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Body of the fish

The body

Body of a fish is typically drawn as an elongated spindle, and in fact this is the most commonform, as it makes it easier to swim in open water. These hydrodynamic characteristics permit rapid acceleration and not inconsiderable speeds (some times up to 20 km per hour) in a medium (water) hat offer a certain degree ofresistance. However, there are other forms that are also all connected with the life style of the fish in question: bottom-dwellers have a flat stomach, while those that live in water obstructed by plants and branches have compact, thin bodies that enable them to squeeze through the obstacles. This is equally thecase with the countless fish in the coral reefs, which thread their way through the blocks of coral. Finally, there are certain fish that are unclass ifiable,so varied and strange are the forms they flaunt, although they always correspond to a particular life style.

Body of a fish

The fins

Fish have several types of fins, each one playing a precise role. Their forms and names are often used to classify them into different families. Of the unpaired fins(i.e. consisting of a single fin), the most note worthy are the dorsal and the anal fins. These serve to stabilize the fish when it is not going very fast or is coming to a halt, and they are tucked in when the fish swims more quickly. The caudal fin (incorrectly referred to as the tail) supplies propulsion, in conjunction with the rear part of the body.In some species, particularly the Characins and the catfish, there is a smallextra fin between the dorsal and the caudal fins, known as the adipose fin.

The head

What ever its form - conical,elongated, or stocky - the head houses some important organs:- first of all,there are the eyes, which have no eyelids and are highly mobile. This mobility, coupled with their position on the side of the head, allows a fish to command a broad field of vision - around 270°. In contrast, the clarity of its vision is unexceptional:beyond a certain distance, it distinguishes masses and forms rather than details. Fish are very sensitive to variations in light - detecting lowintensities of light, such as that of the moon - and they can recognize colors.- next comes the mouth, with a size and shape related to its feeding habits. Carnivorous fish generally have a large mouth that can open wide and is endowed with an array of pointed teeth, which are sometimes curved to wards the back to keep hold of their prey. Omnivorous and herbivorous fish have a smaller mouth,with flat teeth ideally suited to grinding food.

fish vision
Fish have a particularly wide field of vision

The position of the mouth can similarly reveal eating habits:

fish mouth

• a mouthin the upper position indicates a top-feeder;

• a mouthin the terminal position is the sign of a fish that hunts underwater;

• a mouthin the lower position indicates a bottom-feeder.

Breathing

Water is aspirated through the fish's mouth, passes through the branchiate and is expelleddue to the movements of the operculum, which covers them. There is always some water washing the branchiate of the fish. Oxygen requirements are not directly proportional to the size of the fish, with the smallest species being the greatest consumers of oxygen: ten fish weighing 1 g each consume more oxygen per gram of body weight than onefish of 10 g.

The barbels

fish barbels

Fish that live on the bed or in dark environments (colored or turbid water) have barbelsaround the mouth (Corfdoras, Botia, for example). These appendages havea tact