Generally speaking, the eyes of animals are distributed at the left and right ends, which are symmetrical to each other. But there are also animals that are different. This animal is the flounder. What is special about flounder is that its eyes are distributed on the same side of its head. Is this unique position because of innate genes, or is it "long-disabled" when it grows up the day after tomorrow?

In fact, flounder is no different from other fish when it is just born. Its eyes also grow evenly on both sides of the head, one on each side and symmetrically distributed. But after a while, about twenty days, something amazing happened. The shape of the flounder began to change. When its body grew to about one centimeter, one side of the flounder's eyes began to move sideways. The flounder's eye moves through the upper edge of its head, then slowly moves to the opposite side until it is close to the other eye.

There are many kinds of flounder. Different kinds of flounder have different methods and routes of eye movement and different looks. For example, the eyes of the flounder and the tongue sole are on the left, while the eyes of the sole are on the right. So, how do the flounder's eyes move? This requires the help of the unique body structure of flounder. The skull of flounder is different from other animals. It is not hard bone, but cartilage. When the flounder's eyes begin to move, the cartilage between the flounder's eyes will be absorbed by the body first. With the absorption of cartilage, the movement of eyes loses its obstacles, and it is more comfortable to move.

As the eyes move, the body structure of flounder becomes different. Their dorsal fin and gluteal fin also grow forward to the head, and their bodies are twisted sideways. After about a hundred days, the flounder grows into their parents. In addition to the different body structure, the living environment of flounder is also different. When the flounder was born, it moved near the water surface, but when its eyes moved to the same side, the flounder gave up floating on the sea surface and moved to the bottom of the sea.

The flounder usually swims sideways, and it often lies flat on the bottom of the sea, covered with sand. In order to find the enemy faster, it is undoubtedly the best choice to have two eyes together. Generally speaking, the unique position distribution of flounder eyes is not innate, but changes with the environment and the needs of survival.