fish live in salt, brackish and freshwater cold blooded – body temp matches surroundings
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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
Scales
• Secrete mucus to reduce friction as they swim, and to reduce the risk of infections.
• Protected by the “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
Agnatha (no jaw)
• Lamprey and Hagfish• Absence of jaws. –Circular toothed mouth to bore
into the side of a fish and suck the blood.
Agnatha
• Skeleton made of cartilage.• Eel-like body • Soft skin/no scales• Oviparous (egg laying)
–External fertilization
Fins
• Large caudal fin• Dorsal section larger than ventral
one. • Paired fins (pectoral and pelvic), are
nonflexible.
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
• 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!
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