Fish Dissection

External Anatomy

Characteristics of FishCold blooded Have fins and a backboneMost fish have scales and

breathe with gills22,000 different species of fish

that began evolving 480 million years ago

FinsAppendages used by fish to

maintain its position, move, steer and stop.

Dorsal Fin – top (2)Caudal Fin – tail Pelvic Fin – bottom/belly (2)Pectoral Fin – side (2)Anal Fin - Anus

ScalesComposed of connective tissue

covered with calciumMucus layer covering the body

that helps prevent infectionTwo types:

◦Ctenoid Scales: jagged edges◦Cycloid Scales: Smooth round edges

Some have spines – defensive role

EyesFish can see in colorEyes are rounder in fish than in

mammals Why? Water can distort (change)

images so rounder eyes help the fish focus better in water

Nares/NostrilsPaired nostrils are called naresDetect odors in water and can be

very sensitive

MouthThe shape of the mouth is a clue

to what the fish eatsFish will taste their food before

they eat it to make sure it is edible.

Some fish have teeth

Lateral LineSenses water currents Tiny pores filled with hair-like

sensors that are open to the water

Detects underwater vibrationsDetermines the direction of the

source of the vibrations

Vent (Anus)External opening to digestive,

urinary and reproductive tractsCan be found in front of the anal

fin

Internal Anatomy

MusclesProvide movement and

locomotionUsually the part of the fish that is

eatenFish swim by contracting and

relaxing their muscles

SpinePrimary structural framework

upon which the fish’s body is builtConnects the skull at the front of

the fish and to the tail at the rearMade of vertebrae – hollow and

protect the spinal cord

Spine

Rib Cage

GillsAllows a fish to breathe under waterBreathing apparatus of fish and are highly

vascularized Bright red in colorCollects oxygen from the water so the fish

can breatheProtected by a bony covering called an

operculum – flexible bony plateWater is “inhaled” through the mouth,

passes over the gills and “exhaled” from beneath the operculum

Stomach and IntestinesBreak down and digest food Absorb nutrients from foodCarnivores – short intestinesHerbivores – longer intestines

because fiber in plants takes longer to break down

You can tell a lot about how and what a fish eats by examining the stomach contents.

Stomach

Intestines

KidneyFilters liquid waste materials from

the bloodThese wastes are passed out of

the bodyRegulates water and salt

concentrations within the fish’s body, allowing certain fish to live in freshwater or saltwater

Kidney

Swim BladderA hollow, gas-filled balance organ

that allows a fish to conserve energy by maintaining neutral buoyancy

Allow a fish to float and not sink!Species of fish that do not have a

swim bladder sink to the bottom if they stop swimming

LiverIt assists in digestion by

secreting enzymes that break down fats

Storage area for fats and carbohydrates

Destruction of old blood cells and maintain proper blood chemistry

HeartCirculates blood throughout the

body.Oxygen and digested nutrients

are delivered to the cells of various organs through the blood.

Blood transports waste products from the cells to the kidneys and liver for elimination

Heart

BrainControl center of

the fishProcesses the

sensory information

Decision making skills

Spinal CordConnects the brain to the rest of

the bodyRelays information from the body

to the brainGives instructions from the brain

to the rest of the body

Pyloric CaecaThe organ with finger like

projections located near the junction of the stomach and the intestines.

Secrete enzymes that aid in digestion

VentWaste elimination

Gonads Reproductive OrgansFemale: bright orange mass of

eggs Male: small and white gland

Otoliths“Earstones”Hard, calcium carbonate

structures located directly behind the brain of bony fish.

Aid the fish in balance and hearing

You can count the rings in order to determine the age of the fish.