Ichthyology Fall 2007 Question Set 5

FEEDING STRUCTURES & DIGESTION Locate the following jaw structures in your teleost fish: premaxillary bone, maxillary bone, and mandible (dentary bone). 1. What do the modifications of these bones enable the more derived bony fishes to do better than the elasmobranchs?

Cut away the lower half of the mouth of your fish. Compare the morphology of the teeth and gill rakers among all the fishes. Note if they have teeth located on the buccal, pharyngeal, jaw, or any combination of these. Compare the intestines and stomachs of all the fishes in lab. Herbivores should have poorly developed stomachs, but long intestines, while carnivores should have well developed stomachs and short intestines. 2. Does the morphology of stomach and intestines agree with what the teeth, gill rakers, and pharyngeal jaws suggest the fish are eating? Are there any identifiable organisms in your fish’s stomach support your conclusion?

3. Does your fish have pyloric caeca? What about other fish? Does this relate to what they eat?

Try to find the pancreas and gall bladder in your two specimens. (It may be difficult to see these organs in the teleost...but try!) 4. How do these organs assist in digestion?

Draw the digestive tract of the shark and of the teleost, from the esophagus to the excretion pore and point out the main structures. 5. How is the intestine of the teleost different from that of the elasmobranch?

Carefully cut open the ileum of the shark. 6. What do you suppose a spiral tissue valve would assist in?

Compare the liver size (in relation to the body size) of the shark to that of the teleost fish. 7. What are the functions of the liver in the two fishes?

Ichthyology Fall 2007

8. What additional organ in the teleost fish shares a similar function to that of the liver in the elasmobranchs?

The liver of many sharks produces and stores a hydrocarbon called squalene. 9. Why do you suppose it produces and contains this particular substance?

10. How would the size of a horn shark’s liver compare to a pelagic blue shark’s liver?

CIRCULATION 11. Where is the heart located in the two fishes?

12. Given this location, what organ(s) do you suppose the heart is closely associated with?

The heart of elasmobranchs and teleosts is four chambered. Its function is to supply pressure to move the blood in the circulatory system. 13. What is the major difference between the heart of the elasmobranchs and the teleost?

14. What are the major differences between a human’s heart and a fish’s heart?

One of the main functions of the spleen in sharks is to produce new blood cells. 15. Why is it possible, therefore, for people who have lost their spleens in an accident to lead normal lives?

REPRODUCTION 16. What sex is your fish? How could you tell?

Go around the room and compare males and females of teleosts, and of elasmobranchs. Draw and label the organs of males and females.

The sperm ducts and tubules which sperm flow through and develop in are derived from the kidney in elasmobranchs, but in teleost they arose from the testes. Note the testes and the pathway sperm take out of the body. Ichthyology Fall 2007

17. Through what openings do the gametes of elasmobranchs and teleosts leave the body?

18. Is it the same for both sexes of each fish type? In what way does it differ?

BUOYANCY A swim bladder that is connected to the gut in an adult fish is called physostomous. A swim bladder that is not connected directly to the gut is considered physoclistous. 19. What type of swim bladder does the elasmobranch specimen have?

20. What type does your teleost have?

SENSORY SYSTEMS With your shark specimen, make a ‘V’ shaped incision through the skin on the dorsal side of the snout where the ampullae of Lorenzini are present. Pull the skin flap and underlying tissue forward and examine its underside. 21. What is contained in the receptor pores? How might this aid signal reception?

Sharks have both a lateral line system and ampullae of Lorenzini. 22. What is the difference between the ampullae of Lorenzini and the lateral line system?

Make a deep cut just posterior to one of your shark’s nares. Look at the cut as if it was a cross section of the shark’s nare and see if you can make out the olfactory sac containing the olfactory lamellae. The lamellae are the folds of tissue that increase the surface area of the olfactory sac aiding in the detection of chemicals in the water. The extensiveness of the lamellae (number and size) is directly related to the level of importance smell is to the fish. 23. Would you think that this shark relies on smell as a major sense?