Fish Notes

1
Fish Notes

• Sharks

2

• Class Chondrichthyes skeleton made of
  cartilage tooth-like scales covering their skin.

• Characteristics
• Placoid scales have a pointed tip which faces
  backwards. (denticles)
• Heterocercal tail upper lobe is longer than the
  lower lobe.
• 3. Gill slits not covered by an operculum (5-7
  gill slits)

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Characteristics, contd

• 4. Cant 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

4
Senses

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

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
• 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!