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Class Chondrichthyes

Class Chondrichthyes. JAWS. Teeth are modified scales Bottom jaw is like a fork for grabbing and holding prey Top jaw is like a knife with serrated edges to cut through prey Bite strength: 132 lbs. between jaws = 22 tons/in 2 at tips of teeth!. BODY. Fusiform body Usually countershaded.

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Class Chondrichthyes

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  1. Class Chondrichthyes

  2. JAWS • Teeth are modified scales • Bottom jaw is like a fork for grabbing and holding prey • Top jaw is like a knife with serrated edges to cut through prey • Bite strength: 132 lbs. between jaws = 22 tons/in2 at tips of teeth!

  3. BODY • Fusiform body • Usually countershaded

  4. FINS • Dorsal: stabilization • Pectorals: steering • Pelvic: stabilization • Anal: stabilization • Caudal: steering, power, propulsion

  5. CAUDAL FINS • Homocercal: top and bottom lobes are equal in length (GWS). • Heterocercal: top lobe is longer than bottom lobe.

  6. GILLS • Most sharks have 5-7 pairs • 6 and 7-gill sharks probably represent closer link to ancient sharks

  7. SCALES • Placoid scales • Dermal denticles (skin teeth)

  8. EXTRAS • Spiracles: respiratory structures present in certain chondrichthyes located just behind the eyes. Water intake valves. • Spiral Valve:In stomach; increases surface area for absorption. • Squaline Oil:In liver; increases buoyancy.

  9. MORE EXTRAS • Opportunistic feeder:Feeds when the opportunity arises. • Obligate swimmer:Must swim in order to respire. • Tonic immobility: Process by which shark becomes “paralyzed” by turning it over on it’s back (It appears to go to sleep). This is a temporary state!

  10. SENSES(in the order that they detect prey) 1. Hearing: sound travels faster in water, attracted to low frequency sounds emitted by old, injured and /or dying fish 2. Smell: Blood trail (chum) stimulates sense of smell 3. Lateral line: feel vibrations from wounded prey

  11. SENSES 4. Vision: can spot prey from 30 yards -nictitating membrane protects eyes. 5. Electroreception: (from Ampullae of Lorenzini) Jelly-filled sacs that detect electrical fields given off by all living things, open wounds, etc. --Can detect up to one millionth of a volt 6. Taste: upon contact with prey

  12. REPRODUCTION Oviparous: Young hatch from egg laid outside the mother. Cat shark, Horn shark, Swell shark Viviparous: live born sharks. Each fertilized egg develops inside a separate compartment in the mother’s oviduct. Pup is feed via a placenta. Lemon, Blue, Bull, Hammerhead

  13. REPRODUCTION Ovoviviparous: embryo develops in a large yolky egg kept inside the female’s oviduct. Embryos hatch while still inside the mother then develop more before being born. --Sand Tiger, Thresher display interuterine cannibalism: where first pup to hatch in each uterus will eat its siblings. Claspers: Two fingerlike projections at the base of the pelvic fins in MALE sharks, (skates and rays).

  14. 4 Most Dangerous Sharks Oceanic Whitetip Great White Bull Tiger

  15. SHARK ATTACKS • Most shark attacks occur on sunny days in near shore waters 20C or warmer. • Great White sharks prefer colder waters. • Most common body parts attacked are the calves and knees. • Typically sharks will show an Agnostic Displaybefore they attack: back is arched, pectoral fins are pointed down, and shark swims erratically.

  16. WILL YOU BE ATTACKED? • You have a better chance of being killed by a pig, bee, snake, elephant, plane or car crash. • You have a better chance of winning the lottery. • You have a better chance of getting struck by lightning twice in the same spot.

  17. THE HARD TRUTH • Fisherman kill between 30-100 million sharks / year. • Sharks kill between 10-15 humans/year. • That means that for every single human killed, there are 10 million sharks killed!

  18. RAYS • Identified by the presence of a barbed stinger on their tail. • Swimmers can do the “Stingray Shuffle” to avoid getting stung. • If a person gets stung, immerse the body part in hot water to denature (break down) the protein-based venom.

  19. Ray MigrationGulf of Mexico

  20. SKATES • Skates have a pointed “nose”, spots and thorns or spikes on their bodies, but no stinger. • Egg cases are called “Mermaid’s Purses” and are commonly found washed up on beaches.

  21. CHIMAERAS • Often called Ratfish or Rabbitfish. • Have a venomous spine at the front of the first dorsal fin. • Males have a 5thclasper on their head.

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