounding the longitudinal excretory
ducts.
iii. female reproductive system - two filamentous coiled ovaries surrounding
the midgut in the posterior third of the animal; continuous with similarly
coiled oviducts running backwards then turning forwards as thick eggfilled uteri; a single vagina opening at the female genital pore.
Practical 11: Blastocoelomates (Pseudocoelomates)
88
iv. male reproductive system - a single coiled testis in midgut region leading
into a similarly coiled vas deferens; a long straight seminal vesicle which
posteriorly becomes the narrower ejaculatory duct; ventral opening into
the hindgut along with two small dorsal sacs which contain the penal
setae.
b. With your dissections still in front of you, examine the cross sections of the
intestinal region of Ascaris . Refer to Brusca and Brusca, Ruppert and
Barnes, or Barnes and use your dissections to identify the following structures:
i.
The cuticle which is thick and appears structureless.
ii. The hypodermis which is an epidermal layer showing no cell walls. It
consists of a protoplasmic mass in which nuclei are scattered; this layer is
thickened mid-dorsally and mid-ventrally to enclose the nerve cords, and
mid-laterally to contain the lateral canals.
iii. The neuromuscular cells which consist of a striated basal portion attached
to the hypodermis, (the contractile portion) and an enlarged, irregular
medullary portion containing the nucleus. The medullary portion of the cell
extends far into the pseudocoelom, and there is a protoplasmic extension
linking it with the dorsal or ventral nerve cord. Note the absence of a
circular muscle layer.
iv. The pseudocoelom. This is a continuous space surrounding the alimentary
canal. It is not a true coelom (refer to phylum Annelida) but results from the
coalescence of vacuoles in large cells which lie between the neuromuscular
layer and the endodermal wall of the gut.
v. The alimentary canal. The intestinal wall is a single layer of endoderm cells
covered internally and externally by a very thin cuticle. (These sections have
been cut from the midgut region). Note the absence of muscle in the gut
wall.
vi. The nervous system consists of a pair of nerve cords, one dorsal and one
ventral.
vii. The excretory system consists of two lateral lines each containing a canal;
evidence as to how this system functions is not complete.
c. Examine the cross sections of male and female Ascaris and, using your
dissections to help you interpret the slides, identify all parts of the reproductive
systems.
d. Using the named slides work through the key at the end of this section to
familiarise yourself with the characteristic features of different nematodes.
e. Test your understanding by identifying the unknowns on slides N1, N2, N(14 &
15) and N34 to superfamily and genus. Check your identifications with the
demonstrator.
Practical 11: Blastocoelomates (Pseudocoelomates)
89
2. Rotifera and Gastrotricha
a. Make a wet preparation from the pond water provided (see Protozoa, pp.12 of
this manual, for directions if necessary), and examine under low power. The
preparation should contain rotifers and gastrotrichs plus a variety of protists
and microalgae.
i.
Rotifers can be distinguished from protistans by their larger size and the
presence of internal organs visible through the transparent cuticle. The
most common forms are oval in shape with three body regions: a flattened
"head" with a distinctive ciliary apparatus - the trochal disk or corona; the
trunk containing the internal organs; and the tail or foot with two pincer-like
toes (Brusca and Brusca, Ruppert and Barnes, Barnes).
ii. Gastrotrichs are larger and more elongate than rotifers and lack a corona.
Their cuticle is often sculptured into scales and spines and there may be a
ring of cuticular hooks around the mouth. A head region is distinguished
from the rest of the body by a slight constriction, and the body is forked
posteriorly (Brusca and Brusca, Ruppert and Barne, Barnes).
Refer to your text for complete details of rotifer and gastrotrich morphology.
You should be able to recognise the two forms and know how to distinguish
them from each other and from other microorganisms.
3. Acanthocephala
a) Examine a preserved specimen of these parasitic worms. Using Brusca and
Brusca, Ruppert and Barnes or Barnes and the display diagrams from
Bullough, identify the proboscis with its six rows of hooks for attachment,
the narrow neck and the cylindrical body terminating with the genital pore.
All of our specimens are female and most have already been slit
longitudinally somewhere along the body. Note the absence of a digestive
tract, the large retractor muscles of the proboscis, the ovarian tissue and
free eggs, and the ovarian funnel, uterus and vagina.
SELF ASSESSMENT EXERCISE
Tabulate the members classified as blastocoelomates, and in that table compare
and contrast the main, body structural details.
Practical 11: Blastocoelomates (Pseudocoelomates)
OUTCOMES
1.
You will be able to recognize the internal body structures of both male and
female nematodes.
2.
You will be familiar with the key to the nematodes and understand the
terminology it uses and so be able to identify the nematodes on prepared
slides to genus.
3.
You will be able to consider the relationships between these four phyla,
based on shared characteristics and unique features.
90
Practical 12: Arthropoda Introduction: Chelicerata, Myriapoda
PRACTICAL 12
91
PHYLUM ARTHROPODA
MATERIAL AVAILABLE
Prepared slides:
An array of slide material representing arthropod diversity
Preserved material:
An array of whole specimens representing arthropod diversity
AIM:
To introduce you to the morphological diversity of members of the phylum Arthropoda
PRELIMINARY READING
Brusca and Brusca 2003, pp. 461 - 506; pp. 461 - 489.
Ruppert and Barnes, pp. 596 - 616
Moore, Chapters 12 – 15.
INTRODUCTION:
The Arthropoda is the most speciose phylum, with >1,000,000 species described. You
may have swum with the first arthropods – if you were alive and swimming at the time
–in the early Precambrian seas and clearly their bauplan is successful because they
have radiated and now occupy practically all environments on Earth. One of the stem
stock were the crustaceans, now predominantly (but not exclusively) aquatic from
which the now predominantly (but not exclusively) terrestrial insects have evolved.
Two other clades we will spend some time reviewing are the myriapods, and the
cheliceriformes. We devote two practicals each to the crustaceans and the insects,
arthopods of great diversity and sometimes of great commercial importance, but we
begin with a general introduction to arthropod diversity (What is an arthropod?) and
have a brief encounter with the cheliceriformes and the myriapods.
OUTCOMES
1. You should be able to recognise an arthropod, with reasons.
2. You should be able to recognise the major arthropod sub-groups (Sub phyla), with
reasons.
Practical 12: Arthropoda Introduction: Chelicerata, Myriapoda
LABORATORY TASKS
What is an arthropod?
Working in small groups, divide the material available in the laboratory into groups,
and be prepared to justify your groupings.
Do this exercise BEFORE you delve into the text books in the practical class.
Summarise the results of your group’s and classes deliberations:
92
Practical 12: Arthropoda Introduction: Chelicerata, Myriapoda
93
SUBPHYLUM CHELICERIFORMES
The subphylum comprises two classes, the Class Pycnogonida (fascinating, beautiful
creatures also known as sea spiders) and the Class CHELICERATA (with two
subclasses, Merostomata (horseshoe crabs) and Arachnida (spiders, scorpions, ticks,
for example).
AIM:
To understand the basic external structure of Chelicerata and how chelicerates differ
from other arthropods. Specimens of Limulus, scorpions, pseudoscorpions, opiliones, ticks,
spiders are available in the laboratory: work in pairs.
SUBCLASS MEROSTOMATA
This group of marine organisms comprises the Eurypterida and Xiphosurida. Both
groups were present in Cambrian times and were companions of the Trilobita. Today,
the Eurypterida, known only as fossils, are notable among the Arthropoda because
some of them attained such a large size, up to 2 metres in length. Their greatest
development was during the Silurian and Devonian periods.
The Xiphosura, well represented as fossils during the Palaeozoic, has present day
living species grouped in 3 genera. Examine preserved specimens of Limulus
comparing them with textbook diagrams. This animal, in its present form, dates from
the Jurassic times in the Mesozoic era.
Limulus (horseshoe crab)
General anatomy: segments of prosoma covered by carapace; tergites of mesosoma
fused into shield; telson. Pair of median ocelli and pair lateral 'compound' eyes on
carapace. Mouth ventral.
Prosoma, appendages:
1.
Chelicerae, each with 3 articles, chelate.
2.
Pedipalps chelate in female, subchelate in male.
3, 4, 5.
Chelate.
6.
With terminal movable spines, used for shovelling sand.
2-6.
Have masticatory spines on gnathobases.
7.
Chilaria, pair pre-genital appendages.
Opisthosoma, appendages:
1.
Genital operculum, genital ducts open behind.
2-6.
Paired branchial appendages, 150-200 leaf-like gills behind each
'exopodite'.
7&8
lacking appendages.
Telson, spine-like.
Locomotion is by flapping of opisthosomal appendages or levering with tail spine.
Distribution: Oriental coasts, North America.
Practical 12: Arthropoda Introduction: Chelicerata, Myriapoda
94
SUBCLASS ARACHNIDA
There are eleven Orders comprising the Arachnida. For the 5 most common Orders the Scorpionida, Pseudoscorpionida, Opiliones, Acarina and Araneae, live and
preserved material is available. Examine the specimens, focussing on the Araneae
(spiders) and Scorpionida) provided and make sure you understand why these animals
are cheliceriformes.
SUBPHYLUM MYRIAPODA
AIM
To understand the basic external structure of myriapods and how they differ from
other arthropods.
Preserved specimens of millipedes and centipedes are available for study in the laboratory.
Usually with numerous post-cephalic body segments
Body with head plus trunk
Mandible with articulating endite
Coxae with single articulation with the sternum.
There are four subclasses, but members of only two are commonly encountered,
millipedes (Subclass Diplopoda) and centipedes (Subclass Chilopoda).
OUTCOMES:
You should be able:
1.
to recognise a member of the subphylum Cheliceriformes, with reasons;
2.
to recognize a member of the subphylum Myriapoda, with reasons; and
3.
demonstrate an understanding of the diversity within both classes
SELF ASSESSMENT
An array of chelicerates and myriapods will be available in the laboratory. You should
be able to classify each sample into its subphylum, with reasons.
Practical 13: Crustacea 1
95
PRACTICAL 13
SUBPHYLUM CRUSTACEA 1
MATERIALS AVAILABLE:
Preserved specimens:
Stomatopoda, Brachyura, Isopoda, Amphipoda
Material for dissection:
Cherax – one per student
Crab – one per stud
AIM:
To understand the external morphology of a crustacean, as exemplified by two
members of the Order Decapoda, Class Malacostraca.
PREPARATORY READING:
Brusca and Brusca
Ruppert et al.
Moore
pp. 595-661 or 511-587
pp. 606 - 695
pp. 168 - 180
INTRODUCTION
Crustaceans are an ancient group of mandibulate, predominantly aquatic
arthropods. The first crustaceans are presumed to have possessed a head with 5
pairs of appendages and a long trunk with paired, jointed appendages on each body
segment. Given their long history (phyllocarid crustaceans date from the midCambrian) and ability to exploit a wide variety of habitats, it is not surprising to
find considerable morphological diversity within the Crustacea. Consequently, it is
difficult to define the taxon in terms of unique features shown by all members, but
there are two features typically considered diagnostic of Crustacea.
• two pairs of (pre-oral?) antennae and
• biramous, jointed appendages.
In addition, it is only in some forms that you will find a nauplius larva.
Given the extreme morphological diversity in body plans shown by crustaceans, the
two lectures and two practical classes will concentrate on introducing you to the
basic body plan and associated vocabulary. Armed with that background, you
should be able to apply the knowledge and logic to sorting out the identity of any
crustacean so long as you a text in hand, as well.
LABORATORY TASKS
1. Examine the externals of the crayfish (Malacostraca : Decapoda).
The animal apparently has but two tagmata, cephalothorax plus abdomen, for the
head and thorax appear fused.
Practical 13: Crustacea 1
96
a. Cephalothorax
i.
Identify the carapace, an expansion of the posterior epimeres of the head,
and enclosing, laterally, respiratory chambers. The carapace has ridges and
spines, and is extended medially into a rostrum. The ridges, spines and
rostral armature frequently are used in decapod taxonomy. Identify those
present on your specimen.
ii. Identify the stalked compound eyes; 2 pairs of antennae; mouthparts; and 5
pairs of ambulatory appendages.
b. Abdomen
i. Identify the telson, pleopods and uropods.
ii. The arrangement of tergites and sternites is clearly seen on the pleomeres.
Locate the epimeres. These are sometimes erroneously called pleura; what
are pleura in arthropods?
c. Limbs
Limb structure is important in crustacean classification. Processes on the inner
margins are called endites; those on the outer margins are called exites. Endites
used for manipulating food (often at the proximal end of an appendage) are
called gnathobases.
i. On the cephalothorax, dissect the appendages from one side of the specimen,
beginning with thoracopod number 8 (the posterior-most walking leg) and
finishing with the 1st antenna. Keep the limbs in order on damp paper
towelling.
ii. The ambulatory appendages of the crayfish are stenopodial limbs. Note:
their structure, including number and shape of segments; presence of
endites and exites; and consistency in these respects between all ambulatory
appendages of the crayfish. Draw one thoracopod and name the various
parts.
Compare the gross structure of the last 5 thoracopods of the crayfish with
the corresponding limbs of the syncarid Anaspides tasmaniae. What is the
obvious difference? What might be the functional significance of this
difference?
iii. Now study and draw the remaining limbs you have dissected from the
crayfish. What might their function be in each case? Explain.
iv. Note the structure of the pleopods. Is there any evidence of sexual
dimorphism? (You will need to compare your specimen with others in the
class).
What method of locomotion is suggested by the pleopods? Check by
watching locomotion of the live crayfish.
d. Telson
Describe the tail fan. Of how many parts is the fan formed? Where is the anus?
What functions does the tail fan have?
Practical 13: Crustacea 1
97
EXTERNAL ANATOMY OF THE CRAYFISH
Practical 13: Crustacea 1
Order: Stomatopoda
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
98
Practical 13: Crustacea 1
Order: Isopoda
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
99
Practical 13: Crustacea 1
Order: Amphipoda
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
100
Practical 14: Crustacea 2
101
PRACTICAL 14
SUBPHYLUM CRUSTACEA 2
MATERIALS AVAILABLE:
Preserved specimens:
Thoracica, Conchostraca, Anostraca, Notostraca
AIM:
1.
To exemplify and learn how to distinguish the following taxa.
Classes
Sub classes
Branchiopoda
Maxillopoda
Orders
Notostraca
Conchostraca
Cladocera
Anostraca
Ostracoda
Copepoda
Cirripedia
Thoracica
PREPARATORY READING:
Brusca and Brusca pp. 595-661 or 511-587
LABORATORY TASKS
1. Learn how to distinguish the body plans of the taxa listed above.
2. Recognise the major diagnostic features of each taxon and mark them on the
following diagrams, making notes and comments where appropriate.
OUTCOMES
By the time you have completed your practical studies on crustaceans, you should
be able to:
1) Recognize a crustacean, with reasons;
2) Name the macroscopic body structures of crustaceans
3) Describe the pattern of tagmosis in crustaceans
4) Describe the limb structure of crustaceans.
Practical 14: Crustacea 2
Order: Anostraca
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
102
Practical 14: Crustacea 2
Order: Notostraca
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
103
Practical 14: Crustacea 2
Order: Conchostraca
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
104
Practical 14: Crustacea 2
Order: Cladocera
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
105
Practical 14: Crustacea 2
Subclass: Ostracoda
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
106
Practical 14: Crustacea 2
Subclass: Copepoda
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
107
Practical 14: Crustacea 2
Order: Thoracica
State the higher classification of this order.
What morphological features, useful for identification, about this taxon are
noteworthy?
List the habitats for members of this taxon.
108
Practical 15: Insect dissection
PRACTICAL 15
109
SUBPHYLUM HEXAPODA: INSECT DISSECTION
MATERIAL AVAILABLE
Fresh material:
Cockroaches
AIMS
1.
2.
3.
To familiarise you with the internal anatomy of insects;
Understand how insects breath, ingest and process food and remove
nitrogenous waste material; and
Understand the basic anatomy of the reproductive system of insects.
DISSECTION OF THE COCKROACH
In this practical session we will be dissecting a cockroach to learn more about the
external and internal structures of an insect. The cockroach represents the general
insect form. There is significant variation in the external and internal structures of
each species as they are adapted for different niches.
Procedure: Set up a wax dissecting dish with pins ready for the locust or
cockroach.
1. Look at the Cockroach Body
a. Determine the location of the three main body segments: head,
thorax, and abdomen.
b. Note where the legs and wings attach. How many pairs of wings are
there and what is their general shape and relative size.
c. What type of antennae do cockroaches have?
d. What type of mouthparts do cockroaches have?
e. What leg types do cockroaches have?
f. How does the exoskeleton of the cockroach feel? What is the
outermost layer of the cockroach? What purpose does it serve?
2. Remove the legs and wings by cutting at their bases hold the insect dorsal
side towards you - you will dissect from the DORSAL surface. By the way its
useful to sex the insect before you dissect it.
3. Draw and label the structures of the hind leg.
a. How many tarsal segments does a cockroach have?
4. Lay the cockroach ventral (belly) side down on the dissecting dish. Pin the
body to the dish by inserting a dissecting pin through the anterior end (head)
and a second one at the posterior end of the body. Gently stretch the body
before securing the posterior pin.
Practical 15: Insect dissection
110
5. With fine scissors, gently begin to cut the exoskeleton along the lateral lines
between the notum and the pleuron of the abdomen on both sides of the
abdomen from the posterior end of the body to where the pronotum ends. As
you cut ensure that the points of the scissors are outward. With a pair of
forceps gently fold up the dorsal section of the exoskeleton and cut across
the top so that the flap of exoskeleton (the notum) can be removed.
6. Pin this cut section and examine the heart. You should see the heart
surrounded by its pericardial cells. Make sure that the remainder of the
internal parts falls back within the body cavity. Cut the notum as far as you
can over the last one or two segments.
7. Cover the body with water
8. The trachea. The most obvious feature of the opened insect is the profusion
of trachea and yellow-white fat bodies. Examine these trachea under the
binocular tracing the main branches to the spiracles.
9. Gently remove the excess fat body from the abdomen using a pair of forceps.
10. The reproductive system. At the posterior end of the insect, lying within
this tangle of tubes and fat, are the ovaries and testes. Separate these out
carefully from the fat and trachea noting the oviducts and vas deferens
leading around the gut to the accessory glands and their genital openings
on the ventral surface.
11. The gut. Leave the gonads intact and displace the gut to one side and pin it
in this position. Remove the fat and trachea so disclosing the gut. Make
sure that you open the thorax completely to reveal the foregut. Displace the
gut to one side with a pin, as shown in the diagram below. Ensure that you
disentangle the trachea and fat. You will notice, at the junction of the
midgut with the hindgut, that there are numerous fine pale-coloured tubes.
These are the Malpighian tubules used in excretion and water balance.
Trace the gut forward to the midgut diverticula or gastric caeca. Before
these are the crop and oesophagus providing the foregut. The small
muscular mass anterior to the connection between mid and foregut is the
proventriculus - a remarkable structure in the cockroach. The rectum,
leading from a short hindgut, is bulbous and clearly striped. These stripes
are the outlines of the rectal pads employed in water retention.
12. Display gut to one side and draw.
13. Dissect the proventriculus from the rest of the digestive tract. Cut it in half
longitudinally and look at it under the microscope. What do you observe?
Practical 15: Insect dissection
DISSECTION OF THE FEMALE COCKROACH
111
Practical 15: Insect dissection
112
14. Gonads and accessory glands. With the gonads and gut displaced you
should have access to the accessory glands. These are more pronounced in
the male than the female. There is a complex of glands over the male
ejaculatory duct including the white, hyaline and opalescent glands and
the seminal vesicle. They form a tightly wound mass of tubes. In the
female, the most obvious structure is the spermatheca. In the cockroach
the male has a large white mushroom gland beneath the gut - these are the
male's accessory glands. In the female the 8 ovarioles open to the common
oviduct after the 6th segment.
15. The nervous system. Now remove the gut and the gonads carefully.
Remove all traces of fat and take care with the remaining trachea. The large
ganglia of the thorax will be easy to locate - in the locust the pro- and
mesothorax each have distinct bilobed ganglia, whereas in the locust
metathorax the ganglia coalesce to form a compound ganglion of the thorax
and abdominal segments. In the cockroach it is distinct from the abdominal
ganglia. Within the rest of the abdomen the paired ganglia are clearly visible.
16. Remove the head and dissect the mouthparts from the head.
17. Lay out the separate mouthparts: labrum, mandibles, maxillae, labium.
Which ones have palps? Which are paired? Which are unpaired?
18. Clean up your dissection.
Practical 15: Insect dissection
DISSECTION OF THE FEMALE COCKROACH (AGAIN)
113
Practical 15: Insect dissection
114
OBJECTIVES AND SELF TEST
1.
2.
3.
4.
5.
Understand the basic layout of the internal organs of the insect.
List the parts of the gut. What is the role of the proventriculus in the
cockroach?
Note the Malpighian tubules and the organisation of the rectal pads - why
should you consider these two structures together?
What is the organisation of the gonads - what is the function of the accessory
glands in both sexes and what is the function of the spermatheca in the
female?
What is the function of the ganglia?
Outcomes
You should be able to:
1) Describe the external and internal anatomy of an insect
2) Describe how the digestive, respiratory, excretory and reproductive systems
of insects are structured and function.
Practical 16: Systematic Entomology
PRACTICAL 16
115
SYSTEMATIC ENTOMOLOGY
MATERIAL AVAILABLE
Prepared slides:
Collembola, Thysanura, Siphonaptera, Phthiraptera
Preserved material:
Boxes or wet specimens of selected insects illustrating all major orders:
Thysanura, Odonata, Blattodea, Isoptera, Mantodea, Dermaptera, Orthoptera,
Phasmatodea, Hemiptera (Heteroptera, Homoptera), Thysanoptera, Neuroptera,
Coleoptera, Diptera, Lepidoptera, Hymenoptera
AIM:
To understand their systematic relationship to order level by keying out adult insects
and the main reasons underlying their diagnostic characters.
INTRODUCTION:
All six-legged creatures are members of the Hexapoda but not all are insects! Four
classes have been created which acknowledge the polyphyletic nature of this
assemblage. The Collembola, Protura and Diplura stand alone from the only other
true apterygote order, the Thysanura, as entognathous hexapods. The Thysanura
form the first of the insectan orders.
Although the fundamental systematic structure of the Hexapoda has been well
established you will find varying detailed approaches in different texts which express
alternative arrangements of Order and sub-Order levels. The style adopted is for the
CSIRO Textbook of Entomology - The Insects of Australia.
Practical 16: Systematic Entomology
116
LIST OF ALL INSECT ORDERS
* INDICATES THOSE NOT FOUND IN AUSTRALIA
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Archeognatha (Microcoryphia)
Thysanura (Zygentoma)o
Ephemeroptera
Odonata
Plecoptera
Blattodea
Isoptera
Mantodea
Mantophasmatodea*
Grylloblattodea*
Dermaptera
Orthoptera
Phasmatodea
Embioptera
Zoraptera*
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Psocoptera
Phthiraptera
Hemiptera (Heteroptera & Homoptera)
Thysanoptera
Megaloptera
Raphidioptera*
Neuroptera
Coleoptera
Stresiptera
Mecoptera
Siphonaptera
Diptera
Trichoptera
Lepidoptera
Hymenoptera
HEXAPOD PHYLOGENY: HEXAPODA
A. ENTOGNATHA (sometimes divided into two classes ELLIPLURA AND DIPLURA
• Protura
• Collembola
• Diplura
B. ECTOGNATHA (INSECTA)
1. APTERYGOTA
a. AMETABOLA
• Archeognatha (Microcoryphia)
• Thysanura (Zygentoma)
2. PTERYGOTA
b. HEMIMETABOLA
i. PALEOPTERA
• Ephemeroptera
• Odonata
ii. NEOPTERA
Plecoptera
Blattodea
Isoptera
Mantodea
Mantophasmatodea
Grylloblattodea
Dermapters
Orthoptera
Phasmatodea
Embioptera
Zoraptera
Psocoptera
Phthiraptera
Hemiptera (Heteroptera &
Homoptera)
Thysanoptera
Practical 16: Systematic Entomology
117
c. HOLOMETABOLA
Megaloptera
Raphidioptera
Neuroptera
Coleoptera
Strepsiptera
Mecoptera
Siphonaptera
Diptera
Trichoptera
Lepidoptera
Hymenoptera
LABORATORY TASKS
Identify as many insects as possible, using the key provided.
Keys are arranged in couplets. The couplets provide a choice between contrasting
characters. You take the route as directed at the right until you come to a name.
There is no such thing as a perfect key. If you get stuck, go back and start again,
trying another route through the key. Please ask for help if you get completely
confused. Reference and textbooks contain many illustrations and will be useful to
you.
EXPECTATIONS
1. You should be familiar with the key and the terminology used to describe insects.
2. You should be able to recognise the designated orders of insects on sight, and know
their main distinguishing characteristics
3. On the basis of common characteristics, be able to rationalise the phylogenetic
groupings of Hexapods as outlined below.
The following orders of insects should be familiar to you. Make sure that you see at
least one example of each during this practical and put common names to each of the
orders listed below:
Practical 16: Systematic Entomology
118
A check list for the lab!
Division
Apterygota
Paeleoptera
Order
Thysanura
Odonata
Checked
Common Name
Ephemeroptera
Neoptera Hemimetaboly
Blattodea
Isoptera
Mantodea
Dermaptera
Orthoptera
Phasmatodea
Phthiraptera
Hemiptera Homoptera
Hemiptera Heteroptera
Neoptera - Holometaboly
Thysanoptera
Neuroptera
Coleoptera
Siphonaptera
Diptera
Lepidoptera
Hymenoptera
This is a long but incomplete list (the full list is above). You will only become familiar
with it by recalling the associations within the phylogeny. Consult the entomology text
and note the ordering of insects.
Finally there are three non-insectan orders of which the most important is the
Collembola. Collembolans are important soil organisms.
Practical 16: Systematic Entomology
119
KEY TO THE ORDERS OF THE SUPERCLASS HEXAPODA
(LARVAE & ADULTS)
The HEXAPODA includes:
1.
2.
Class & Order
Class & Order
Class & Order
Class
COLLEMBOLA
PROTURA
DIPLURA
INSECTA
(a)
Wings present
(b)
Wingless or with vestigial or rudimentary wings
(Nymphs, larvae and some adults)
(a)
(b)
Wings membranous, not hardened or leathery
Front wings hardened or leathery, at least at the base, hind wings
if present are membranous
3.
(a)
(b)
With only one pair of wings
With two pairs of wings
4.
(a)
Grasshopper-like insect with prothoracic shield extending to a
point beyond the abdomen, rudimentary forewings when present
scale-like (grouse locusts)
2
28
3
9
4
16
Orthoptera
(b)
Not as above
5.
(a)
(b)
Wings net-veined (some mayflies)
Wings not net-veined
6.
(a)
Mouthparts beaklike, haustellate, caudal filaments usually present,
minute and delicate insects (mealy bugs and scales)
Hemiptera: Homoptera
(b)
Mouthparts mandibulate or at least not projected to form a long
sucking tube, Caudal filaments absent
(a)
Antennae with at least one segment with a long lateral process,
front wings minute, hind wings fan-like (parasitic streps)
(b)
Not fitting the above description
(a)
Tarsi nearly always 5-segmented, hind wings reduced to halteres
(flies and mosquitoes)
7.
8.
5
Ephemeroptera
6
7
Strepsiptera
8
Diptera
(b)
Tarsi 2-3 segmented, wings membranous, no halteres
(psocids and booklice)
9.
(a)
(b)
Mouthparts haustellate, elongated and often segmented
Mouthparts mandibulate or adapted for sucking and licking
10.
(a)
Beak arising from front of head, forewings usually thickened at base,
membranous at tips, overlapping when at rest
(true bugs)
Hemiptera: Heteroptera
(b
Beak arising from hind parts of the head almost at the base
of the forelegs, wings usually held tent-like when at rest
(hoppers and psyllids)
Hemiptera: Homoptera
Psocoptera
10
11
Practical 16: Systematic Entomology
11.
12.
13.
(a)
Abdomen with forceps-like cerci, frontwings usually short,
tarsi 3 segmented (earwigs)
(b)
Abdomen without forceps-like cerci, frontwings may cover the
Abdomen, or if short and obviously vestigial then hind wings
not used in flight
16.
17.
(b)
Frontwings with veins, usually tentlike or overlapping when at rest,
antennae with more than 12 segments, hindwings usually broad and
larger than the forewings
13
Body dorsoventrally flattened, head partially or completely concealed
from above by the pronotum (roaches)
Body not dorsoventrally flattened, head usually visible from above
Blattodea
14
Forelegs with strongly recurved tibia, eyes well separated
(praying mantis)
Not as above
Mantodea
15
(a)
(a)
(a)
Pronotum without large descending lateral lobes, wing rudiments
of nymphs not reversing their orientation in later instars, specialised
auditory organs absent (stick insects)
Phasmatodea
(b)
Pronotum with large descending lateral lobes, wing rudiments of
nymphs reversing their orientation in later instars, auditory organs
present either on the 1st segment of the abdomen or on the foretibia
(crickets, bush crickets and grasshoppers)
(a)
Lepidoptera
Wings transparent or covered with fine hair, mouthparts not
as a coiled tube
(a)
Wings fringed with long hairs, tiny insects, 5 mm or less in length,
tarsi 1-2 segmented (thrips)
Thysanoptera
Not as above
18
(a)
(b
19.
Wings covered or partially covered with microscopic scales,
mouthparts usually formed as a coiled tube, antennae with
many segments (butterflies and moths)
Orthoptera
(b)
(b)
18.
12
Frontwings without veins, usually meeting in the midline as hardened
wing covers (elytra), antennae with 11 or fewer segments, hindwings
if visible longer than the forewings and folded. (Do not raise the elytra
of mounted specimens to examine the hindwings) (beetles)
Coleoptera
(b)
15.
Dermaptera
(a)
(b)
14.
120
(a)
(b)
17
Mouthparts haustellate, arising from the rear of the head,
wings tent-like over the abdomen when at rest
(aphids and plant bugs)
Hemiptera: Homoptera
)Mouthparts not haustellate, wings not forming a distinct tent
over the abdomen
19
Frontwings larger than hind wings
Frontwings smaller than hindwings or nearly equal
20
24
Practical 16: Systematic Entomology
20.
(a)
(b)
21.
22.
23.
Ephemeroptera
21
(a)
Wings plainly hairy, mouthparts usually reduced, antennae as long
or longer than the body (caddisflies)
(b)
Frontwings not hairy, mandibles well developed, antennae
shorter than the body
Trichoptera
22
(a)
Forewings distinctly larger than the hindwings, mandibulate or sucking,
abdomen often but not always with a distinct constriction before the thorax
(ants, bees and wasps)
Hymenoptera
(b)
Hindwings about the same size as the forewings, soft bodied insects
without a distinct constriction between abdomen and thorax
(a)
(b
24.
Wings net-veined, abdomen with long caudal appendages
(mayflies)
Wings not net-veined and abdominal caudal appendages absent
121
(a)
(b)
Front edge (costal margin) of forewing with numerous ladder-like
cross veins, mouth not formed into a distinct beak
(antlions and lacewings)
23
Neuroptera
)Costal margin of forewing without ladder-like cross veins,
mouthparts produced into a distinct beak
(scorpion or hanging flies)
Mecoptera
Tarsi 3-4 segmented
Tarsi 5 segmented, or if 3 then basal segment of front tarsi
enlarged for web-spinning
25
27
25.
(a)
(b)
Antennae bristle-like (damsel and dragon flies)
Antennae long and slender
26.
(a
)Front wings smaller than hind wings, anal area of hind wing
usually enlarged, tarsi 3 or fewer segmented (stoneflies)
Plecoptera
Front wings nearly the same size as the rear wings, anal area
of hind wings not enlarged, tarsi 4 segmented (termites)
Isoptera
(b)
27.
28.
29.
Odonata
26
(a)
Tarsi 5 segmented, wings with ladder-like venation on costal margin
(antlions and lacewings)
Neuroptera
(b)
Tarsi 3 segmented with front tarsi enlarged for web-spinning,
wing venation simple(web-spinners)
Embioptera
(a
)Body insect-like, with segmented legs and antennae usually present
(adults, nymphs and some larvae)
29
(b)
Body more-or-less worm-like, body regions, except the head
not clearly defined (larvae and some adults)
74
(a)
Frontwings present but rudimentary, hindwings absent or as halteres,
tarsi 5 segmented (flies)
(b)
Wings entirely absent, or if present the 4 rudimentary wings,
no halteres, tarsi variable
Diptera
30
Practical 16: Systematic Entomology
30.
(a)
(b)
31.
(a)
(b)
32.
(a)
(b)
33.
(a)
(b)
34.
(a)
(b)
35.
122
Antennae absent length 1.5mm or less; usually occurring in
soil or leaf litter (proturans)
Antennae usually present (sometimes small); size and habitat variable
Protura
31
Ectoparasites of birds, mammals, or honey bees and usually found
on the host; body more or less leathery and usually flattened
dorsoventrally or laterally
Free living (not ectoparasitic), terrestrial or aquatic
32
36
Tarsi 5-segmented; antennae short and usually concealed in
grooves on head, mouthparts haustellate
Tarsi with fewer than 5 segments; antennae and mouthparts variable
33
34
Body flattened laterally; usually-jumping insects, with relatively long legs
(fleas)
Siphonaptera
Body flattened dorsoventrally; not jumping insects, legs usually short
(louse flies, bat flies, and bee lice)
Diptera
Antennae distinctly longer than head; tarsi 3-segmented
(bed bugs and bat bugs)
Antennae not longer than head; tarsi 1–segmented (lice)
Hempitera
35
(a)
Head as wide as or wider than prothorax; mouthparts mandibulate,
parasites of birds (with 2 tarsal claws) and mammals
(with 1 small tarsal claw)(chewing lice)
Phthiraptera-Mallophaga
(b)
Head usually narrower than prothorax; mouthparts haustellate;
Parasites of mammals with 1 large tarsal claw
(sucking lice)
Phthiraptera-Anoplura
36.
(a)
(b)
Mouthparts haustellate, with a conical or elongate beak enclosing stylets
Mouthparts mandibulate (sometimes concealed in head), not beak-like
37
41
37.
(a)
(b)
Tarsi 5-segmented; maxillary or labial palps present
Tarsi with 4 or fewer segments, palps small or absent
38
39
38.
(a)
Body covered with scales; beak usually in the form of a coiled tube,
antennae long and many-segmented (wingless moths)
Lepidoptera
(b
)Body not covered with scales; beak not coiled; antennae variable,
but often short, with 3 or fewer segments
Wingless flies
(a)
Mouthparts in the form of a cone located basally on ventral side of the
head; palps present but short; body elongate, usually less than 5 mm in
length, antennae about as long as head and prothorax combined, not
bristlelike, and 4-to-9-segmented; tarsi 1-or-2-segmented,
often without claws (thrips)
Thysanoptera
(b)
Mouthparts in the form of an elongate segmented beak, palps absent,
other characters variable
39.
40.
(a)
40
Beak arising from front part of head; antennae 4-or-5-segmented and not
bristlelike; tarsi usually 3-segmented; abdomen without cornicles
(bugs)
Hemiptera
Practical 16: Systematic Entomology
123
40.
(b)
Beak arising from rear of head; antennae either with more than 5 segments
(and tarsi 2-segmented) or bristlelike (and tarsi 3-segmented); abdomen
often with a pair of cornicles
(aphids, hoppers, and others, adults and nymphs
Homoptera
41.
(a)
Abdomen distinctly constricted at base; antennae often elbowed,
tarsi 5-segmented; hard-bodied, antlike insects.
(ants and wingless wasps)
Hymenoptera
Abdomen not particularly constricted at base; antennae not elbowed,
tarsi variable
42
(b)
42.
(a)
(b)
43.
Abdomen with 3 long threadlike caudal filaments and with style-like
appendages on some abdominal segments; mouthparts mandibulate,
but often more or less retracted into head, body nearly always covered
with scales; terrestrial (bristletails)
Abdomen with only 2 threadlike caudal filaments or none; if with 3
(mayfly nymphs), then aquatic; other characters variable
43
44
(a)
Compound eyes large and usually contagious; body somewhat cylindrical,
with thorax arched; ocelli present; middle and hind coxae nearly always
with styli; abdominal styli on segments 2-9
Archaeognatha
(b)
Compound eyes small and widely separated or absent; body somewhat
flattened dorsoventrally, thorax not arched, ocelli present or absent, middle
and hind coxae without styli; abdominal segments 1-6 (and sometimes 7)
without styli
Thysanura
44.
(a)
(b)
Aquatic, often with tracheal gills
Terrestrial, without tracheal gills
45
52
45.
(a)
(b)
Nymphs: compound eyes and usually wings pads present
Larvae: compound eyes and wing pads absent
46
48
46.
(a)
Labium prehensile, folded under head at rest, and when extended much longer
than head (dragonfly and damselfly nymphs)
)Odonata
Labium normal, not as above
47
(b)
47.
48.
(a)
With 3 caudal filaments: tarsi with 1 claw; gills located on lateral margins
of abdominal terga and usually leaflike or platelike
(mayfly nymphs)
Ephemeroptera
(b)
With 2 caudal filaments; tarsi with 2 claws; gills more or less finger like
(rarely absent) usually located on underside of thorax
(stonefly nymphs)
Plecoptera
(a)
With 5 pairs of prolegs on ventral side of abdominal segments,
the prolegs with tiny hooks (crotchets) (aquatic caterpillars)
Abdominal segments without prolegs or with a terminal pair only
(b)
49.
(a)
(b)
Lepidoptera
49
Mouthparts consisting of 2 slender and elongate structures, longer than head,
antennae long and slender, at least one-third as long as body, tarsi with 1 claw;
living in freshwater sponges (larvae of Sisyridae)
Neuroptera
Mouthparts, and usually also antennae, short, not as above
50
Practical 16: Systematic Entomology
50.
(a)
(b)
51.
52.
53.
54.
Tarsi with 2 claws; abdomen with long slender lateral processes and
a long slender terminal process (Sialidae) or with slender lateral
processes and a pair of hooklike structures apically (Corydalidae)
(fishfly and alderfly larvae)
Neuroptera
Tarsi with 1 or 2 claws; if with 2, then abdomen not as above
51
(a)
Abdomen with a pair of hooks, usually on anal prolegs, at posterior end and
without long lateral processes (but sometimes with fingerlike gills); tarsi with
1 claw, usually living in cases (caddisfly larvae)
Trichoptera
(b)
Abdomen with 4 hooks at posterior end or none; and with or without long
lateral processes; tarsi with 1 or 2 claws; not living in cases
(beetle larvae)
Coleoptera
(a)
Mouthparts usually withdrawn into head and not apparent; abdomen with
style-like appendages on some segments or with a forked appendage near end
of abdomen; usually less than 7mm in length
53
(b)
Mouthparts usually distinct, mandibulate or haustellate; abdomen without
appendages such as described above, size variable
(a)
Antennae long and many-segmented; abdomen with at least 9 segments and
with stylet-like appendages on ventral side of some segments; without
a forked appendage near end of abdomen, but with well-developed cerci
(diplurans)
Diplura
(b)
Antennae short, with 6 or fewer segments; abdomen with 6 or fewer segments
and usually with a forked appendage near posterior end
(springtails)
Collembola
(a)
Body larviform, thorax and abdomen not differentiated; compound eyes
present (larviform female beetles)
Coleoptera
Body shape variable; if larviform, then without compound eyes
55
(b)
55.
124
(a)
(b)
Compound eyes usually present; body shape variable, but usually not
wormlike; wing pads often present (adults and nymphs)
Compound eyes and wing pads absent; body usually wormlike in shape
(larvae)
54
56
65
56.
(a)
(b)
Tarsi 5-segmented
Tarsi with 4 or fewer segments
57.
(a)
Mouthparts prolonged ventrally into a snoutlike structure; body more or less
cylindrical and usually less than 15 mm in length
(wingless scorpionflies)
Mecoptera
Mouthparts not as above body shape and size variable
58
(b)
58.
(a)
(b)
59.
(a)
(b)
Antennae 5-segmented; Some female twisted-winged parasites
Mengidae
Antennae with more than 5 segments;
Walking sticks and some cockroaches
Cerci forcepslike; tarsi 3-segmented
Cerci absent or, if present, not forcepslike; tarsi variable
57
59
Strepsiptera
Orthoptera
60
61
Practical 16: Systematic Entomology
60.
(a)
(b)
61.
(a)
(b)
62.
63.
Antennae more than half as long as body; cerci short;
Timemidae
Antennae usually less than half as long as the body; cerci long;
(earwigs)
Dermaptera
Tarsi 3-segmented, basal segment of front tarsi enlarged
(webspinners)
Tarsi 2-to 4-segmented, basal segment of front tarsi not enlarged
Embioptera
62
Orthoptera
(a)
Grasshoppper-like insects, with hind legs enlarged and fitted for jumping;
length usually over 15 mm(grasshoppers)
Orthoptera
(b)
Not grasshopper-like, hind legs usually not as above; length <10 mm
(a)
Tarsi 4-segmentd; pale, soft-bodied, wood-or-ground-inhabiting insects
Termites
Isoptera
Tarsi 2-or-3-segmentedl; colour and habitats variable
64
(b)
64.
125
63
(a)
Cerci present, 1-segmented, and terminating in a long bristle; antennae
9-segmented and moniliform; compound eyes and ocelli absent; tarsi
2-segmented (zorapterans)
Zoraptera
(b)
Cerci absent; antennae with 13 or more segments and usually hairlike;
compound eyes and 3 ocelli usually present; tarsi 2-or-3-segmented
(psocids)
Psocoptera
65.
(a)
(b)
Ventral prolegs present on 2 or more abdominal segments
Abdominal prolegs absent or on terminal segment only
66.
(a)
With 5 pairs of prolegs (on abdominal segments 3-6 and 10) or fewer,
the prolegs with tiny hooks (crotchets); several (usually 6) ocelli
on each side of head (caterpillars, butterfly and moth larvae)
Lepidoptera
With 6 or more pairs of abdominal prolegs, the prolegs without crotchets;
number of ocelli variable
67
(b)
67.
68.
(a)
Seven or more ocelli on each side of head; prolegs on segments 1-8 or 3-8,
usually inconspicuous pointed structures (scorpionfly larvae)
Mecoptera
(b)
One ocellus on each side of head; prolegs fleshy and not pointed, usually
on abdominal segments 2-8 and 10 sometimes on 2-7 or 2-6 and 10
(sawfly larvae)
Hymenoptera
(a)
Mandible and maxilla on each side united to form a sucking jaw that is
often long; tarsi with 2 claws; labrum absent or fused with head capsule;
maxillary palps absent
(planipennia: larvae of lacewings and antlions
Neuroptera
Mandibles and maxillae not as above; tarsi with 1 or 2 claws; labrum
and maxillary palps usually present
69
(b)
69.
66
68
(a)
(b
Head and mouthparts directed forward (prognathous), the head about as
long along midventral line as along mid-dorsal line and usually cylindrical
or somewhat flattened
70
)Head and mouthparts directed ventrally (hypognathous), the head much longer
along mid-dorsal line than along midventral line and usually rounded
72
Practical 16: Systematic Entomology
70.
(a)
(b)
Tarsi with 1 claw (some beetle larvae)
Tarsi with 2 claws
71.
(a)
A distinct labrum and clypeus present (not Australian!)
(Raphidiodea: snakefly larvae)
Labrum absent or fused with head capsule
Most adephaga: beetle larvae
(b)
72.
73.
126
Coleoptera
71
Neuroptera
Coleoptera
(a)
Front legs distinctly smaller than other pairs; middle and hind legs projecting
laterally much more than front legs; a small group of ocelli (usually 3) on
each side of head behind bases of antennae; tarsal claws absent; length less
than 5 mm; usually found in moss (larvae of Boreidae)
Mecoptera
(b)
Legs not as above, front and middle legs about the same size and position;
ocelli variable; tarsi with 1-3 claws; size and habitat variable
(a)
(b)
73
Tarsi with 1 or 2 claws; abdomen usually without caudal filaments;
antennae variable (beetle larvae)
Coleoptera
Tarsi usually with 3 claws; abdomen with 2 caudal filaments about one
third as long as body; antennae usually short and 3-segmented
(triungulin larvae and some beetles (Meloidae) and twisted-winged
parasites)
Coleoptera and Strepsiptera
74.
(a)
(b)
Aquatic (fly larvae)
Not aquatic, but terrestrial or parasitic
75.
(a)
Sessile, plant feeding; body covered by a scale or waxy material; mouthparts
haustellate, long and threadlike (female scale insects)
Homoptera
Not exactly fitting the above description
76
(b)
76.
77.
78.
(a)
Head and thorax more or less fused, and abdominal segmentation indistinct;
internal parasites of other insects (female twisted-winged parasites) Strepsiptera
(b)
Head not fused with thorax, body segmentation distinct; habitat variable
77
(a)
(b)
Head distinct, sclerotized, and usually pigmented and exserted
Head indistinct, incompletely or not at all sclerotized, sometimes
retracted into thorax
78
85
Head and mouthparts directed forward (prognathous), the head about as
long along midventral line as along middorsal line and usually cylindrical
or somewhat flattened
79
Head and mouthparts directed ventrally (hypognathous), the head much
Longer along middorsal than along midventral line and usually rounded
82
(a)
(b)
79.
(a)
(b)
80.
Diptera
75
(a)
(b)
Terminal abdominal segment with a pair of short pointed processes; several
long setae on each body segment (flea larvae)
Siphonaptera
Not exactly fitting the above description
80
Labium with a protruding spinneret; antennae arising from membranous area
at bases of mandibles; mandibles well developed, opposable; body usually more
or less flattened ventral prolegs usually with crotchets; mostly miners in leaves,
bark or fruits (moth larvae)
Lepidoptera
Labium without a spinneret, antennae, if present, arising from head capsule;
Prolegs without crotchets
81
Practical 16: Systematic Entomology
81.
82.
83.
84.
85.
86.
87.
127
(a)
Mouthparts distinctly mandibulate, with opposable mandibles; spiracles usually
present on thorax and 8 abdominal segments; body shape variable
(beetle larvae)
Coleoptera
(b)
Mouthparts as above or with mouth hooks more or less parallel and moving
vertically; spiracles variable, but usually not as above, body elongate
(fly larvae, Nematocera and some Brachycera)Diptera
(a)
Abdominal segments usually with 1 or more longitudinal folds laterally or
lateroventrally; body C-shaped, scarabaeiform; 1 pair of spiracles on thorax
and usually 8 pairs on abdomen (white grubs: beetle larvae)
Coleoptera
(b)
Abdominal segments without longitudinal folds, or if such folds are present,
then spiracles not as above
83
(a)
Head with adfrontal areas; labium with a projecting spinneret; if present,
antennae arising from membranous area at base of mandibles; often 1 or more
(usually 6) ocelli on each side of head; ventral prolegs, if present, with crotchets
(moth larvae)
Lepidoptera
(b)
Head without adfrontal areas, and labium without a spinneret; antennae and
ocelli not as above; prolegs, if present, without crotchets
84
(a)
Mandibles not heavily sclerotized and not brushlike; spiracles usually present
on thorax and most abdominal segments, the posterior pair not enlarged;
larvae occurring in wet places, in plant tissues, as parasites, or in cells
constructed by adults (Apocrita)
Hymenoptera
(b)
Mandibles usually brushlike; spiracles usually not as above-if present on
several abdominal segments, the posterior pair is much larger than the others;
occurring in wet places, in plant tissues, or as internal parasites
(fly larvae, mostly Nematocera)
Diptera
(a)
Mouthparts of the normal mandibulate type, with opposable mandibules and
maxillae antennae usually present (beetle larvae)
Coleoptera
(b)
Mouthparts reduced or modified, with only the mandibles opposable, or with
parallel mouth hooks present; antennae usually absent
86
(a)
Body behind “head” (first body segment) consisting of 13 segments; full-grown
larvae usually with a sclerotized ventral plate (the “breast-bone”) located
ventrally behind head (larvae of Cecidomyiidae)
Diptera
(b)
Body consisting of fewer segments; no breast-bone
(a)
Mouthparts consisting of 1 or 2(if 2, then parallel, not opposable) median,
dark-coloured, decurved mouth hooks
(maggot: larvae of Cyclorrhapha)
Diptera
Mandibles opposable, but sometimes reduced, without mouth hooks such
as described above (larvae of Apocrita)
Hymenoptera
(b)
87
Practical 16: Systematic Entomology
128
Practical 17: Echinodermata 1
PRACTICAL 17
129
ECHINODERMATA 1
MATERIAL AVAILABLE
Preserved specimens:
All available dried and preserved echinoderms
Live or narcotised material:
Representatives of all classes of echinoderms
Househhold bleach: small amount in bottle with Pasteur pipette
AIM
To illustrate the diagnostic features of each of the classes of echinoderms.
PREPARATORY READING
•
•
The chapter on echinoderms in your textbook, concentrating on the
diagnostic characteristics of the five extant classes.
Read the notes below (LABORATORY TASKS) for this practical in conjunction
with your text book and its illustrations.
LABORATORY TASKS
1.
Diversity of echinoderms
Examine the living and preserved examples of members of the five major extant
classes of echinoderms. With the help of text books, make detailed observations on
the following features and compile the table on the last page of these notes to
compare and contrast the classes.
symmetry
oral/aboral surfaces
mouth and anus
water vascular system including:
•
•
•
position of madreporite*,
arrangement of the ambulacral and interambulacral areas
the form of the: ambulacral groove*, oral tube feet and tube feet* noting
their location, arrangement and shape
presence/absence of suckers and role in feeding and locomotion
pedicellaria* - noting types and structure
respiratory structures* - papillae and branchiae
skeletal system* - including test, spines, any conspicuous elements (e.g. jaws),
size and arrangement of ossicles
* these structures require detailed examination as outlined in the following instructions.
Practical 17: Echinodermata 1
130
Symmetry
Most echinoderms show penta-radial symmetry, but there are exceptions.
Oral/Aboral Surfaces
The oral surface of an echinoderm is defined by the presence of the mouth and tube
feet, whereas the aboral surface has no tube feet. Delineate these two surfaces in
each of the five classes and note whether or not the oral surface faces downwards.
Mouth/Anus
Although all echinoderms have a mouth, the position of which marks the oral
surface, not all echinoderms have an anus, and those that do have them do not
necessarily have them on the aboral surface.
Water Vascular System
a.
Madreporite
The madreporite is a skeletal plate that marks the entrance to the water vascular
system. It is also referred to as the sieve plate, because of its porous nature. It
may be oral, aboral or internal.
b.
Ambulacral Areas and Grooves
The ambulacral areas are defined by the position of the paired rows of tube feet
that project through the body wall. Each pair of rows lines a so-called
ambulacral groove. The area between adjacent grooves is called the
interambulacral area.
An ambulacral groove may be open or closed, depending on the position of the
radial and lateral canals of the water-vascular system, relative to the ossicles in
the body wall. Open ambulacral grooves appear as a furrow along the body
surface whereas closed ambulacral grooves show a flat body surface.
c.
Tube feet - the external evidence of the water vascular system
Examine a living specimen of a starfish, brittle star, holothuroid, and echinoid,
noting in particular these aspects of the structure and function of the tube feet:
numbers, size and extensibility of tube feet, nature of the distal end of the tube
foot, operation of the sucker, response to stimulations. These observations
should be made using the dissecting microscope to view specimens immersed in
seawater.
Using a depression slide, observe the sucker of the tube foot of a star-fish and
sea urchin. The urchin sucker has a skeletal support structure. The fine details
of this may be seen by introducing household bleach under the coverslip and reexamining the slide after half an hour.
Examine a small living crinoid using a dissecting microscope; look at the tube
feet used in feeding. These are arranged in triplets of unequal length.
Practical 17: Echinodermata 1
131
Pedicellaria - defensive organs in echinoids and some asteroids.
Using a dissecting microscope observe the surface of several starfish, and urchins
to find pedicellaria. Not all starfish have pedicellaria, but there are sessile 2-bladed
pedicellaria on some species (visible on dried specimens), as well as stalked 2bladed pedicellaria on others. Find examples of both types, and stimulate them
with the end of a dissecting needle and note how they respond.
Prepare some stalked pedicellaria for microscope examination using a depression
slide. Bleach will dissolve the flesh to reveal the skeletal elements which make up
the pedicellaria.
Echinoids have several types of pedicellaria, located on stalks among the bases of
the spines. Examine the sensitivity and structure of these pedicellaria as you did
for the asteroid ones.
Respiratory structures
Echinoderms have various structures which increase epithelial surface area and
decrease the distance between coelomic fluid and seawater.
Examine specimens of forcipulate and phanerozoic starfish. The respiratory
structures, papulae, or dermal branchiae, are visible as evaginations from the
aboral surface of starfish exposed to exterior (forcipulate) or protected by paxillae
(phanerozoic). The coelomic fluid circulates in the papulae as indicated by
movement of particles visible in the fluid.
Examine the oral region of a sea urchin to locate the gill like structures which may
act as respiratory organs.
Skeletal elements
Dissolving the flesh from whole echinoderms leaves the skeletal elements all
disarticulated. Examine the skeletal elements from a whole echinoid, holothuroid,
ophuroid and asteroid, using microscopes as required. Spines are endoskeletal
elements. Examine specimens of each class of echinoderm, noting the presence,
position and abundance of spines and, on live specimens, their movements.
OUTCOMES
1. You will be able to name and locate the externally visible parts of the water
vascular system in examples of each of the five living classes of echinoderms.
2. You will be able to name, recognize, and locate the defensive organs in echinoids
and some asteroids.
3. You will be able to name, recognize, and locate the respiratory organs in
echinoids and some asteroids.
4. You will be able to recognize some of the skeletal elements that are characteristic
of the five classes of living echinoderms.
5. You will be able to identify members of the phylum Echinodedrmata to class.
6. You will have a good understanding of the principal components of the
echinoderm anatomy and be able to apply that to the identification of
echinoderms.
Practical 17: Echinodermata 1
Character
Ambulacral
Groove
Spines
Pedicellaria
Madreporite
Anus
132
Crinoidea
Asteroidea
Ophiuroidea
Echinoidea
Holothuroidea
133
Practical 18: Echinodermata 2
PRACTICAL 18
PHYLUM ECHINODERMATA 2
MATERIAL AVAILABLE
Preserved specimens:
Disarticulated ossicles of Aristotle’s lantern, tests and spines of E. mathaei
Tests of Heliocidaris erythrogramma
Live or narcotised material:
Heliocidaris erythrogramma – one per two students
AIM
To illustrate the internal features of echinoderms, particularly the water vascular
system.
PREPARATORY READING
•
•
Sections of your textbook covering the general anatomy of echinoderms.
The notes below (LABORATORY TASKS) in conjunction with your readings in
the text book and its illustrations.
LABORATORY TASKS Dissection of Heliocidaris erythrogramma.
External Anatomy
Immerse a narcotised specimen in seawater and use your dissecting scope and
illuminators to provide a well-lit magnified view. Obtain a dried urchin test to help
you understand the relationship of the structures to the skeleton. Use the
diagrams in your textbook to help you locate the following structures.
On the oral surface, find the central mouth with the five teeth protruding from the
internal jaw apparatus. The mouth has a rough, flexible lip, surrounded by a soft
membrane, the peristome. There are ten small calcareous plates embedded in the
peristome, and these are pierced by large buccal tube feet that appear in a ring on
the surface of the peristome. These are sensory organs, probably used for tasting.
Each is surrounded by clusters of pedicellaria and small spines. At the outer edge
of the peristome are ten branching so-called gills. These are contractile and
strongly ciliated, and their cavities open into the coelomic cavity of the jaw
apparatus (Aristotle’s lantern).
At the edge of the flexible peristome, the hard test begins. It is covered by an
external, ciliated epidermis from which protrudes long and short movable spines
and several types of pedicellaria. Make out the five double rows of tube feet
extending from the oral surface around to the aboral pole. The rows of tube feet
mark the position of the five ambulacral areas of the test and these alternate with
five interambulacral areas.
Practical 18: Echinodermata 2
134
On the aboral surface, notice that the test extends almost to the aboral pole. There
is a small flexible area at the pole, the periproct, with the opening of the anus,
which may be obscured by converging spines. The test around the periproct
contains the genital plates, one of which is enlarged and perforated with small
holes. This is the madreporite, the opening to the water vascular system.
Examine the dried urchin test and find the position of the peristome and periproct.
On the genital plates and madreporite make out the genital openings (gonopores)
and the smaller openings of the water vascular system. Most of the plates have
tubercles that are the points of articulation of the test with the bases of spines.
Notice that there are several sizes, corresponding to the sizes of the spines. Identify
the ambulacral and interambulacral areas and notice that the plates in the
ambulacral areas are perforated with pairs of pores, through which the tube feet
protrude. Note how the individual plates join together to make up the test. The
number of plates increases as the urchin grows, with new plates added at the
aboral end, and each plate also increases in size around its margin.
Internal Anatomy
Using sharp, strong scissors, make a cut around the equator of the test. This may
be easier to do if you use the secateurs to remove some of the spines first.
Gently dislodge the gonads from the inside of the aboral part of the test by
inserting a blunt probe between the test and gonads and scraping the connective
tissue away. Leave them connected to the test at their aboral tip. Then carefully
break away fragments of the aboral half of the test until all that remains is a disk
about the size of a 10c piece around the anus.
After cleaning away all scraps of test and loose tissue, place your dissection in a
dish of clean seawater. This will float the delicate tissues and allow you to see
them in their proper shape. Without further dissection, view your specimen under
the dissecting scope.
Reproductive System
There are five yellow gonads which join aborally. The gonads are in the
interambulacral areas and are held in place by their mesenteries.
Tilt the urchin so that you can look between the gonads and the disk of remaining
test. The gonads connect to the five genital pores by thin strands of tissue or
gonoducts.
Beneath this piece of test also notice the opening of the anus in the periproct, the
madreporite and the stone canal leading down from the madreporite to the
circum-oral water ring on top of the Aristotle's lantern.
Practical 18: Echinodermata 2
135
The Alimentary Canal
The purple gut is attached to the interambulacral areas by mesenteries. The
arrangement of the gut is complicated, notice that it makes 2 circuits of the
circumference of the animal. If the urchin has fed recently its gut will be full of
small pellets of food and faeces. The gut ruptures easily so your dissection may be
contaminated by the gut contents. Rinse these away with changes of seawater.
Emerging from the top of the Aristotle's lantern is the purple oesophagus. It and
the axial organ and the rectum are connected together by a sheet of connective
tissue. These details maybe obscured by the gonad. If so, carefully pick away
some of the tissue of the gonads until the oesophagus, stone canal and axial organ
are revealed.
Dissect away the gonad to reveal the course of the gut anteriorly from rectum to
oesophagus. From the rectum the gut passes as the intestine in a counter
clockwise direction viewed from above, looped around the inner wall of the test for
360°. The gut then reverses direction and loops 360° in a clockwise direction
towards the oesophagus. Remove more of the gonad so that the oesophagus, its
connection to the stomach and the proximal part of the stomach are exposed.
Find the junction between oesophagus and stomach. The oesophagus is a robust
tube; the stomach is delicate, thin-walled, and a slightly different colour. Notice
that the oesophagus divides into two parts: one enters the stomach, but the other
branch, the siphon, remains as a separate tube, but is appressed to the inner
border of the stomach wall. Follow the course of the siphon along the wall of the
stomach until the siphon enters the stomach where the stomach ends and the
intestine begins. (It is suggested that the siphon functions as a bypass for excess
water taken in with the food.) The intestine is a darker colour than the stomach.
This runs into the rectum, a large dark tube of tissue covering the inside surface of
the periproct.
The Water Vascular system
On one side of the rectum find an attached strand of tissue leading downwards
from the madreporite. This is the stone canal which separates from the rectum
and joins a sausage-shaped, orange organ, the axial organ. The axial organ ends
close to the top of the Aristotle's lantern, and the stone canal, which is fastened to
the axial organ, connects to the circum-oral water ring at the top of the lantern.
Relocate the axial organ and the stone canal and trace their path along the
oesophagus to the circum-oral water ring. Note that closely associated with the
circum-oral water ring is a second tubular system which gives rise to two strands of
tissue which pass along the walls of the oesophagus. These, and the axial organ,
are parts of the haemal system.
The circum-oral water vascular ring lies in connective tissue covering the top of the
Aristotle's lantern. The ring has 5 sacculated polian vesicles appended to it.
These lie in the transparent connective tissues and are seen as shadowy shapes in
the interambulacral fields of the tissue below the flexible dental sacs which
protrude from the top of the lantern.
Practical 18: Echinodermata 2
136
The water vascular ring also gives rise to five radial canals in the ambulacral areas.
The origin of these canals is obscured by the tissue on top of the lantern, but they
emerge at the base of the lantern, forming the centre of the two rows of ampullae
which mark the ambulacral areas. These are columns of triangular leaflets. Their
appearance is reminiscent of the leaflets of the molluscan ctenidium.
Aristotle’s lantern
A thin peritoneum covers the whole jaw apparatus, thus separating its coelomic
cavity from the perivisceral cavity.
On top of the jaw apparatus (also known as Aristotle's lantern) identify the five
narrow ossicles known as the radii (also called compasses), each of which is joined
by two ligaments to the base of the peristome and by muscles to the neighbouring
radii.
Opposite each interambulacrum, the peritoneum bulges upwards to form a thinwalled vesicle called a dental sac (this may be considered as an internal gill,
transferring oxygen to the jaw muscles from the perivisceral coelom). Inside each
dental sac is the curved upward extremity of one of the teeth.
Identify the retractor muscles attached to the auriculae (which arch over the
ambulacral area on the inside of the test at the edge of the peristome); these pull in
the teeth and so open the mouth, and the protractor muscles extending from
between the auriculae to the upper edge of the jaw apparatus; these push out the
teeth and so close the mouth.
Detach the jaw apparatus by cutting through the muscles, the ligaments, and the
peritoneum, and also through the lip round the edge of the mouth. Notice that the
radial water vascular canals, leaving the base of the jaw apparatus, cross the inner
surface of the peristome, each giving two branches without ampullae to the buccal
tube feet.
OUTCOMES
1.
You will understand the structure and function of the reproductive,
alimentary and water vascular systems in echinoderms
2.
You will have some knowledge of the complexity of the Aristotle’s lantern and
a basic understanding of how it functions.
Practical: 19: Protochordates
PRACTICAL 19
137
PROTOCHORDATES
MATERIALS REQUIRED
Prepared slides:
Amphioxus: whole mount, pharynx, liver and ovary, intestine, caudal
Chaetognatha: whole mount
Preserved specimens:
Hemichordata: Balanoglossus
Pterobranchia
Cephalochordata: Amphioxus
Urochordata: ascidian tadpoles, colonial ascidians, Thaliacea, Pyrosoma, Salps,
Doliolids and other planktonic forms
Live or narcotised material:
Large solitary ascidians for dissection – one per two students
Hemichordates
Solitary and colonial ascidians
AIMS
1.
To illustrate the morphology of animals belonging to the Phyla Chaetognatha and
Hemichordata, and the subphyla Cephalochordata and Urochordata of the Phylum
Chordata;
2.
To examine carefully by dissection, the structure of a solitary ascidian;
3.
To illustrate characteristics of thaliaceans.
PREPARATORY READING
1.
Read LABORATORY TASKS in conjunction with your text book (part 2 below),
referring to the cited figures so that you will have an idea of the structures that you
should see in the material in the practical session. This preparation is essential so that
you can be effective and efficient in carrying out the Laboratory Tasks in the 2 hours
of the practical session
Read the sections covering each of the three phyla in your textbook.
Practical: 19: Protochordates
138
LABORATORY TASKS
1. Phylum Chaetognatha
Examine the prepared slides of Saggita and distinguish the features illustrated in your text
book. Examine some preserved whole specimens to supplement the slide material if
available.
2. Phylum Hemichordata, class Enteropneusta: Acorn worms
a. Examine a preserved or living specimen of an enteropneust and note these major external
features. The body is divided into an anterior proboscis, a middle collar, and a posterior
trunk. The trunk is divided into an anterior branchio genital area with gill slits and genital
wings, and a posterior cylindrical abdominal region. Find the mouth which opens
between the proboscis and the collar on the ventral side. The gill slits open on the dorsolateral walls of the trunk.
b. In the living specimens note the action of the proboscis. It cannot retract, completely, but
does often seal against the collar to obscure the mouth.
c. In preserved specimens trace the alimentary tract from the mouth to the pharynx, and
convince yourself of the connection between pharynx, gill slits and the outside of the
worm.
3.
Phylum Chordata, Subphylum Cephalochordata: Amphioxus
a. Examine a preserved specimen and the microscope slide of Amphioxus whole mount. The
body is bilaterally compressed, pointed at both ends, and without appendages. The
anterior end is blunter than the sharply pointed posterior
The rostrum forms the anterior point of the body. The oral hood is two flaps which hang
down on each side of the mouth. A dorsal fin runs the length of the dorsal side of the
body, and a ventral fin is along the posterior third of the body. The anterior two-thirds of
the body has latero-ventral metapleural folds. The atrial opening is at the anterior end of
the ventral fin and the anus opens on the left of the caudal fin which is an expansion of the
dorsal and ventral fin at the posterior end of the body. The > -shaped lines on the sides of
the body are connective tissue septa which divide the lateral muscles into myotomes. The
myotomes alternate on the left and right sides of the body; they are indicative of the
number of body segments present. The gonads are ventro-lateral and may be seen through
the body wall of mature animals.
b. Examine the cross section slides of Amphioxus at the pharynx, liver and ovary, intestine
and caudal end. From these work out the 3-dimensional arrangement of the internal
organs.
i. Since the pharyngeal slits are not exactly vertical, the sections cut through several;
ii. The midgut caecum (= liver) projects forward from the gut to lie below the pharynx;
iii. There is a fin ray in the dorsal fin, and then ventrally there are the following organs:
neural tube, notochord, dorsal aorta, gut.
iv. The cross sections cut through several myomeres, which are lateral blocks of muscular
tissue.
Practical: 19: Protochordates
139
4. Phylum Chordata, Subphylum Urochordata Class Ascidiacea, Sea squirts.
a. Examine the living solitary ascidian with a thin transparent test, in a bowl of seawater
under a dissecting microscope. The body is covered by a semi-transparent tunic which is
secreted by the epidermis. The basal end of the tunic is a holdfast which attaches the
animal to the substratum. The distal end of the animal has two openings; the larger
buccal opening is terminal and the atrial opening is sub-terminal. These openings can be
closed by sphincter muscles; the buccal opening may have tentacles which form a coarse
sieve to the inhalant current of water. The cerebral ganglion lying in the body wall
between the buccal and atrial openings may be seen if the tunic is transparent enough.
The distal part of the body below the buccal cavity consists of the pharynx. The intestine,
stomach, heart, and gonads lie at the base of the pharynx at the proximal end of the sea
squirt. The anus and ducts from the gonads open into the atrial cavity below the atrial
opening.
b. Set a specimen aside in a bowl of seawater until it relaxes and begins filtering water.
Introduce a pasteur pipette containing suspended carmine particles near the buccal
(inhalant) opening and release a drop of the carmine solution. Observe the passage of the
carmine into the buccal opening over the pharynx and into the gut.
c. Select a narcotised sea squirt for dissection.
i.
Remove the tunic by first making a longitudinal cut just below the atrial siphon, deep
enough to cut through the tunic without puncturing the underlying body wall, and then
cut down around the base and up to the buccal siphon.
ii.
Carefully lift the top half of the tunic, teasing it away from the body wall and cutting
through the tunic between the buccal and atrial siphons as necessary. As the body wall
of some ascidians contains irritating spicules, check for these and if they are present,
wear rubber gloves or take care not to handle the animal without dissecting instruments.
iii.
Remove the animal from the remaining tunic and place it in a bowl of seawater.
iv.
Before dissecting further, check the position of the body organs (refer to figure). The
pharynx occupies almost all of one side of the animal and on the atrial side the
oesophagus can be seen leaving the pharynx about two-thirds of the way down its edge.
This widens into the stomach which appears brown through the body wall. Just below
the stomach, right at the base of the animal, the ribbon-like heart should be visible
through the transparent pericardium. Note the extent of the heart along both sides of the
body and note the frequency and direction of its pulsations.
v.
The small intestine passes from the stomach, up towards the buccal opening then loops
downwards, widening into a sac-like large intestine. From this the rectum passes
upwards, ending with the anus just below the atrial opening.
vi.
The gonads are situated in the loop of the small intestine and one or two gonoducts can
be seen passing down between the small and large intestine, then crossing the large
intestine to follow the rectum towards the atrial opening.
Practical: 19: Protochordates
vii.
140
Once the arrangement of these organs is understood, turn the animal over and cut the
pharynx open along its full length. Notice the grooved endostyle on the buccal side and
the dorsal languets or lamina along the atrial side. Remove a small piece of the
pharyngeal wall and examine it in a depression slide under the compound microscope.
The pharyngeal slits have been elaborated into patterned openings called stigmata.
Find the opening from the pharynx into the oesophagus and cut along the oesophagus
into the stomach. Note the longitudinal ridges, probably glandular.
d. Colonial Ascidians
Many ascidians are colonial: they bud off new individuals and the whole colony is embedded
in a common test . Each individual may have a separate inhalant (buccal) and exhalant (atrial)
opening in the tunic, but often several individuals share a common atrial pore. The pattern of
arrangement of individuals around the common atrial pore is a distinguishing feature.
Practical: 19: Protochordates
141
Examine the preserved and living specimens of colonial ascidians. Each individual is much
smaller than the solitary individuals you dissected. Cut thin sections of the preserved
specimen perpendicular to the surface of the colony and examine these with a dissecting
microscope to determine the orientation of the individuals and the arrangement of the organs.
Observe the living specimens with dissecting microscopes and determine the pattern of water
flow by introducing drops of carmine containing seawater near the colony.
5. Class Thaliacea: pyrosomids, doliolids and salps
These animals are pelagic marine organisms. They have buccal and atrial openings at
opposite end of the body.
Pyrosomids are colonial animals in which the colony is a hollow cylinder closed at one end.
The individual zooids are in the walls of the cylinder and their atria discharge into the centre
of the cylinder . The colonies are phosphorescent. Examine the preserved specimens.
Doliolids and salps are solitary animals with complicated alternation of generation life cycles
(refer to lecture notes and texts). Like the pyrosomids, their buccal and atrial openings are on
opposite ends of the body. The tunics of these animals are transparent, and the characteristic
muscle bands and internal organs are visible.
a. Examine the preserved specimens of doliolids and salps noting the following: the oozooid
and blastozooid body forms, the pharyngeal clefts, the oral/atrial aperture, the muscle
bands (shape and number), and cadophore (present/absent).
SELF ASSESSMENT EXERCISE
1.
Construct a table which compares and contrasts the pharyngeal regions of
enteropneusts, Amphioxus and ascidians.
2.
Compare the alternation of generations in cnidarians and urochordates.
Practical: 19: Protochordates
142
Practical: 20: Larval stages
PRACTICAL 20
101
LARVAL AND PLANKTONIC STAGES
MATERIALS REQUIRED
Live material:
Freshly collected plankton samples
Slide material
Prepared slides of the early life stages of Cnidaria, Platyhelminthes, Phoronida etc as
available
AIMS
1.
To find and identify larvae and other planktonic stages of the common marine phyla
2.
To revise the larval and juvenile stages of all phyla
PREPARATORY READING
Brusca and Brusca and Ruppert, Fox and Barnes both have details of the larval forms at the
end of each chapter of their texts, but Pechenik has a whole chapter (Chapter 24) devoted to
the consideration of invertebrate reproduction and development. You should try to read this
chapter before the laboratory session. You will receive a handout of the relevant diagrams.
PREAMBLE
Most marine invertebrates have a planktonic life stage and some spend all of their lives in the
plankton. The planktonic stage is usually a dispersive stage, allowing propagules to be
transported to new sites to settle and establish new populations. Settlement usually involves
metamorphosis from the mobile larval form to a sessile or sedentary adult. Because of the
differences in their habitat and life style, larvae often look quite different from the adults that
produced them. Thus it is often difficult to match larvae with their adult counterparts.
This is also true for terrestrial and parasitic invertebrates that show indirect development and
whose larvae and adults use different habitats. Today’s practical is also an opportunity for
you to revise your knowledge of the early stages of all phyla dealt with this semester.
LABORATORY TASKS
A. Plankton samples
A freshly collected plankton sample will be available in the laboratory. You should take up
small amounts of seawater with a pipette and transfer into a small shallow petri dish or onto a
depression slide. Survey the sample first with your dissecting microscope and then your
Practical: 20: Larval stages
102
compound microscope. Take many samples in order to see as many types of animals as
possible. Make drawings or take pictures of as many different types as possible.
1. Phylum Cnidaria
Medusae of the hydroid Obelia are often found in the plankton samples. Note that they
are not larvae. What life stage do they represent?
2. Phylum Annelida
Annelids have trochophore larvae but it is more usual to see a slightly later stage in the
plankton. These are known as setigerous larvae. They may still have cilia on the head,
but have the beginnings of segments and are covered with chaetae.
3.
Phylum Mollusca
Molluscs also have trochophore larvae but it is more usual to find veliger larvae of either
gastropods and bivalves in the samples.
4.
Phylum Bryozoa
Bryozoans have two types of larvae and it is the cyphonautes type that we find more
often.
5.
Phylum Arthropoda
Crustaceans form a very large proportion of the biomass of the plankton and most of
those are adult forms. You should be able to identify these to class and possibly order.
However there will also be larval forms present. The nauplius larva of both copepods
and barnacles are common and the zoea larva of the decapod crabs will also be found.
6.
Phylum Chaetognatha
These planktonic (adult) animals are sometimes seen in the plankton samples. Note that
they themselves do not have a larval stage, being direct developers.
6.
Phylum Echinodermata
Echinoderms have many different larval types but the ophiopluteus larva of the brittle
stars is more common in the samples.
7.
Phylum Chordata, Sub-phylum Urochordata
Class Ascidaceae: very occasionally the tadpole larvae of the sea-squirts are seen in the
plankton samples. They can be recognized by their tiny branchial baskets and
attachment organs
Class Larvaceae: these are more common in the plankton. What life-stage do they
represent?
B. Other larval stages
Take the opportunity to revise your knowledge of other early stages that were covered in the
practicals during semester. You will be expected to recognize larval forms on sight.