1. The Fishes Vertebrate Success in Water

2. Evolutionary Perspective Primitive Fishes can be traced back 530 million years ago Hagfish are the most primitive fishes known Aquatic environments have selected for certain adaptations including streamlining for moving thru a dense medium Ability to exchange gases with water or air Regulating buoyancy and electrolytes and detecting environmental changes

3. Infraphylum Hyperotreti Hagfish are divided into 20 species Heads supported by cartilage bars and brains enclosed by a fibrous sheath They lack vertebrae but retain a notochord as the axial supportive structure Four pairs of sensory tentacles surround the mouth Ventrolateral slime glands produce copious amounts of slime They feed on invertebrates and dead fish

4. Hagfish

5. Hagfish Mouth

6. Hagfish Slime

7. Infraphylum Vertebrata Ostracoderms are extinct agnathans Sluggish swimmers, Had bony armor as their only defense Bottom dwellers, filter feeders either filtering water or muddy sediment Some ostracoderms used bony plates around the mouth as jaws to crack mollusc shells or arthropod exoskeletons

8. Ostracoderms

9. Lampreys Agnathans (jawless) Fish who live in fresh and marine environments in temperate regions Most adult lampreys prey on other fish, larva are filter feeders Mouth is sucker like with lips used for attaching Epidermal teeth line the mouth and tongue like structure Attach to prey with teeth and lips, tongue rasps away scales Anticoagulant produced in saliva, feeds on blood

10. Lamprey

11. Lamprey Mouth

12. Lamprey

13. Gnathstome, Jawed Vertebrates Jaws evolved from the anterior pair of gill arches Permitted more efficient gill ventilation Allowed the capture and ingestion of more food sources Streamlining and paired fins became more important with increased activity Paired pectoral and pelvic fins reduced the tendency to roll during swimming

14. Class Chondricthyes Cartilage skeleton fish, includes sharks, rays, skates and ratfishes (chimeras) Most are carnivores and scavengers, most are marine Placoid scales Elasmobranch subclass (820 species) sharks, rays, skates started in early Devonian 375 mya Tough skin with placoid scales pointing posteriorly aids in reducing friction

15. Chondricthyes

16. Basking Shark

17. Sting Ray

18. HammerHead

19. Skate

20. Great White

21. Rat Fish

22. Shark Feeding Shark teeth are modified placoid scales The row of teeth on the outer edge is backed up by rows of teeth attached to a ligamentous band As the outer teeth wear or break off, they are replaced Replacement is rapid, 7-8 days Teeth may be adapted for shearing flesh, Top teeth cut while bottom teeth hold Teeth may be modified for breaking shells of molluscs

23. Placoid Scales

24. Shark Senses Ampullae of Lorenzini- Sensory pits on snout of sharks, able to detect very small electrical charges, heart beating, nerve impulse Lateral line- detects vibrations in the water, any movement or change in water pressure around the shark Nostrils- widely spaced on both sides of head, nostril is u shaped, not used for breathing Eye sight- Excellent, dark eyes to absorb maximum light, nictitating membrane cover

25. Ampullae of Lorenzini

26. Ampullae of Lorenzini Structure

27. Lateral Line

28. Lateral Line System

29. Nictitating Membrane

30. Rays, Skates and Ratfish Rays and Skates are specialized for living on the ocean floor by expanding the pectoral fins Some have venomous spine at base of tail used for defense Many have camoflaged their dorsal surface to blend in with the bottom Ratfish have a single gill cover (operculum) an enlarged head with teeth shaped for crushing shells

31. Sting Ray Barb