In this article we will discuss about the Structure of a Typical Fish.
Fishes are cold blooded animals, typically with backbone, gills and fins. The body of a typical fish comprises the head, trunk and tail. The head bears two eyes, with well developed nictitating membrane, two internal ears, two nostrils which are closed internally (except in lung fishes) and mouth. Behind the head on each side, there are either gill slits or gills meant for respiration.
The gills are usually covered with a lid like structure, the operculum. Since the neck is absent the head is continued into the trunk. Paired or unpaired expansions of the skin are called fins.
Of the paired fins, there are generally anterior pectoral and posterior pelvic fins, which correspond to our arms and legs respectively. The unpaired fins of the trunk region are generally dorsal fin (may be two, rarely three) and ventral or anal fin, which is present ventrally (near the anus or cloacal aperture).
The expanded part of the fin is supported by thin skeletal rods, known as the fin rays. The trunk bears anal or cloaca aperture. The part of the body behind the anus is designated as tail, which is of different shapes in different species. It always has caudal fin (tail fin) which is also supported by fin rays More or less, all the fins are helpful in swimming.
A peculiar system of sense organs, the lateral line system, is present in the fishes. One lateral line on each side can be seen easily. The body of a fish may or may not be covered with scales. The sexes are separate. They are usually oviparous, but ovoviviparous or viviparous forms are also found.