Sharks

SharksRead pages 155-159 & 174-177

See also: http://www.flmnh.ufl.edu/fish/education/questions/basics.html

Types of Fishes – Where Do Sharks Fit In?

• Three types: Jawless, Cartilaginous, & Bony

• Sharks fall into the Cartilaginous category– Primitive fishes– No true bones, only

cartilage– Related to skates and rays– Most are harmless– See the model in C114

Shark Diversity• The smallest shark is a

deepwater dogfish (adults are about 8

inches long)

• The largest shark is the whale shark

(a planktivore)

• The fastest shark is the shortfin mako

(swims up to 20 mph)(Note: Average person

swims about 3 mph)

http://dsc.discovery.com/videos/ultimate-guide-to-sharks-the-many-species-of-sharks.html

Shark Bodies• Notice that sharks are fish and obtain

oxygen from the water through their gills-usually 5 – 7 gills

Shark Bodies Cont.

Lost teeth are replaced in a

“conveyor belt” system, with back teeth

moving forward to

replace lost ones

Shark Bodies Cont.• Placoid Scales – sharp-edged scales can injure

prey; gives shark skin a sandpaper-like feel

• Liver – very fatty; helps shark maintain buoyancy

• Tail-upper lobe is usually longer for better power & thrust

• Usually two dorsal fins, paired pectoral fins

Shark Reproduction• Fertilization

is internal

• Males use claspers to insert sperm into female’s cloaca

Shark Reproduction Cont.• Some sharks are

Oviparous (lay an egg-mermaids’ purse)

• Some sharks are Ovoviviparous (have an egg that develops inside female-sometimes eating siblings!)

• Rarely, sharks can be Viviparous (Live-bearers-like mammals)

http://dsc.discovery.com/videos/ultimate-guide-to-sharks-how-are-sharks-born-take-a-look.html

Shark CamouflageCountershading –

darker on dorsal surface to blend with the deeper water or

the sea bottom & lighter on ventral

surface to blend with lighter colored surface waters,

making it difficult for both predators & prey

to see a shark

Shark Trouble• Most sharks need to force water over gills to

breathe, and can “drown” when trapped in nets

• Skin, oil, and fins are overharvested to the point of near extinction for some species

• PSA aimed at stopping these practices: http://

www.youtube.com/watch?v=fkxoRPv4ugE&playnext=1&list=PLB4E6B7A755C66293

Additional Shark Links• More on the importance of sharks in

healthy oceans: http://www.youtube.com/watch?v=xVKrwsXvC0A&feature=autoplay&list=PLB4E6B7A755C66293&index=5&playnext=2

• Clearinghouse of all known Shark links: http://www.postmodern.com/~fi/sharklinks/links.htm

• More general shark information: http://www.youtube.com/watch?v=xVKrwsXvC0A&feature=autoplay&list=PLB4E6B7A755C66293&index=5&playnext=2