ZOO 137 - Invertebrate Zoology Phylum Info File -- Arthropoda
and Onychophora

Kingdom Animalia - Subkingdom Metazoa

Phylum Onychophora (etymology: ___________________________________________)

Phylum Arthropoda (etymology: _____________________________________________)

Subphylum Trilobita (etymology: ___________________________________________)

Subphylum Chelicerata (etymology: ________________________________________)

Class Merostomata (etymology: ______________________________________)
(examples: ________________________________________________)

Class Arachnida (etymology: ________________________________________)
(examples: ________________________________________________)

Subphylum Crustacea (etymology: _________________________________________)
(examples: ________________________________________________)

Subphylum Uniramia (etymology: __________________________________________)

Class Diplopoda (etymology: ________________________________________)
(examples: ________________________________________________)

Class Chilopoda (etymology: ________________________________________)
(examples: ________________________________________________)

Class Insecta (etymology: ___________________________________________)
(examples: ________________________________________________)

Note that the classification above is somewhat different than that in the PAZ. You will need to know the one given above.

Things You Should Do Before Coming to the First Lab on Arthropods

o Memorize the classification given above.
o Study Chapters 17-19 and 20 (pp. 457-460) in Animals Without Backbones (note that there are many drawings and photographs that will help you interpret the material you see in the lab)
o Complete exercises 38-39, 41-48 and 50 in The Zoology Coloring Book (optional but highly recommended; check the highlight sheets in lab for certain parts you do not need to color).
o Pack your dissecting kit; you'll need it for the both arthropod labs.

Things You Should Do During the Labs

We will devote two lab periods to the arthropods. This is the largest phylum of animals, so expect a lot of new information. For convenience, we will divide the phylum into two study sessions: one focussing on the crustaceans and chelicerates, the other on insects and myriapods. During quarters when time permits, these labs will be followed by one devoted to a seminar on social insects.

Lab Period One (Monday): Crustaceans and chelicerates

o Observe the external structure and dissect a specimen of the crayfish, Cambarus, using Figs. 9.11 - 9.16 as your guide (ZCB plates 42-43 will also be helpful). Know and be able to use all terms in the PAZ figures except the following: 9.11 (tergum and pleuron); 9.12 (no. 12); 9.13 (nos. 2-4, know only that they are maxillipeds; note that guidelines labeled 1 and 2 on the right should read 5 and 6); 9.14 (nos. 4 and 6); 9.15 (4 and 13-15); and 9.16 (no exclusions). None of these figures points out the heart; be sure you observe it nonetheless. Open your specimen by carefully peeling off the carapace and dorsal surface of the first few abdominal segments; don't bother to use a scalpel - it won't work. Notice that the carapace extends as a flap than covers and protects the gills attached to the bases of the legs. As a part of your dissection, remove the appendages from one side of the animal and lay them out in correct order; they will illustrate one of the important features of this phylum: division of labor among the pairs of segmental appendages. There are 19 pair, as follows: two pair of antennae, six pairs of mouthparts (feeding appendages -- mandibles, 2 pair maxillae and 3 pair maxillipeds), five pair of legs (the first three have apical pincers), five pair of swimmerets (although they're not used for swimming! The first two pair are modified in the male for sperm transfer), and a pair of uropods (which, along with the single telson, are used as paddles). Ask for assistance in removing the mouthparts as the maxillae, in particular, are very small and easy to tear. Index cards and glue will be available if you want to paste them out as a study aid.

o Examine the model of the crayfish. The correspondence between the model and real crayfish is quite close. You'll see the model as well as dissections on the lab practical.

o Examine the external morphology (only) of each of the following two chelicerates (specimens will be available in the dissection cart; return them to the containers after you're done.):

-- The horseshoe crab, Limulus (not really a true crab at all). Know all the structures indicated in PAZ Fig. 9.2 except nos. 9, 14-15). Be careful handling this creature; the spines along the sides of the abdomen are sharp!

-- The golden garden spider, Argiope, a common spider on the campus. Know only the following structures in PAZ Fig. 9.3: fang, chelicera, pedipalp, eyes, legs, book lung slit, spinneretts, cephalothorax (= prosoma) and abdomen (= opisthosoma).

o Examine the following demonstration specimens:

-- Various types of crustaceans; you do not need to memorize their different names; know that they are crustaceans, however.
-- Specimens of the following kinds of arachnids, which you do need to know: ticks, scorpions, and whip scorpions (not really true scorpions).
-- Fossils of the long extinct subphylum of arthropods known as trilobites.

Lab Period Two (Wednesday): Myriapods and insects

o Observe the external structure and dissect under water a specimen of Romalea, the lubber grasshopper. Open your specimen along the dorsal midline. Use PAZ Figs. 9.26-9.28 as your guide. ZCB plates 46-48 will also be very helpful. Know all terms in the PAZ figures except the following: 9.26 (nos. 3, 5-6, 8, 10-12, 16-18); 9.27 (vertex, gena, frons, and palps); 9.28 (no exclusions). Note that to observe the tracheae, you will need to view the specimen under water with a dissecting microscope. Ask for assistance if you have trouble. Make sure you see both male and female, which differ in the structure of their external genitalia. In the female, they form an egg-laying structure called an ovipositor. As a part of your dissection, as you did for the crayfish, remove the appendages of the head and thorax from one side of the body. There will be eight: one pair of antennae, four pair of mouthparts (ask for assistance in removing these), and three pairs of legs (note the difference between the last and first two pairs). The wings, because thay are not segmented like the legs, are not considered true body appendages; there are two pair of them, which are small and non-functional in this flightless grasshopper.

o Examine the models of the grasshopper. There are two of them, both of a female and both showing the same structures. The structures will correlate well with those you observe in the dissection.

o Examine the following demonstration specimens and slides:

-- A slide showing a spiracle and attached tracheae of an insect. The spiracle (opening) is the dark, bean-shaped portion; the tracheae (tubes) have been cut off to fit on the slide.
-- Centipede specimens. Centipedes are one of the two myriapod groups. Know the class characteristics.
-- Millipede specimens. Millipedes are the other myriapod group. Know the class characteristics.
-- There will be several drawers of insect specimens, mostly showy tropical species. You do not need to know all these; they're out to give you an idea of just how diverse the insects are.
-- Specimens illustrating the two major kinds of insect development: holometabolous development (also called complete metamorphosis) and paurometabolous development (a.k.a. gradual metamorphosis). The fundamental difference between the two is the degree of difference in morphology between larva and adult. In complete metamorphosis, they are so different that a special stage (the pupa) is needed to bridge the gap between adult and larva.
-- Specimens of Peripatus, the "velvet worm." This caterpillar-like animal is not an arthropod at all, but a member of the phylum Onychophora, which has characteristics that link it with both the annelids and the arthropods (see the specimen card). Know its genus and phylum names as well as the features it shares with annelids and arthropods.

Things You Should Do After the Lab

o Using all sources available to you, make a list of ten important features, characteristics, etc. of the arthropods -- don't overlook segmentation and tagmata, segmented appendages, hemocoel, and exoskeleton.

o Be sure to correlate what you've observed in lab with your readings and lecture notes.