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 “
effective legs”. Your descriptions should include any tagmata you can
see.
All containers should be rinsed with spring water before organisms are placed in
them. Be careful to note if you are working with a saltwater or freshwater
species. So as not to contaminate cultures please discard your specimen
when you are done or place in main tank. If freshwater it will die but will
be eaten by a snail or some other detritus feeder.
1. Daphnia
Everyone should look at locomotion in Daphnia, the common water flea. a. These are
highly transparent organisms and you can easily compare their anatomy to
that of the Caprellid shrimp of last week. If you can obtain a photograph of
a Daphnia, label heart as well as antennae. B. Also note: Are any females
carrying eggs? Daphnia when crowded becomes pink to red as individuals
develop hemoglobin. Can you think of any reasons for this? Is there any
evidence that our cultures have individuals that have developed hemoglobin?
c. Obtain a movie of Daphnia movement. d. Your journal should also contain a
paragraph on how Daphnia uses its appendages to move. e. Compare the
way Daphnia moves to that of the Caprellid shrimp and glass shrimp in your
journal.
A reference diagram for Daphnia
Examine the isopods and one of the other aquatic crustaceans available.
2. 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.
3. You may choose between freshwater crayfish, freshwater amphipods, or
freshwater or saltwater copepods as your third crustacean in which to
examine locomotion. It would be good if each table choose a different
species and then you could compare locomotion in each. All species move
rather quickly.
Choices available
Freshwater or saltwater 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 mayl 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.
4. 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
5. Pillbugs
Examine the pill bugs or land isopods available. There are several 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?
6. 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 or use your smart phone to “record” leg
movement.
Microsoft word instructions: Use insert a shape (the one highlighted below is a
good one to use).
The size of any shape can be modified. Use blue circles to modify size, yellow to
modify angle and green to modify orientation.
Once you have a basic shape, copy and paste a number of strokes to indicate
“foot” movement.
See example below.
You can also do the same in preview by choosing blank page and then using a small
oval or line to indicate “steps” used by the millipede or simply draw leg movement
on a blank sheet of paper and give to your instructor to scan before the next lab.
Dr. Feaver will scan any paper that clearly identifies the author and has their
email address and lab section on that paper.
7. Centipedes
Obtain a slide showing the poison gland of a centipede. Contrast the head
outline with that of the millipede you examined.
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 darkling beetles and springtails and then choose
one other insect to examine.
8. 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 beetle. Label antennae, head and abdomen
in both species. Describe which body structure contains the legs. Springtails
will “walk” but also “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.
.
9/10. Darkling beetles and grasshoppers are true insect. You may use one or the
either to observe walking in a typical insect. Choose one of these as your
model organism.
10. Choose one of the following species to examine. Compare locomotion and
tagmatization in one of these other species to that of the grasshopper or
beetle. You do not have to remove the animals from their cages and can
just if you wish watch them move in their home aquaria
a. Darkling Beetles larvae. Cultures tend to synchronize their development and so all
our larvae are the same size and almost of the size that pupates. Please compare
adults to related species of desert beetles of no adults are present in our cultures.
Newly hatched larvae are almost microscopic and may molt 50 times or more before
reaching pupation size.
b. Domino roaches
Adults are beetle mimics, possibly of Anthia sp. tiger beetles. Nymphs tend to be more
roach like and to burrow during the day, These roaches feed primarily on dried
leaves, but love small bits of protein-based pet foods and fruit.
c. Desert darkling beetles.
Flightless beetles often seen trudging across trails and over sandy terrain. If bothered, the
beetle does a headstand, signaling that it's ready to squirt a noxious substance onto an
assailant. The spray is foul to the nose, and isn't dangerous to people.
d. 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.
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11. Arachnids : Please examine a slide of a pseudoscorpion or hair follicle mite.
a. Pseudo scorpions. Compare the tagmata of Pseudo scorpions to that found in
insects and crustaceans. Verify your examination by obtaining a labeled photograph
for your journal. Pseudo scorpions are predators feeding on ants, mites and small flies
among other small arthropods. Many species spin silk from a gland in their jaws to
make cocoons for mating, etc. They do have venom glands located within their palps.
.
b. Note the adaptations for a parasitic life cycle on mites found on humans primarily in
the hair follicles of eyelashes and eyebrows. Two species have been identified and we
have slides of Demodex folliculorum. The adult mites are only about .4 millimetres
long with an very elongated body. The mites can leave the follicles and walk around
on the skin at night. Almost all adults over the age of 17 carry them. It is only in rare
cases that the mites result in any skin eruptions.
The species that infects dogs however can result in serious disease (mange).
Compare the structure of the hair follicle mite in your journal to that of a free living
arachnid.
12. Parasitic insects:
If time permits, look at the slides of lice. My daughter came home with these a few
times from school. Lice are insects but modified structurally for their ectoparasitic
lifestyle. There are three species that infect humans, identified by structure and habitat,
hair, body or pubic area. Compare the structure of one of these species to those of
the eyebrow mite. Make sure in your journal you note the species that you examined.