Fish

• Live in salt, brackish and freshwater• Cold Blooded – body temp

matches surroundings

Advantages

• Fins - Paired fins increased stability and maneuverability in water

Jaws

• Jaws allowed fish to seize and manipulate prey

Characteristics

• Internal Skeleton• Most breathe with gills• Lateral line• Swim bladder• 2 chambered heart• Mucus covered scales

Respiration

• Fish use gills for gas exchange• Countercurrent flow - water

flows across the gill filaments in a direction opposite to blood flow.

Lateral Line

• A system of canals in the skin that allow fish to sense vibration in the water• also have fluid-filled inner ears for

hearing

• Some fish (cartilaginous) also have sensory organs known as “Ampullae of Lorenzini” that can detect weak electrical signals• Can locate prey by detecting their

muscle contractions

Swim Bladder

• Used to control their position in the water (can stay at one depth).

Spiny Pufferfish swim bladder

Circulatory System

• 2 chambered heart – pumps blood to the gills to pick up oxygen

Scales

• Head to tail (reduce drag)• Grow rings

every year• Tell fish’s age

Scales

• Secrete mucus to reduce friction as they swim, and to reduce the risk of infections.

• Protected by the “operculum”

Operculum

Countershading - a type of camouflage in which the dorsal (top) side is darker than

the ventral (bottom) side.

Chemoreception

• The ability to detect chemicals in the environment–Include smell & taste–Most fish have a well developed

sense of smell

3 Classes of Fish

• Agnatha • Chondrichthyes • Osteichthyes

Agnatha (no jaw)

• Lamprey and Hagfish• Absence of jaws. –Circular toothed mouth to bore

into the side of a fish and suck the blood.

Lamprey are parasites

Hagfish

Hagfish are scavengers

Agnatha

• Skeleton made of cartilage.• Eel-like body • Soft skin/no scales• Oviparous (egg laying)

–External fertilization

Chondrichthyes (cartilaginous)

• Sharks, Rays & Skates –about 1,000 living species.

Rays and Skates

• Flattened kite or triangular shaped bodies with long whiplike tails

Giant Manta Ray

Skate

Sharks

• Streamlined body and muscular tail

Teeth

• Several rows of triangular teeth

• Replaced as they are lost

Respiration

Pump water by: Swimming rapidly Or by expanding and contracting

their mouth

Body covered with small, triangular placoid scales.

Fins

• Large caudal fin• Dorsal section larger than ventral

one. • Paired fins (pectoral and pelvic), are

nonflexible.

• Sharks lack a swim bladder. –Store large amount of lipids in the liver–Can be 25% of shark’s mass

Acute sense of smellSharks can detect 1 drop ofblood in a square mile of water

Ectothermic – cold blooded

Reproduction

• Internal fertilization.–Modified pelvic fins called claspers

deposit sperm• Ovoviviparous - give birth to live

young, the eggs develop without any nutrition from the parent

Osteichthyes – bony fish

• Largest class of vertebrates with over 29,000 species (95% of all fish)

• Bony skeleton• Paired fins, or lobed fins • Some have sensory whiskers

(barbels)–Catfish, bullhead

Lobe-finned fish

• Muscular fins supported by bones.• Their "lung" is a modified swim

bladder• Able to survive dry spells • Can drown if kept underwater and

not allowed to breathe air!

LUNGFISH

COELACANTH

Ray-finned fish

• Most bony fish are ray-finned fish, meaning that they have thin, flexible skeletal rays. –Make up half of all living

vertebrates

External Fertilization (Spawning)

–Lay numerous eggs (high mortality)–Some migrate great distances (salmon)–Always return to place where they

were hatched (can travel thousands of miles, jump dams etc.)