Chapter 39FishesSection 3

Bony Fishes

Characteristics• Class Osteichthyes • Bone- harder & heavier than

cartridge• Lungs- early bony fishes• Swim bladder- gas-filled sac that

is used to control buoyancy • Scales- protect fish and reduce

friction when swimming

Lobe-finned fishes• Fleshy fins supported by a series of

bones• Lungfish and coelacanth• Lungfish- exchange gas through

lungs and gills (Live in tropical ponds)• Coelacanth- live deep in the ocean

Lungfish

Coelacanth

Ray-finned fishes• Do not have fins with a central

bony axis- fins supported by bony-rays

• Evolved from scales• Familiar fish- trout, goldfish, eels,

bass, guppies, salmon, perch, etc.

Trout

Perch

Goldfish

External Anatomy• Operculum- hard plate that opens at the

rear and covers and protects gills• Fins- swimming and navigation• Caudal fin- tail fin• Two dorsal fins (anterior & posterior)• Ventral anal fin- helps move in a straight line• Pelvic fins- orient body

External Anatomy• Skin- scales• Scales grow with fish• Scales overlap like shingles on

roof

Internal Anatomy• Skeleton- skull, spinal column,

pectoral girdle, pelvic girdle, and ribs• Pectoral girdle- supports pectoral fish• Digestive: Jaws, pharynx,

esophagus, stomach, intestine, liver, gallbladder, pancreas, anus

Internal Anatomy• Circulatory- gills, heart, capillaries

Respiratory and Excretory

• Countercurrent Flow- causes more oxygen to diffuse into the blood

• Urine• Urinary bladder

Swim Bladder• Sac filled with oxygen, carbon

dioxide, and nitrogen• Adjust their buoyancy based on

swim bladder

Nervous System• Brain• Optic tectum- receives and

processes information from the fish’s visual, auditory, and lateral-line systems

Reproduction• External• Lay large numbers of eggs to

ensure survival of species• Spawning- reproduction• Migrate to warm waters to spawn

REVIEW!!!• List three key features that

characterize bony fishes.• Describe the external anatomy of

fish.• Name the importance of swim

bladder.