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 smell Sharks can detect 1 drop of blood 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.)