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LABORATORY 3: JAWLESS FISHES AND CHONDRICHTHYES

Please come to lab prepared to examine the assigned specimens and be ready to answer questions about them.  You may already have answered some of the questions in anticipation of the lab.

By the end of this laboratory experience, student teams will be able to:

JAWLESS FISHES

1.  Look at the preserved hagfish.  In what way(s) is it obviously fish-like?  How is it different?

 

 

 

Detail of the hagfish mouth.

2.  Now, compare the hagfish with a lamprey.  What are the obvious similarities?

 

 

 

 

 

 

 

 

 

 

 

 

3.  Aside from size, what are the differences?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.  Look at the longitudinal sections of the lamprey head.  Find: gill pouches, pharynx, buccal cavity, keratinized teeth, vertebrae, cranium.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.  How does water flow through the respiratory system of the lamprey?  How does this system facilitate the lifestyle of the lamprey?

 

 

 

 

 

 

 

 

 

 

 

6.  Lampreys usually have larvae that develop in freshwater.  Examine a slide of an ammocetes larva.  How different (besides size) is the larval animal from the adult?

 

 

 

 

 

 

 

7.  Look at conodont elements on the electron microscope and on your dissecting microscope.  Be able to recognize the following types of elements.

8.  How are the conodont elements different from the teeth of lampreys?

 

 

 

 

9.  Examine models of extinct agnathans.  Be able to recognize each animal and the class to which it belongs.

 

 

Pteraspis

Rhyncholepis

Hemicyclaspis

 

 

CHONDRICHTHYES

 

1.  Study the external morphology of the dogfish shark (Squalus).  Find the dorsal fins, the caudal fin, anal fin, pectoral fin, and pelvic fins.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.  What aspect of the dorsal fin gives this animal the name, Spiny Dogfish?

 

 

 

 

 

 

 

 

 

3.  How many gill slits do you see on either side?

 

 

 

4.  Now, slide your fingers from head to tail and back.  Describe what you feel.

 

 

 

 

 

 

 

 

5.  Examine the neurocranium (=chondrocranium) of the dogfish.  What is it made of?

 

 

 

 

6.  Describe the jaws and arrangement of teeth.

 

 

 

 

 

 

 

 

 

 

7.  Look at other shark teeth and jaws?  How are they similar?  How are they different?

 

 

 

 

 

 

 

 

 

 

 

8.  Examine a placoid scale on a slide and describe it.  How is it like a tooth?

 

 

 

 

 

 

 

 

 

 

 

 

9.  Look at other preserved examples of the Chondrichthyes.  How have the bodies of skates and rays become modified?  In what ways do they resemble the dogfish?

 

Image from Animal Diversity Web.

 

 

 

10.  What is the main structure used in swimming for a shark?  A ray?

 

 

 

 

 

 

 

 

11.  Now, compare them to a Chimaera.  In what obvious ways are dogfish, and rays different from the chimaera?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12.  Compare the representative preserved chondrichthyes according to the following criteria.

Taxa

Tail

Scales

Anal fin

Dorsal fin

Pectoral fin

Pelvic fin

Barbels

Mouth

Spines

Gills

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


13.  You have models of extinct sharks. Be able to recognize them.

Cladoselache from http://vivaldi.zool.gu.se/

Xenacanthus (formerly Pleuracanthus) from http://www.geo.ucalgary.ca/

 

 

 

 

14. Now look at the models of extinct placoderms.  Be able to recognize them.

 

 

JRH & CAI:  Last revised: 01/16/2009