Today’s Fishes Section 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

Skate roundish or triangular shape

Ray kite-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