The highest fish on earth

On the Qinghai-Tibet Plateau in my country, there are two types of fish unique to the plateau - Schizothorax and Loach fish. Due to the influence of climate and environment, they all have unique external and internal structures to adapt to their living environment.

Schizothorax Schizothorax is a unique economic fish of the Qinghai-Tibet Plateau. The body is generally longer and has strong swimming ability to overcome the impact of running water. The black peritoneal membrane in their abdominal cavity can block strong ultraviolet rays from the outside world and prevent damage to the internal organs. Due to harsh natural conditions and lack of food, most species are adapted to scraping algae or feeding on benthic animals. Due to the cold climate, growth is extremely slow. Many species of 8-year-old fish only weigh 250 grams, 10-year-old fish weigh 500 grams, and those over 25 years old can reach a weight of 5,000 grams and a body length of 600 mm. Most species first become sexually mature at age 14 or above. Due to the long growth cycle and weak reproductive capacity, there are many raptors on the plateau. In order to protect themselves and their offspring, schizothorax fish have poisonous ovaries and testes, so other animals dare not swallow them rashly. In the past, Tibetans living on the Qinghai-Tibet Plateau did not eat fish and regarded fish as gods. The reason was related to the poisonous eggs of their fish.

The plateau loach schizothorax has a characteristic that is obviously different from other fishes, which is that there is a row of deformed large scales on both sides of the anus and the base of the anal fin, called anal fins. The presence or absence of scales on the body surface of schizothorax fishes is related to their distribution altitude. They can be roughly divided into three groups: the first group is the primitive level. The scales of the fish are covered all over the body or partially degraded. They have 2 pairs. This group lives in high altitudes. 1250-2500 meters above sea level; the second group is a specialized level, with partial or complete degeneration of body scales, and requires 1 pair, and lives in an altitude of 2750-3750 meters; the third group is a highly specialized level, with all body scales degenerating, and no need , inhabiting the area between 3750-5000 meters above sea level, among which small-headed plateau fish are distributed in water bodies with an altitude of 5100 meters.

Except for a few species, most of the other groups that accompany Schizothorax fishes are only 50-60 mm or more than 100 mm long. They usually inhabit the bottom of still water or slow flowing rivers and lakes, feeding on aquatic invertebrates or algae. Its distribution is similar to Schizothorax, with advanced specialized groups mainly distributed in the center of the plateau and the upper reaches of rivers. The more primitive taxa are mainly distributed on the edge of plateaus or low mountain canyon areas. Most species show broader adaptability to plateau environments. Five of them are distributed at altitudes of 5,000-5,200 meters above sea level, making them the most widely distributed fish on earth, far exceeding the record of 4,800 meters as the critical line of fish distribution proposed by American biologists.

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