1. Bellwork: 02/12/2014 – Don’t start water changes yet
What is the defining characteristic of Chondrichthyes?
What are the two subclasses & give examples of each:

2. Bellwork: 02/20/2013 - Continued
What is the name of the body form of sharks?
When did the radiation of chondrichthyes begin? What is the earliest period that scientists have found scales of chondrichthyes?

3. Bellwork: 02/12/2014 Change the water on your tank.
Please scrub the glass & check the filters.
Clean of the glass lids as well
Class Chondrichthyes

4. Sharks, Skates, Rays and Chimeras
Class Chondrichthyes
Class Chondrichthyes

5. Class Chondrichthyes Subclass Elasmobranchii Subclass Holocephali
Sharks
Skates and Rays
Subclass Holocephali
Chimaeras (Ratfish)
Traits
Habitats
Class Chondrichthyes
Class Chondrichthyes

6. Bellwork: List 3 differences between skates & rays:
Which organ is responsible for the buoyancy of many chondrichthyes?
List & describe respiration methods in chondrichthyes:
Class Chondrichthyes

7. Class Chondrichthyes - Rays
Subclass Elasmobranchii
Thin, flexible, and barbed tails
Can be extremely large (25 feet across, weighing several tons)
Serrated spines that are very difficult to remove from victim
Spines are covered with a thin skin that contains painful toxins once ruptured
Predominantly live-bearers
Class Chondrichthyes
Class Chondrichthyes

8. Class Chondrichthyes - Skates
Subclass Elasmobranchii
Fleshy, heavy tails
Relatively small (1 to 5 feet)
Elongated nose
Often found in North America
Large thorns for defense, but not poisonous
Lay eggs (mermaid’s purse)
Class Chondrichthyes
Class Chondrichthyes

9. Class Chondrichthyes - Chimeras
Subclass Holocephali
Possess cartilaginous skeleton, intromittent organs, spiral valve intestine, and oil filled liver
Single gill slit, no scales
Only have 6 permanent teeth for grinding
As a group found mostly between 80-2,600 meters, feeding on hard shelled invertebrates
Class Chondrichthyes
Class Chondrichthyes

10. Chondrichthyes Life History
Strategy of Sharks & Rays
Produce precocial (well developed at birth) young with high survival rates
Slow growing, long lived, and reach sexual maturity at a late age (13 to 19 years)
Class Chondrichthyes
Class Chondrichthyes

11. Adaptations Buoyancy Respiration External covering Feeding Movement
Sensory systems
Class Chondrichthyes
Class Chondrichthyes

12. Buoyancy Huge oil-filled liver Lift created by a heterocercal tail
A shark that has an air weight of 1,000 kg. weighs only 3.3kg in water
Lift created by a heterocercal tail
Class Chondrichthyes
Class Chondrichthyes

13. Caudal Fin Types Homocercal – two symmetrical lobes
Class Chondrichthyes
Class Chondrichthyes

14. Caudal Fin Types Heterocercal – much larger dorsal lobe
Class Chondrichthyes
Class Chondrichthyes

15. Respiration Chondrichthyes employ 3 different methods of respiration
“Two pump” method
Ram ventilation
Spiracles
Class Chondrichthyes
Class Chondrichthyes

16. Class Chondrichthyes

17. Respiration Chondrichthyes employ 3 different methods of respiration
“Two pump” method
Ram ventilation – species swims with mouth open
Spiracles
Class Chondrichthyes
Class Chondrichthyes

18. Respiration Chondrichthyes employ 3 different methods of respiration
“Two pump” method
Ram ventilation – species swims with mouth open
Spiracles – small holes behind each eye that opens to the mouth in
Class Chondrichthyes
Class Chondrichthyes

19. Respiration
Spiracles – small holes behind each eye that opens to the mouth.
This allows water to be drawn in from above the organism
Class Chondrichthyes
Class Chondrichthyes

20. Spiracle
Class Chondrichthyes

21. External Covering
All Chondrichthyes have placoid scales in one form or another
Placoid scale modifications
Spine of stingray, dorsal spine of dogfish, defensive spines in the skate, and teeth
Class Chondrichthyes
Class Chondrichthyes

22. External Covering Sting Ray Barb: Class Chondrichthyes

23. External Covering Dogfish Spine Class Chondrichthyes

24. Feeding
Most are specialized predators and have dentition that reflects their lifestyle
Sharks that prey on fish and marine mammals have triangular blade-like teeth
Used for grabbing and tearing
Can exert biting pressures of 2,800 kg/cm3
Teeth are constantly being shed and replaced
Up to 30,000 in a lifetime
Class Chondrichthyes
Class Chondrichthyes

25. Class Chondrichthyes

26. Feeding Digestion Spiral valve Class Chondrichthyes

27. Circulatory Pelagic sharks have rete mirabile (“wonderful net”)
Blood flows both ways in capillaries.
Arteries & veins are very close to each other .
Class Chondrichthyes
Class Chondrichthyes

28. Circulatory
This lowers blood pH allowing oxygen to unbind from hemoglobin & increase the overall oxygen saturation in the blood.
Allows thermoregulation, faster ATP breakdown, and ultimately faster swimming .
Class Chondrichthyes
Class Chondrichthyes

29. Circulatory .
Class Chondrichthyes
Class Chondrichthyes

30. Sensory Systems
Sharks have well-developed sensory system which acts in concert to locate prey and find their way around the environment
Some species can detect a drop of blood as dilute as 1 part per billion
Also, very good at following an odor trail
Class Chondrichthyes
Class Chondrichthyes

31. Sensory Systems Hearing Olfaction Lateral line Class Chondrichthyes

32. Sensory Systems
Class Chondrichthyes
Class Chondrichthyes

33. Sensory Systems
Visual systems are well developed for use during night and day
Tapetum lucidum = increased vision at night
Nictitating membrane
Class Chondrichthyes
Class Chondrichthyes

34. Sensory Systems
Visual systems are well developed for use during night and day
Tapetum lucidum = increased vision at night
Nictitating membrane
Class Chondrichthyes
Class Chondrichthyes

35. Sensory Systems Nictitating membrane – transparent 3rd eyelid
Class Chondrichthyes
Class Chondrichthyes

36. Sensory Systems
Class Chondrichthyes

37. Sensory Systems
Class Chondrichthyes

38. Sensory Systems
Class Chondrichthyes

39. Sensory Systems
Class Chondrichthyes

40. Sensory Systems
Class Chondrichthyes

41. Sensory Systems
Class Chondrichthyes

42. Sensory Systems
Ampullae of Lorenzini – electroreceptors (sense biological electric fields)
Tonic Immobility
Tonic Immobility #2
Class Chondrichthyes
Class Chondrichthyes

43. Ampullae of Lorenzini
Class Chondrichthyes
Class Chondrichthyes

44. Class Chondrichthyes

45. Chondrichthyes Reproduction
Most species have extended gestation periods in egg cases or in the body cavities of females
Young traits
Internal fertilization, through the use of claspers on the male
Class Chondrichthyes
Class Chondrichthyes

46. Chondrichthyes Reproduction
Oviparity – lays eggs (little or no embryonic development within the mother)
Viviparity – internal development
Yolk-sac Viviparity
Uterine Viviparity
Cannibal Viviparity
Placental Viviparity
Class Chondrichthyes
Class Chondrichthyes

47. Oviparity - Egg Laying Oviparity Class Chondrichthyes

48. Oviparity - Egg Laying Oviparity Class Chondrichthyes

49. Viviparity Yolk-sac Viviparity (Ovoviviparity) Uterine Viviparity
Eggs are produced and retained inside the mother
Shell disappears and young are retained until fully developed
Uterine Viviparity
Mother secretes nutrient rich fluid which is taken up through the skin of the embryo
Class Chondrichthyes
Class Chondrichthyes

50. Viviparity Yolk-sac Viviparity (Ovoviviparity) Class Chondrichthyes

51. Cannibal Viviparity/oophagy
Young in each oviduct consume unfertilized eggs or other siblings (Sand Tiger Sharks)
Class Chondrichthyes
Class Chondrichthyes

52. Cannibal Viviparity/oophagy
Class Chondrichthyes
Class Chondrichthyes

53. Placental Viviparity
Nutrients are supplied to the embryo directly from the mother via a umbilical cord
Class Chondrichthyes
Class Chondrichthyes

54. Class Chondrichthyes

55. In groups of two/three:
Angel Shark River Stingray
Wobbegong Shark
Blacktip Reef Shark American Round
Bull Shark Stingray
Goblin Shark Electric Ray
Great White Shark Bottlenose Skate
Hammerhead Shark Manta Ray
Mako Shark Whip-tail sting Ray
Nurse Shark Ghost Shark/elephant shark
Whale Shark Ratfish (not rattail)
Tiger Shark Giant Stingray