The self-protection habits of flounder

The shape of the flounder is different from other fish in that its eyes are on one side. I usually live my life lying on my side. The upward side has eyes and colors, the downward side has no eyes and no color, and the color of the upward side can change with the color of the environment. The special shape and color of the flounder is a special metamorphosis formed during its long evolutionary process in order to protect itself and resist enemies.

The metamorphosis of flatfish begins in the larval stage. The newly hatched larvae and other fish have symmetrical bodies with left and right sides, and their eyes are also symmetrical, that is, one eye on each side. They swim in the upper layer of the water in the same way as other fish. When the larvae grow to more than 15 mm, one eye gradually moves to the top of the head, crosses the upper edge of the head, and moves downward from the other side until it is close to the other eye. At the same time, when the eye on one side moves, the dorsal fin also extends forward. When the eye on one side moves over the top of the head, the dorsal fin also extends to the back edge of the head. With both eyes on one side of the head, the originally symmetrical skull also changed to adapt to the new lifestyle. Changes in the position of the eyes also prompt changes in its lifestyle. When the two eyes move to the same side, the fish will sink to the bottom of the water body, live on its side at the bottom of the water, or swim in the water close to the bottom. At this time, fish with eyes The side of the eye must be upward, and the side without eyes must be downward. Pigments are produced on the side with the eyes facing upward, and the original curved appearance is maintained. There is very little pigment production on the side without eyes, mostly white, and a few individuals are scattered with brown or black markings. At the same time, the shape of the downward side is cut flat, just like the half of a fish cut open from the midline.

In addition to its special metamorphosis ability, another way of self-protection is to change color. It can quickly change the color of its body to resemble the environment in a short period of time. This ability to unify body color changes with the environment is Incomparable to other fish. Usually, the discoloration range of flounder is limited to the colors of the ordinary environment. For black, white, brown, gray, yellow and other colors, the color change can be completed in an instant. It is more difficult to change to red, and it takes longer for blue and green. Sometimes it needs to be extended to about half an hour.

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