Fish Anatomy Basics

Fish Anatomy Basics

Gills – The primary function of the gills is the absorbtion of oxygen and the excretion of carbon dioxide and ammonia. Healthy gills are deep red and do not stick together. Unhealthy gills are usually pale and the layers appear to clump. Additional signs of unhealthy gill function are listlessness, flashing and rubbing. Upon examination, damaged gills show excess mucous along with pale color.

Adipose Fin – The adipose fin is a small fin composed of fatty tissue, located b/w the dorsal and caudal fins of some fish, notably characins and catfish as well as Salmonidae. Not all fish have an adipose fin.

Swim Bladder (Air Sac) – Located in the dorsal area of the abdomen, this dumbell- shaped sac is just below the kidney. It allows fish to have buoyancy and balance.

Gonads – These are the reproductive structures, egg sacs in females and testes in males. The egg sack in females may fill a major portion of the abdominal cavity.

Gastrointestinal Tract – This long tubular organ is slightly smaller than the stomach. The stomach is behind the head and above the liver.

Spleen – This organ produces and stores red blood cells and is found embedded in the intestine as a small red mass. Can only be seen after removing intestinal fat.

Pancreas – The pancreas secretes enzymes into the intestine for digestion.

Liver – Liver function is the digestion, filtration and storage of glucose. It appears as a brownish red mass toward the anterior part of the body cavity. The liver also produces enzymes that are stored in the gall bladder that help breakdown food. The liver can only be seen after removing intestinal fat.

Gall Bladder – Digestive enzymes and bile are stored here. It is a small sac found embedded in the liver tissue.

Heart – The heart is a two chambered organ that circulates blood, located adjacent to the gills, just behind the head.

Kidneys – There are two kidneys, one above the air sac and one slightly in front of it. Both are below the vertebrae. Kidneys produce white blood cells and filter wastes.

Brain – This organ is located in the head between but slightly behind the eyes. The brain controls all voluntary and involuntary functions but probably won’t get many rockets off the ground and contains no owner serviceable parts.

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