Oncorhynchus mykiss Rainbow trout

External Anatomy

HeadTrunkTail

External Anatomy

Pelvic Fins

Anal or VentralFin

Pectoral Fins

Adipose Fin

Caudal or TailFin

Dorsal Fin

Caudal fin: The caudal fin or tail fin is the biggest fin. It provides the “push” for the trout to start moving and also acts as a rudder for steering through the water.

Anal, adipose and dorsal fins: These fins are used for swimming and balance.Pectoral fins: The pectoral fins act as brakes and help the fish turn left and right. Pelvic fins: The pelvic fins help the fish move up and down.

External Anatomy

DarLateral Line

EyeOperculum

Mouth

Scales

Lateral line: Runs from the head of the fish to the tail. It detects vibrations or waves in the water. This helps keep the trout from bumping into things and helps the fish sense danger.

Operculum: This is a hard plate that covers the delicate gills

Eyes: The pupils have a slight triangle shape which helps the trout see above, in front and below its body.Mouth: Trout use their mouths to grab food and feel

things.

Scales: Protect the fish. They grow as the fish grows.

Eye

Trout can see things both near and far away. The large pupils let as much light as possible enter the eye.

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Lens

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The lens in the eye moves around and allows fish to focus on objects.

External Anatomy

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Nostril or Nare

Teeth

The nare is a closed sac. It helps the fish to smell odors.

Teeth are found along the upper and lower jaws. They grasp and hold onto prey.

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MouthGill rakers strain particles out of the water to keep the gills from getting clogged and injured.

Food passes through the esophagus to the stomach.

The tongue has teeth which help to hold onto prey.

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Expose Gill Tissue

Cut off operculum to show the gill.

Gills

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Gill filaments Gill arch

Water is taken in through the mouth and passes over the gills. The gills take in oxygen and release carbon dioxide.

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Carefully cut a flap to expose the internal organs.

Internal Anatomy

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SpleenGall bladderLiverHeart Kidney

Pyloric caecaStomach

Swim bladder

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Kidney

The kidney filters waste from the blood stream and also makes blood. Two canals carry waste from the kidneys to the bladder. From the bladder, the waste passes to the outside through a hole called the vent.

Kidney

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Swim BladderThis is an inflated

swim bladder .

The swim bladder is like a balloon. It allows the trout to float and move up and down in the water. To fill the swim bladder, fish gulp and swallow air. Fish “burp” to get air out of the swim bladder.

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Digestion

Fat IntestineStomach

Path of DigestionMouth

Esophagus

Cardiac stomach

Pyloric stomach

Inte

stin

es

When a trout eats, both food and water enter the mouth. Water is directed to the gills, and food goes to the esophagus which leads to the stomach. Food moves through the stomachs into the intestines and is eliminated out the vent.

Vent

Cardiac Stomach

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Digestion of food starts in the cardiac stomach. Acid secreted by glands activate enzymes that digest protein.

Pyloric StomachThe pyloric caeca act like a small intestine. They release digestive juices needed to break down food and absorb nutrients into the blood stream .

Pyloric caeca

Liver

The liver produces bile which is stored in the gall bladder. Bile breaks down fat.

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Gall Bladder

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The gall bladder is connected to the liver and stores bile made by the liver.

Spleen

The spleen makes and stores blood.

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Heart and GillsCompare the location of the heart to the gills.Why is this important?

Heart

Gills

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Close up of Heart

VentricleAtriumBulbus arteriosus

Heart

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VentricleAtrium

Bulbus arteriosus

The heart consists of two chambers, the atrium that receives the blood and the ventricle that pumps the blood to the body. The blood first passes through the gills where it picks up oxygen, then circulates through the body to the organs where nutrients, gases and wastes are exchanged.

Brain

The brain is the control center of the fish. All sensory information is processed by the brain. Automatic functions (such as breathing) and higher behaviors ("Should I eat that critter ?") happen in the brain.

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Medulla oblongata

Cerebellum

Optic lobes