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Odyssey ExpeditionsOdyssey Expeditions

SharksSharks

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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

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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

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Hammerhead

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White-tipped Reef Shark

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Nasty Looking Sharks

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Bottom Dwellers

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Whale Shark

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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

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Eating Eating MachinesMachines

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Shark Vision

• Rods and cones• Moving lens for

close-up viewing• Reflective layer

behind retina--dim objects (tatum lucidum)

• Protective membrane covering eye

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Shark ReproductionShark 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

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More Shark Adaptations• 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

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Shark Attacks?• 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