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A fish does not have eyelids as do human beings. It looks at the
world through a transparent curtain covering its eyes. This curtain
resembles a diver's eyeglass. Since they usually need to see objects very
close to them, fish's eyes have been created to meet this need. The
spherical and hard structure of their eyes are adjusted to see objects
close to them. When they want to look at an object at a distance, the
lens system is drawn backward by means of a specific muscle
mechanism in the eye.
Beside its five basic senses of sight, smell, hearing, touching and
taste, the fish also perceives the outside world through its "lateral"
lines. Sensitive nerves that lie along these lines perceive the size and
direction of objects the fish passes by. In this way blind cave fish can
move very easily in the dark. This system is a kind of underwater radar
or "sonar" system.
Furthermore, many fish species have a long and slender balloon-like
air-filled sac in the abdominal cavity. They maintain their balance in
the water with the help of this sac.
Fish of various kinds created by the will of Allah amaze people with
their beautiful colours and movements. You can hardly find such vivid
colours as those seen in many fish in any other animal.
