today’s fishes section 33.2. jawless fish - agnathans lampreys and hagfish scaleless eel-like...
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TODAY’S FISHESSection 33.2
JAWLESS FISH - AGNATHANS
• Lampreys and hagfish• Scaleless• Eel-like bodies• Multiple gill slits• Unpaired fins• Skeletons of cartilage• Hagfish – ‘vultures of the sea’ scavengers• Lamprey – parasites on other living fish
HAGFISH
LAMPREYS
CARTILAGINOUS FISHES
• Sharks, skates and rays• Skeletons made of cartilage
strengthened with calcium carbonate – lightweight and strong• Streamlined body• Placoid scales – give skin a rough
texture• Teeth are modified scales and are
replaced as needed throughout lifetime
SHARK
SKATEROUNDISH OR TRIANGULAR SHAPE
RAYKITE-SHAPED WITH 1 OR MORE VENOMOUS BARBS IN THE TAIL
BONY FISHES
• Largest group of fish• Endoskeleton made of bone• Lateral line system – acts as a sensory organ to
detect movement in the water (theirs and other objects)
• Operculum – hard gill cover which allows fish to move water over the gill while remaining still in the water
• helps fish conserve energy• Swim bladder – allows fish to maintain water
depth • gas in fish rises; gas out fish sinks• Two groups: ray-finned fish & lobe-finned fish
RAY-FINNED FISH
•Most fish are in this group•Teleosts – the most advanced •Highly mobile fins•Very thin scales•Completely symmetrical tails•95% of all fish species
YELLOW PERCH – A RAY-FINNED FISH
LOBE-FINNED FISH
•Only 7 species – 1 coelacanth + 6 lung fish• Each fin has a long, fleshy, muscular lobe supported by a central core of bones•May be a direct ancestor of amphibians, but probably not
COELACANTH
LUNG FISH