Marine Fish

Intro to Fish

• Fish– The most common and diverse vertebrates in the

ocean– Evolved around 500 million years ago– 20,000 different species worldwide (freshwater &

marine)

Jawless Fish

• Superclass: Agnatha• Lack jaws and paired fins• Cyclostomic toothed mouth used to bore into

and suck blood from their victims• Most have a skeleton made of cartilage

Examples of Jawless FishSea Lamprey• Eel-like in appearance• Two dorsal fins • Can live in fresh or salt water • Parasitic as adult

Hagfish• Have 3 hearts• Can form an exterior cocoon from

slime that they produce• Can go up to 7 months without

eating

Jawless Fish Feeding

Bony Fish

• 95% of fish• Have a skeleton made of

bones• Protective covering of scales

that are easily removed• Skin secretes mucus to act

as a barrier for infection and to reduce friction

Breathing in Bony Fish• Fish breathe by letting water in through the mouth,

passing over the blood-filled gills

Locomotion in Fish• Fish that can swim are known as

nekton• Streamlined shape helps fish

swim faster• Temperature affects speed– Cold water = slower speed

Buoyancy in Fish

• Swim bladder: internal gas-filled organ that helps fish stay afloat when they are not swimming

Food-Gathering• Mouth shape & structure

depends on feeding method and prey– Straining plankton out of

water– Bottom dwellers have

vacuum like mouths to suck in food

– Beaklike mouths for nibbling on chunks of coral

– Strong flat teeth for crushing shells of invertebrates

– Predatory fish with large sharp teeth

Reproduction in Bony Fish• External fertilization and development• Spawning: the release of gametes during external

fertilization

Senses

• Lateral line senses vibrations from water • Detect low-frequency vibrations and

directional water flow• Function in distance perception• Fluid-filled canals open to water through tiny

pores