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Odyssey Expeditions Sharks. Sharks. Class Chrondrichthyes -cartilaginous skeleton All are carnivorous Poikilotherms Rough, thick skin, Placoid scales Elongated body Countershading Have no swim bladder, must swim to keep from sinking Specialized sensory system. Shark Diversity.
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Sharks • Class Chrondrichthyes -cartilaginous skeleton • All are carnivorous • Poikilotherms • Rough, thick skin, Placoid scales • Elongated body • Countershading • Have no swim bladder, must swim to keep from sinking • Specialized sensory system
Shark Diversity • Of 300 species known… • Only 10 attack man • Found in all ocean environments • Efficient predators • Range in size from 4” to 30’ • Long fossil record, over 450 million years
Shark Feeding Mechanisms • Jaws and teeth • All are carnivorous, feeding on plankton to meat • Pelagic and some benthic • Lateral line system • Aids in prey location
Shark Vision • Rods and cones • Moving lens for close-up viewing • Reflective layer behind retina--dim objects (tatum lucidum) • Protective membrane covering eye
Shark Reproduction • Internal fertilization • Two ways to bear young: • Oviporous • Spotted dogfish • Whale shark • Ovoviviporous • Mako, thresher, sand-tiger: babies cannibalize • Hammerhead: up to forty to fifty pups
Electroreception in Sharks Lateral line-extensive in most sharks Cephalic canal: head region Ampulae ofLorenzini: pores in head that detect temperature and electric fields Shark Bouyancy Lack swim bladder Heterocercal tail Oily livers Cartilage Pectoral fins Osmoregulation Urea in bloodstream, with special adaptation to prevent toxicity More Shark Adaptations
Shark attacks Typically 50 per year in US, 100 worldwide are reported 2001, The Summer of the Sharks? What to do: Watch out and get out Nets, aerial spotters Bang sticks Blow to head, gouge eyes (?) Shark stocks Low reproductive rate Easily overfished Highly restricted fisheries Shark Attacks?