Fish Facts

  • Fishes are cold-blooded and they can't control their body temperature.
  • Fish can feel pain. They have a good sense of taste, sight and touch. Many fish taste without opening their mouth.
  • Whale shark is the largest fish and they can grow to 50 feet long.
  • Fish like Trigger fish can swim backwards.
  • If gold fish is kept in a dark room it will lose its color.

Internal Anatomy:

The internal organs of the fish perform the basic function of the body such as respiration, digestion, and sensory function. The brain, stomach, liver, and kidneys are same as in man for the fish and perform the same function. Some organs are different; man has lungs to breathe whereas fish has gills for the same purpose. The name and function of the internal organs are listed below with their functions.


The fish body is built on this main structural framework. This unit is connected to the skull at the front and to the tail at the back. Numerous vertebrae that are hollow make up the spine. These vertebrae house and protect the subtle spinal cord.

Lateral Line

Lateral line is one of the fish sensory organs which help the fish to detect vibration in the water and to format their direction of source.

Swim Bladder or Air Bladder

Swim bladder is hollow and gas filled organ. It allows the fish to conserve energy by enabling neutral resilience in water. Fishes that is deep in the water needs to release air from their swim ladder when they come up this is due to the difference in atmospheric pressure that circulate in the water surface. Fishes that do not possess an air bladder sink to the bottom of the water if they stop swimming.


Gills help the fish to breathe under the water. Gills are the weak organ and it should not be touched by the hand when the fish is alive.

Pyloric Caeca

This organ is present at the junction of the stomach and intestine. It has a finger like projection and its function is to secrete enzymes that help in digestion. It also helps to absorb the digested food.


This organ is used to eliminate the waste from the fish body.


Gonads are the reproductive organs for the fish. In female fishes the bright organ that contains collection of eggs is clearly identifiable during the spawning period. The male reproductive organ is much smaller and less white in color. It produces milt for fertilizing the eggs.


This organ is also used for locomotion. This part is usually eaten by man as it contains certain vitamin deposits. Muscles compose the bone of the fish.


See also -> External Anatomy

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