1. Fish Notes Sharks

2. Class: Chondrichthyes – skeleton made of cartilage & tooth-like scales covering their skin. Class: Chondrichthyes – skeleton made of cartilage & tooth-like scales covering their skin.Characteristics 1.Placoid scales – have a pointed tip which faces backwards. (denticles) 2.Heterocercal tail – upper lobe is longer than the lower lobe. 3. Gill slits not covered by an operculum (5-7 gill slits)

3. Characteristics, cont’d 4. Can’t swim backwards 5. Sharks have no swim bladder so they sink – to compensate they have a very oily liver – it can be up to 25% of their body mass. 6.Sharks vary greatly in size 7.Smallest –dwarf shark 6-8 inches Largest – whale shark 60 feet Largest – whale shark 60 feet

4. Teeth –some species can go through 20,000 teeth in a lifetime. –Broken teeth are replaced from those behind – like a conveyor belt. Senses

5. Senses Ampullae of Lorenzini – hundreds of tiny holes in the face of a shark which helps them pick up electrical impulses given off by living prey items. Hearing – best sense – can hear prey in the water from 3,000 feet away. Lateral line – detects differences in water pressure to help fish detect obstacles in their path.

6. Senses Smell – well developed. They can detect 1 part blood per 100 million parts of water. 2/3rds of brain devoted to sense of smell Eyesight - certain sharks have evolved a special "nictitating membrane" on the lower lid of the eye that protects the eye from thrashing fish during feeding frenzies. They can see well in low light.

7. Shark Attack!! Shark Attack – 25 species have attacked man Shark Attack – 25 species have attacked man –3 most dangerous are Great White Shark, Tiger Shark and the Bull Shark –Chance of being attacked is less than being hit by lightning. –Most likely to attack in shallow water (less than 4 feet) –If attacked hit on nose or stick fingers in gills or eyes!