Chondrichthyes

1. Chondrichthyes An Overview

2. Chondrichthyes • Are jawed cartilaginous fish composed of sharks, skates, and rays • They have a skeleton made up of cartilage and do not have any bones • They have existed on earth for over 400 million years • They are mostly ectothermic – have body temperatures similar to the temperature of the water around them

3. Chondricthyes Organisms Sharks and Ratfishes Skates and Rays Skate( top) Ray (bottom) • Shark (top) Ratfish (bottom)

4. SHARKS, SKATES, AND RAYS • What do you know about them? • How have they been able to survive on Earth for so very long when so many other organisms have perished? • Are they more beneficial or more harmful to humans?

5. Sharks • These fishes have teeth-like scales called denticles. • Their mouth is usually located ventrally and they were the first fish to have paired fins (pectoral & pelvic fins) for more efficient swimming. • They have 5 to 7 gill slits per side and no swim bladder. • The largest shark, the whale shark is a plankton feeder.

6. Shark Adaptations for Survival http://www.pbs.org/wnet/nature/lessons/symbiotic-strategies/video-segments/1496/ http://www.youtube.com/watch?v=nmvc35pnCYE

7. SharkInternal Anatomy • No Bones

8. Shark External Anatomy

9. Fusiform Body Shape that reduces frictional drag

11. How a Shark Swims • http://www.youtube.com/watch?v=Itag3_mRc4w • How a shark maintains buoyancy • http://dsc.discovery.com/videos/the-ultimate-guide-to-sharks-how-sharks-swim.html

12. Denticles

13. Shark Senses • Sound • Smell • Sight • Electromagnetic Fields • Touch

14. Shark Hearing Sound Travels 5X faster in water than air and quite far. Sharks have inner ears but no outer ears. They are attracted most by low-pitched sounds. Sharks cannot make any noises, they have no vocal cords. Bursts of sound, like that made by injured fish are particularly attractive. This is also the sound made by humans splashing in the water.

15. Shark Sense of Smell • Will then help the shark to move closer to the prey. • Through its nares (nostrils), sharks can detect one part of blood in many millions of parts of water. (One part per million is equivalent to you taking one large mouthful of food compared to all the large mouthfuls you will take in a lifetime). • http://dsc.discovery.com/videos/ultimate-guide-the-sharks-shark-smell.html

16. Shark Breathe Through Openings Called Nares (nostrils)

17. Sharks Sense of Sight They can see extremely well in dim light. While bony fishes cannot dilate their irises, sharks can to allow more or less light to reach their retinas. Some sharks have a third eyelid called the “nictitating membrane” that can move to cover the eye completely to protect it during feeding. • http://dsc.discovery.com/videos/ultimate-guide-the-sharks-vibrations-and-shark-vision.html

18. Sharks Senses • http://www.youtube.com/watch?v=D78jCw7EQYk

19. Sharks Eye and Eyelids

20. Sharks Sense of Electromagnetic Fields Produced by the prey can be detected by sharks. The “Ampullae of Lorenzini”, electro-receptors, located on the snout of the shark, allows them to detect weak electrical currents produced by a prey's gill movement.

21. Sharks detect weak electromagnetic Fields using the Ampullae of Lorenzini

23. Shark Touch and Taste • Sharks can feel touch with their skin • Sharks can taste their prey with their tongue

25. Sharks Detect Vibrations and changes in water pressure with their Lateral line

26. How Sharks Use Their Senses

27. 60 MinutesSwimming with Sharks • http://www.cbsnews.com/8301-504803_162-57344500-10391709/anderson-cooper-swimming-with-sharks/?tag=mncol;lst;1

28. Shark Mating • Mating behaviour in sharks can be very complex and evidence suggests that there is some degree of mate selection within certain species.  Sexes often segregate, and only come together to mate.  Occasionally congregations form in mating behavior.  For instance, basking sharks have been seen forming mating circles like the one seen in this picture.  The exact purpose of this behavior is not known however it is clear that it related to mating.

29. Shark Mating and Reproduction Mating • http://videos.howstuffworks.com/discovery/36705-ultimate-guide-to-sharks-shark-mating-video.htm • http://www.sharkinformation.org/video/mating-sharks-shanghai-aquarium/JD1_hVJ4ZoM/ Reproduction • http://dsc.discovery.com/videos/shark-week-shark-reproduction.html

30. Shark Birth and Maturation • http://dsc.discovery.com/videos/ultimate-guide-the-sharks-shark-birth-and-maturation.html

31. Female Shark

32. Female Shark

33. Male Shark

34. Male and Female Shark

35. SHARK REPRODUCTION • Oviparous – lay eggs and spawn (ex. White Spotted Bamboo Shark) • Viviparous – give birth to live young who feed from a placenta (ex. Lemon Shark) • Ovoviviparous – eggs are fertilized and develop with a yolk sac inside the mother (ex. Grey Nurse Shark)

36. White Spotted Bamboo Shark

37. Lemon Shark

38. Grey Nurse Shark

39. Grey Nurse Mating • http://news.nationalgeographic.com/news/2006/02/0213_060213_shark_video.html

40. PARTHENOGENESIS IN SHARKS • Give birth to young without mating. An egg develops without fertilization by sperm. One of the mother’s polar bodies fuses with an ovum during meiosis. Was observed in a Bonnethead shark in captivity. http://www.youtube.com/watch?v=jzzg4YEpY28

43. SHARK INTELLIGENCE • Are sharks intelligent? • What would indicate that an organism has intelligence? • http://www.youtube.com/watch?v=zPlTKiSXcG0&feature=list_related&playnext=1&list=SPA15DA8E609E85873 • http://www.youtube.com/watch?v=vG4x7CrCuJU&feature=relmfu

44. SHARK INTELLIGENCE • EVIDENCE • Expressing Curiosity – examining people and objects for no apparent reason (ex. Divers, Square Shapes) (Recognizing certain divers and boats) • Recognizing the front from the back of a person or object (ex. Circling round and spending more time observing the front from the back) • Almost always attack from back • Gently mauling a diver without attacking

45. SOCIAL BEHAVIOR • Sharks were thought to be asocial living their lives alone with little interest in socializing except for mating • Thought to lack the cognitive ability for social behavior • NEW Evidence?

46. EVIDENCE OF SOCIAL BEHAVIOR • GREAT WHITE sharks worked together pulling a Pygmy right Whale out to sea so it could float and be eaten more easily. Some swam away without feeding • Others were shown a square and a seal shape and spent more time examining the square shape

47. EVIDENCE OF SOCIAL BEHAVIOR • Great Whites have been seen spending time together in pairs of same and age peers (2 females show up together each year off San Francisco’s coast

48. SOCIAL BEHAVIOR • Communicate using body language • Arched bodies and gaping mouths (go away) • Individual timed turns between to sharks • Maintaining individual space • Tail slapping • Breaching to attract a mate

49. Shark Self Defense and Shark Attack • How do sharks defend themselves or avoid predation?

50. SELF DEFENSE a. The natural enemies of sharks include other sharks, killer whales and the most dangerous to sharks, by far, are humans b. Gill nets kill sharks and mammals when the intended catch is actually fish. Sharks can drown if they do not have water running over their gills.