Class Chondrichthyes

1. Class Chondrichthyes 1

2. Class Chondrichthyes • 846 species of sharks and rays • Date to over 400 mya • Cartilaginous endoskeleton • Jawed • Well-developed pectoral/pelvic fins, powerful tail fin • Skin is rough due to numerous placoid scales (constantly worn out/replaced) 2

3. Class Chondrichthyes • Teeth = enlarged placoid scales • Teeth form in actively growing skin areas in mouth just behind upper/lower jaws; skin grows, teeth pushed over edge of jaw and increase in size • Teeth worn = reabsorbed or lost • In rays, teeth fuse to form bony plates 3

4. Class Chondrichthyes • Internal fertilization facilitated via unique pelvic claspers on males • Anamniote eggs encapsulated in leathery case or retained in body until birth of living young 4

5. Class Chondrichthyes • 2 informal groups: differ in body plan and dentition 1. Sharks (359 species) • powerful swimmers • mid-water dwelling • solitary predators 2. Rays (456 species) • dorsoventrally flattened, enlarged pectoral fins--subject to waves of muscular contraction • bottom-dwelling • eat shelled inverts (crush) 5

6. Class Chondrichthyes • Most marine, some taxa are estuarine or freshwater (28 species) • Range in size (from 20 cm to over 12 m) • Commercially important in food,cosmetic,pharmaceutical, and medical products • Estimated 771,400 tons of sharks/rays harvested each year by humans (while only 30 humans-2.6 tons harvested by sharks) 6

7. Class ChondrichthyesSubclass Elasmobranchii • Cartilage skeleton • Notochord • No opercula • No swim bladder 7

8. SqualusDogfish Shark 8

9. DasyatusStingray 9

10. Superclass Osteichthyes

11. Class Actinopterygii • Rays in fins • Bones • Operculum • Swim bladder

12. Class Actinopterygii • Ray-finned fishes • Most bony fishes and largest single group of chordates (24,000 species) • Well-adapted; successful in marine and freshwater • Carnivores, herbivores, parasites, and scavengers

13. Features • Acrodin-covered teeth • Circulation • 2-chambered heart • Blood flow under low pressure • Blood flows in opposite direction as water in gills, which maximizes oxygen saturation • Brain • Sensory and to some extent motor coordinating centers well developed • Overall coordinating and reasoning centers are primitive

15. Fish Scales

17. Examples • Primitive: heavy scales, use swim bladder for respiration in stagnant waters • Bichir - freshwater Africa • Gar - Kansas • Paddlefish - N. Am. • Sturgeon - N. Am. • Bowfin - N. Am.

18. Examples • Derived: Dominant fishes today; extremely diverse (morphology); upper jaw protrusible, thin/flexible scales, swim bladder for buoyancy • Herring (predator) • Coral reef fish (lateral compression) • Flounder (very laterally compressed, swim on side, eyes on upper body) • Moray eel (tubular, sacrifice speed for agility)

19. Adipose Fin Dorsal Fin Pelvic Fin Caudal Fin Pectoral Fin Anal Fin Salmon

20. Class Dipnoi • Lobe-finned fishes • Reduced skeleton • Teeth modified into plates (enamel) • Intracranial joint is immobile • Swim bladder highly vascularized and used as a lung

21. Subclass DipneustiLung Fish • Breathe air when lake or river dries up

22. Lungfishes • 6 species of freshwater lungfishes found in tropical regions of Africa, Australia, and S. America • Areas subject to drought • Some use lungs when conditions unfavorable, use gills otherwise • In others, gills reduced and dependent on lungs

23. African Lungfish • Burrows in mud when water dries up • Secretes a mucous cocoon around its body with air hole at tip • Can survive up to 4 years

24. Gas exchange • Gills • Skin • Mouth • Gulp air • Lungs

26. Buoyancy • Sharks must constantly swim to keep from sinking

28. 1% Salt

29. Salt Absorb Salt Urine Freshwater Fish 0% Salt Water 1% Salt

30. Salt Secrete Salt Urine Marine Fish 3.5% Salt Water 1% Salt

31. Reproduction • Lay eggs in water • Ovoviparous • Egg remains in mother until offspring hatch • The offspring are born alive • Viviparous • Embryo receives nourishment from mother • The offspring are born alive

32. Courtship Behavior

33. Longnose GarOrder SemionotiformesLepisosteus • Ganoid scale • Long snout

34. Channel CatfishOrder SiluriformesIctalurus • Rounded anal fin

35. Large Mouth BassOrder PerciformesMicropterus • Large mouth • Upper jaw extends past the eye

36. Small Mouth BassOrder PerciformesMicropterus • Small mouth

37. CrappiesOrder PerciformesPomoxis • White crappie is not as dark as dark as the black crappie • Eat crustacean and small fish

38. Bluegill SunfishOrder PerciformesLepomis • Small mouth • Oval shape • Eat crustaceans and insects

39. CarpOrder Cypriniformes • Large dorsal fin • Arched back • Omnivores

40. Tetrapods • Animals with 4 limbs • Amphibians • Reptiles • Birds • Mammals • Evolved from fish

41. Transition from Sea to Land

42. Class Sarcopterygii • Coelacanth • Lobed fins • muscles Order Crossopterygii

43. Class Actinistia • Only one marine species remains in this ancient lineage • Lobe-finned fish called a coelacanth • Only living chordate with a movable intracranial joint • divides skull into anterior and posterior halves • may allow upper jaw to elevate • Fatty swim bladder (some buoyancy) • Predator • Enamel-covered teeth

44. Coelacanth

45. Coelacanth • Thought to have been extinct until discovery in Indian Ocean in 1938 • Since then, recovered 70+ • Live in underwater lava caves at depths of 200-300 meters • Compared to fossil evidence, not many changes-habitat stable (molecular level unknown)

47. Tetrapod Ancestors • Response to periodic drying or to avoid predation/competition in aquatic habitat • Limbs further developed as stayed on land • Few competitors, no predators—selective pressure in favor of the land move • 2 features: • Functional lungs (as well as gills) • Fleshy lateral fins containing muscle to support body and provide mobility

48. Tetrapod Ancestors • Skeletal bones in fins similar to bones of primitive tetrapods • Limbs thought to have developed in the water, not on land

49. Eusthenopteron

50. Panderichthys