Arthropod survey.
Part one.
Aquatic crustaceans
Please examine tagmata and locomotion in three different crustaceans. You
should obtain a picture of each and be able to describe the types, number
of appendages and how they and other structures are used in locomotion
in each species. Are they using the whole appendages as the “effective”
leg or just part of it to move? Your pictures should label antennae and
“legs”. Your descriptions should include any tagmata you can see.
All containers should be rinsed with spring water before organisms are placed in
them.
Daphnia
Everyone should look at locomotion in Daphnia, the common water flea. These are
highly transparent organisms and you can easily a. compare their anatomy
to that of the Caprellid shrimp of last week. Are any females carrying eggs?
Daphnia when crowded becomes pink to red as it develops hemoglobin. Can
you think of any reasons for this? Is there any evidence that our cultures have
individuals that have developed hemoglobin?
Also make sure you can describe in some detail how Daphnia uses its
appendages to move. Compare the way Daphnia moves to that of the Caprellid
shrimp or glass shrimp. Obtain a movie of Daphnia movement.
A reference diagram for Daphnia
Examine the isopods and one of the other aquatic crustaceans available.
Freshwater isopod. a. Obtain a photograph and b. label regions and c. describe
how appendages are used in locomotion. d. You will compare these fresh
water isopods to the terrestrial isopods or pill bugs. As in most crustaceans,
the isopod body is divided into three distinct regions: head (= cephalon), thorax
(=pereon), and abdomen (= pleon). Please use the more general terms, head,
thorax and abdomen for labels on your photograph.
You may choose between freshwater crayfish, amphipods or freshwater
copepods or saltwater copepods as your third crustacean in which to
examine locomotion. There may be extra points if you can get movies of
locomotion in some of these. All species move rather quickly.
Choices available
Freshwater amphipods.
a. Obtain a photograph and b. label regions, head, thorax and abdomen and c.
describe how appendages are used in locomotion.
or Freshwater or saltwater Copepod. Cope is greek meaning an “oar” or “paddle;”
pod is Greek for “foot.” This should serve as a hint for how these individuals
move. You will probably find copepods on most of the marine specimens you will
view in the future and so you need to be able to recognize these small animals.
a. Obtain a good image of a copepod for your journal. You may have to
place a copepod on a slide under the light microscope to obtain a good
image. b. Describe how these animals locomote.
We do have marine copepods, which are bigger than freshwater forms, that you can
examine. However, do not mix salt water with fresh. Rinse your dishes with
several washes of spring water after viewing marine copepods. Marine
specimens can tolerate some fluctuations in salinity. Your freshwater specimens
however cannot be put in salt water
Or.
Freshwater crayfish. We keep a Procambarus sp. first found in Germany. It is an
unusual species in that males are lacking. This variety is know for being
parthenogenetic. Meiosis is suppressed in females, who essentially clone
themselves whenever they produce eggs.
Unfortunately, none of our females are carrying eggs. However, if you wish to use one
of these for examining locomotion in fresh-water crustacean, feel free to do so.
Take good notes, as you will not be able to film these species. Those of you with
smart phones may want to click a few shots and email the pictures to yourself for
your journal.
----------------------Ostracods
We do not have ostracods today, but a diagram of these animals is included because
you may also see a number of marine ostracods on your specimens in the future.
An ostracod is a segmented crustacean with head, thorax and abdomen. The
head has very hairy legs and usually at least one eye. The rest of the body is
very short and ends in a multi-pronged tail (furca). The whole body is enclosed in
the carapace, which hinges on the back and is held shut by strong muscles.
Sometimes the antennae can be extruded through a notch at the front. Most
ostracods are very small, fewer more than 4 mm long but some deep-water
pelagic species grow to 30 mm.
Sexy shrimp
Before you begin to work with terrestrial forms, check on the sexy shrimp, Thor
amboinensis, in the aquarium. These animals sways their abdomens back and
forth in a style determined sexy, hence their name. Many functions have been
postulated for the swaying, among them territorial defense, mating, etc. You
may have used them as a model for locomotion last week. Do you notice any
groupings? Are the animals more active in groups?
Before moving on to an examination of terrestrial arthropods, your instructor
should with the class compare and contrast the specimens examined.
What if you were presented with just one of these species. How would you
know if it was a copepod, isopod, etc.?
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Part two.
Terrestrial arthropods
Pillbugs
Examine the pill bugs or land isopods available. There are about three species of
varying size and color that are living happily together in an aquarium. All are US
natives.
Compare its morphology to the fresh water amphipod or isopod that you
observed.
Compare how it uses its legs to walk with how the fresh water amphipod
used its limbs to swim?
Millipedes
Obtain a millipede. Make sure you record whether you are working with Sigmoria
aberrans (black with yellow or pink on edges) or Narceus americana (longer
than Sigmoria and uniform in coloration).
Count the number of legs found per segment.
Observe and record if you can locomotion in the millipede. How much of
the body moves as a unit when moving forward? When turning?
Transfer your millipede to a sand surface (sand is bumpy and so you will
be able to see leg movement better). What type of tracks would left by the
moving millipede? Are they impressions of appendages on or body
segments dragged through the sand?
d. Which of the following tracks would they most resemble?
Millipede track one
Millipede track two
Draw as best you can in Photoshop or use your smart phone to “record”
leg movement.
Photoshop instructions: You can simply ask for a new file, specifying one about
6 by 6 inches. Then use a small sized paintbrush in any color you wish to draw
your impression of the tracks that would be left behind by a millipede.
See example below.
Groups choosing different species should compare their results.
Centipedes
Obtain a petri dish containing a centipede. Compare its morphology with that of the
millipede. Do not open the petri dish. You may obtain a photograph of the
centipede to label or simply photograph the poison gland (we have slides).
Centipedes are voracious predators as opposed to millipedes who eat decaying
plant material for the most part.
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INSECTS
Insects are the most successful land group.
Compare the tagmatization found in insects to that of the shrimp you
photographed last week. Also compare the tagmatization found in insects to
that of millipedes and crustaceans.
You are to observe "walking" in an insect. Which legs move together?
Compare its movements to that of the pill bug and millipede.
Everyone should view termites and springtails and then choose one other
insect to examine.
Description of Springtails or Collembola.
Not quite insects!! Although considered hexapods (having six legs), why are
these not considered true insects? It is because their mouthparts are not
free as in most insects. Go ahead and examine the head on high power
and compare the head of a springtail to that of a termite or true insect of
about the same size.
Obtain a photograph of the springtail and termite. Label antennae, head and abdomen
in both species. Describe which body structure contains the legs. The
springtails are in petri dishes and so will not “jump” or use their furcula. To see
this structure, please view one of the slides we have available of Collembola.
The name Collembola, derived from the Greek "coll" meaning glue and "embol"
meaning a wedge, refers to a peg-shaped structure, the collophore, on the
underside of the first abdominal segment. The collophore was once thought to
function as an adhesive organ, now is thought to play a role in osmoregulation.
These were once considered insects, now placed in a separate group under the
Hexapoda, a group that also contains the insects. They are also known as
springtails because of their forked jumping organ (the furcula) found on the
fourth abdominal segment.
.
Termites are true insects. They are social and many species have castes, or
individuals that differ in morphology and their role in termite society. You should
have some workers and perhaps a soldier (larger, larger head and jaws) in your
petri dish. Take a photograph of your termite and label as many body parts as
you can. I could not find a labeled diagram of a termite for you, so the
grasshopper diagram will have to suffice for common structures found in most
insects.
Choose one of the following species to examine. Compare locomotion and
tagmatization in one of these species to that of the termite.
Bessbugs
These harmless beetles live in and under moist, rotting wood. Bessbugs are paternal
and adults will chew up wood and feed it to the young larvae. A common species is
Odontotaenius disjunctus but our supplier does not identify their cultures. Adults
stridulate by rubbing abdomen against the wings. Larvae stridulate with reduced third
pair of legs–these scratch against other legs.” We only have a few of these but they
should walk on wet dirt in a large dish for you.
Ladybugs.
In spite of their common name, ladybugs are not bugs (insects in the order Hemiptera)
and are instead beetles (order Coleoptera) in the family Coccinellidae over 500 in the
US Surprisely these colorful insects are voracious predators. Both adults and larvae
feed on aphids and sometimes other small insects. These is an organization
dedicated to their conservation. http://lostladybug.org/
These are a great choice because they can be examined in detail under the
stereoscope and readily move. They unlike the bessbugs do not appear to hide when
disturbed.
Darkling Beetles. We have larvae of some larvae. Darkling beetles. Cultures tend to
synchronize their development and so all our larvae are the same size and almost of
the size that pupates. Newly hatched larvae are almost microscopic and may molt 50
times or mo re before reaching pupation size.
560 × 373 - bugguide.net
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Arachnids
The slide of the pseudo scorpion is our only representative of the group Arachnida.
Compare its tagmata to that found in insects and crustaceans. Verify your examination
by obtaining a labeled photograph for your journal
.
We have other slides if you are interested. For example, we have slides of
centipede’s poison gland and Limulus blood. Watch your time. You should allow
about 45 minutes to complete and edit your journal before turning the thumbdrive over
to Ms. Hassell. Make sure all your files on the drive and your videos are clearly
labeled. She cannot grade what she cannot find. It is your responsibility and not hers
to make sure your material is clearly labeled and easy to locate. It is also your
responsibility to make sure she can easily determine which video goes with which
photograph or other information found in your journal. Your journal should be in the
format of a Microsoft word doc.