Lab 9: Tardigrada, OEB 51 Lab 9: Tardigrada, Onychophora, HMNH

13 April 2016

HMNH Exhibit on Diversity

For segment of the lab, we will take advantage of the side-by-side layout and the enormous arthropod diversity presented here. As you explore the exhibit, consider the following questions – which will also be useful as a review/study guide for the final exam. Discuss in small groups.

• In what ways is the wall phylogeny of the arthropods in strong or potential disagreement with our current understanding of arthropod relationships?

• Describe the tagmosis of the arthropod clades – i.e., into how many regions is the body divided, and what is the name and major function of each in this clade? For , you choose a decapod as your “idealized” form.

1 Lab 9: Tardigrada, Onychophora OEB 51

• Which of the major arthropod clades are well adapted to land, and how do they differ in their adaptations to terrestriality with respect to aquatic ones? Consider respiratory, locomotory and excretory systems. Are there groups that were more successful on land than others? Why?

• Distinguish between biramous and uniramous limbs in theoretical terms, and give specific real examples of each. What, functionally, is the utility of a biramous ? Why do few terrestrial arthropods possess biramous ?

2 Lab 9: Tardigrada, Onychophora OEB 51

• Compare the anterior segments of the major arthropod groups and explain their . Also describe the relationship between the three anterior-most pairs of ganglia and the appendages they innervate in each group.

• Briefly describe in terms of the physiological and the physical processes. Draw a cross section of a indicating the major layers.

• How is growth in an organism with ecdysis? Is it a continuous process?

3 Lab 9: Tardigrada, Onychophora OEB 51 Tardigrada Water bears are divided in to two main groups: Eutardigrada and Heterotardigrada. Today we have live specimens of both groups! (Courtesy of Dennis Persson, postdoc at the Giribet Lab) Choose one species and start by looking at them moving under the dissecting scope. Then pipette CHOOSE ONE one specimen out and make a wet mount to look closer at its (clay feet not necessary, but might help to change the position of the ).

• Echiniscus testudo, an orange Heterotardigrade • dujardini, a transparent Eutardigrade

Make an illustration of the entire animal, showing the regionalization of the gut, the position of the mouth and , and whatever internal anatomy is visible. Use the 100x with immersion oil (ask for it) to get a good view of the oral stylet and the , and draw. Exchange slides with a classmate to take a quick look at differences between the two groups.

4 Lab 9: Tardigrada, Onychophora OEB 51 Onychophora We have several preserved specimens of Onychophora from both the and the family . One of these families has body insoluble in ethanol – can you guess which? CHOOSE ONE

Choose one species and draw the external morphology. Orient the specimen to get a good ventral view of the , and distinguish the antennae, the slime-spitting oral papillae, the and the first pair of . What are the openings in the posterior end?

• Austroperipatus (Peripatopsidae) • novaezealandiae (Peripatopsidae) • isthmicola (Peripatidae)