Flatfish is a strange fish with two eyes on one side. It is considered that two fish should walk side by side, hence its name. It is a large class of marine fish, including fish of Silurus, Solenidae and Solenidae. Common in the family Paralichthyidae are PARALICHTHYS olivaceus, PARALICHTHYS olivaceus and PARALICHTHYS olivaceus. The common flounder families are high-eyed flounder, stone flounder, wood leaf flounder and oil flounder. Cynoglossus is a common species in the family Cynoglossus. There are 3 suborders, 9 families, about 1 18 genera and 538 species. 3 suborders, 8 families, 50 genera 134 species in China. They are all bottom-layer marine fish, and their distribution is closely related to the environment, such as ocean current, water and water temperature. For example, along the western side of the equatorial oceans, the warm current is wide and there are many kinds; There is a strong cold current along the coast of the Yellow Sea and Bohai Sea, and there are many cold and warm types. The western Pacific and the South China Sea were not strongly affected by the ice age, and there were many kinds. There are a few species in China, such as Silurus meridionalis, Cynoglossus altissima, Cynoglossus maculata and so on, which can live in fresh water areas of rivers.

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Flatfish, also known as flatfish, flatfish and fish, inhabit the sandy bottom of shallow sea and prey on small fish and shrimp. They are especially suitable for benthic life on the seabed. Because their bodies are flat. Both eyes are on the upward side of the body, and the color of this side is well matched with the surrounding environment; Their downward side is white. The flounder has extremely fine scales on its body surface. The flounder has only one dorsal fin, which extends almost from the head to the caudal fin. They mainly live in temperate waters and are important economic fish in temperate waters. How did the flounder's eyes get together? It turns out that the flounder larvae just hatched from the egg membrane are completely unlike their parents and look very similar to ordinary fish. Eyes are on both sides of the head. One on each side, placed symmetrically. They live in the upper layer of water and often swim near their sleep. After about 20 days, the morphology of flounder larvae began to change. When the larvae of flounder reached 1 cm, something strange happened. The eye on the flounder side began to move. It gradually moves to the opposite side through the upper edge of the head and stops moving until it is close to the other eye. Different kinds of flounder eyes have different methods and routes to move. The skull of a flounder is made of cartilage. When the flounder's eyes start to move, the cartilage between the flounder's eyes is first absorbed by the body. In this way, there is no obstacle to the movement of eyes. The movement of flounder's eyes changes the internal structure and organs of flounder. Flounder has not adapted to floating life, so it has to lie on the bottom of the sea. Flounder is a valuable seafood. It is called PARALICHTHYS olivaceus in fishery. The body of PARALICHTHYS olivaceus is generally 25 cm to 50 cm long, and the largest PARALICHTHYS olivaceus is 70 cm. Paralichthys olivaceus will make short-distance group migration according to the change of seasons. Paralichthys olivaceus is widely distributed along the coast of China. Fishermen in the Yellow Sea and Bohai Sea use bottom trawls to catch flounder. Fresh PARALICHTHYS olivaceus can be eaten or canned. The liver of PARALICHTHYS olivaceus can also extract cod liver oil.

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Ichthyologists tell us that this strange shape of flounder is not innate. The newly hatched flounder's eyes are also born on both sides. When it grows to about 3 cm long, its eyes begin to "move". One eye moves to the top of its head, and gradually the upper edge of its head moves to the other side until it approaches the other eye. The life habit of flounder is very interesting. When swimming in the water, its back is not up like other fish, but its side with eyes is up and it swims sideways. It often lies flat on the bottom of the sea, covered with a layer of sand, with only two eyes exposed to wait for prey and avoid predation. In this way, the advantage of two eyes on one side is displayed, which is of course the result of animal evolution and natural selection.

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In fact, the ancients had a wrong understanding of flounder. "Er Ya Shi Di" said: "There is a contrast between the eyes and the eyes in the East, and it is no better than it, so its name is the sole. "Wu Du Fu" also said: "The double is more than the eye, and the piece is Wang Yu. (Note: "The flounder comes from the East China Sea. Wang Yuyu, his body is half. As the saying goes, the silver carp of the king of Yue is not exhausted, so it is half abandoned in the water as a fish, so there is no one side, so it is called Wang Yuye. ) The reason why the ancients called it a flounder was because it was "like a bovine spleen, with thin scales and purple black. At a glance, two pieces fit together, so it was called a flounder. As I have said before, the flounder is indeed a strange fish with eyes on one side and no eyes on the other, but it is not only one eye, but two eyes are close to one side. It is even more wrong to say that it is "two pieces that fit together". How can two fish be closed together? Different kinds of flounder have different eye positions. The eyes of the flounder family are on the left, but the eyes of the sole family and the sole family are on the right.

In ancient China, flounder was a strange fish symbolizing loyal love. The ancients left many beautiful sentences praising flounder, such as "The Phoenix is an amphibious fish", "Why don't you quit your job if you get a better one? You would rather be a mandarin duck than a fairy", etc. Li Yu, a famous dramatist in Qing Dynasty, once wrote a script describing the love story of a talented person and a beautiful woman, and its name was "Flounder".