1. Welcome to shark week

2. ?

3. Shark Dissection Prelab: What’s the scientific name for the spiny dogfish?
Squalus acanthias

4. What family do you think it is in?
Squalidae
“Squalus” is Latin for
“a kind of sea fish.”
Isn’t that imaginative!?!

5. 1. What’s the overall body shape?
Torpedo-shaped
Fusiform: tapered at both ends, reduces drag
Adapted for fast swimming

6. 2. What’s with the coloration?
Counter-shading: double camouflage

7. 3. What are the three body divisions?
Head:
From tip of snout to caudal edge of the gill slits
Tail:
From the cloaca to the tip of the caudal fin
Trunk:
…to the ventral opening of the cloaca

8. 4. What’s that horozontal strip and what does it do?
Lateral line

9. It senses pressure differences in the surrounding water (we don’t experience this at all)

10. 5. Note: this is NOT a dogfish shark.

11. 6.
Good guess: they are called SPINES

12. Spines on an adult (yes they are slightly poisonous)

13. 7. How do you describe this tail?
Upper lobe of caudal fin longer than lower lobe: Heterocercal
Here is an extremely HETEROCERCAL TAIL in the thresher shark

14. 8. Rostrum: the pointed snout at the anterior end.

15. We’ll pause here for now and get to know our specimens

16. 9. How are shark eyes similar & different to mammal eyes?

17. Similar: same overall structure and same tissues
Similar: same overall structure and same tissues. Different: no eyelid, and differently shaped lens.

18. 10.

19. 11. Like most sharks, the dogfish has 5 gill slits
The exception is the primitive 6 gill shark

20. 12.
Pectoral fins provide lift, just like wings on a plane

21. 13. Pelvic fins

22. 14. Shark teeth

23. Uniform shape, lined up in rows, set in gums rather than in jaw-bone

24. 15. nostrils

25. 16.
Ampullae of Lorenzini. These sense organs are sensitive to changes in temperature, water pressure, electrical fields, and salinity.

26. 17.

27. 18. Draw a pair of denticles: