Fish ears have two functions, one is used to listen to sound, and the other is used to maintain balance. Although a fish does not have ears from the outside, it has special sound receivers that can transmit sound waves to the inner ear. The tubes in its inner ear are filled with fluid and have cilia that transmit sound impulses to the brain.
1, spindle shape: spindle shape is the most common shape of fish, also known as the basic type, the overall shape is like a spindle, some slightly flat, three body axis, the head and tail axis is the longest, followed by the back and abdomen axis, left and right axis is the shortest, so that the body is streamlined, especially suitable for swimming in the water, resistance is very small. This kind of fish mostly inhabits the middle and upper water.
2. Lateral flat type: The left and right axes of the lateral flat type fish are particularly short, and the ratio of the cephalocaudal axis to the dorsoventral axis is almost the same, so it looks very large from the side, but it is very thin from the top to the bottom. This type of fish is not as strong as the spindle type in swimming ability, so it cannot migrate for a long distance. Common fish are pomfret, swallow fish, bream, butterfly fish and so on.
3. Stick type: The head and tail axis of the stick type fish is particularly long. The whole fish looks like a snake. The left and right axes are basically the same as the dorsal and ventral axes. Swimming ability is relatively strong, usually in the bottom of the soil in the cave. The common ones are eel, eel and conger eel.
4, flat type: flat type of fish left and right axis is very long, dorsoventral axis is very short, looks very thin, this kind of fish action is relatively slow, generally live in the bottom of the water. There are common rays, rays, anglerfish, and so on, there are some body changes, such as sunfish, flounder.
