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Class Chondrichthyes

Class Chondrichthyes. 1. 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.

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Class Chondrichthyes

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  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

  14. Fish Scales

  15. 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.

  16. 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)

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

  18. 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

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

  20. 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

  21. 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

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

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

  24. 1% Salt

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

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

  27. 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

  28. Courtship Behavior

  29. Longnose GarOrder SemionotiformesLepisosteus • Ganoid scale • Long snout

  30. Channel CatfishOrder SiluriformesIctalurus • Rounded anal fin

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

  32. Small Mouth BassOrder PerciformesMicropterus • Small mouth

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

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

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

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

  37. Transition from Sea to Land

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

  39. 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

  40. Coelacanth

  41. 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)

  42. 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

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

  44. Eusthenopteron

  45. Panderichthys

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