The study found that grass carp originated in western China 33 million years ago

◎ Reporter Lu Chengkuan of this newspaper

Grass carp is one of the four major fish in Freshwater aquaculture in China, and is sought after by many foodies because of its delicious meat. So, do you know when and where grass carp originated?

On November 2, the reporter learned from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences that researchers from the institute and other units found that grass fish may have originated from a carnivorous fish in western China in the early Oligocene 33 million years ago through a comparative study of the extinction of two extinction genera, species and two extinctions of grass carp from Inner Mongolia, Qinghai, Jiangsu and other places, as well as the fossil pharyngeal teeth of modern grass carp. At that time, although the climate in western China was probably drier than in the east, it still had suitable climatic conditions for grass carp to grow. Modern grass carp may have been formed in the Pliocene 5.3 million years ago. The research results were published in the English edition of Science in China: Earth Sciences in the form of a cover article.

The history of grass carp being eaten in China can be traced back to the Yin Shang period, and its current species are naturally distributed in eastern China, and they are called "pioneers" because of their ability to quickly remove various grasses from water bodies.

Grass carp have distinctive comb-shaped pharyngeal teeth. The surface of the pharyngeal teeth of grass carp is enamel and very hard. The old pharyngeal teeth wear out during continuous feeding, and then new pharyngeal teeth grow out to replace them. Su Ruifeng, an associate researcher at the Beijing Institute of Life Sciences of the Chinese Academy of Sciences, said: "The pharyngeal teeth buried in the formation after wear and tear have become a very valuable material for us to study the evolution of carps. ”

"After studying the fossils of the pharynx of two extinction genera and species of grass carp and two extinction species of grass carp found in many places, we speculate that grassfish originated from a carnivorous fish in western China in the early Oligocene 33 million years ago, when it was a temperate grassland environment, which was not much different from the habitat environment of grass carp today." Su Ruifeng said.

According to the grass carp or grass carp fossils found so far, from the late Oligocene to the Miocene, grass fish spread and migrated eastward, spreading throughout western, eastern and northern China, with a much wider distribution than that of modern grass carp. Since the Pliocene 5.3 million years ago, with the strengthening of the uplift of the Qinghai-Tibet Plateau, the large rivers flowing eastward into the Pacific Ocean in East Asia have formed, and with the strengthening of the Asian summer winds, the distribution of grass fish has finally been limited to the new environment on the east coast of the Pacific Ocean, evolving into a modern species, forming the current life and breeding habits.

In Su Ruifeng's view, the study of the fossil pharynx of grass fish broadens the understanding and understanding of the evolution of carps endemic to East Asia in time and space, and combines the life and reproductive habits of grass fish and the mammals unearthed at the same site, which can reflect the climate and water environment characteristics of the land point to a certain extent.

Among the great rivers in eastern China, the Heilongjiang and Yellow River systems have a variety of fish, and grass carp is also one of them. However, there is no record of grass carp in the Liao River system between these two major rivers. Researchers believe that it is likely that the Liao River once had a distribution of grass carp, when the Nen River was still upstream of the Liao River. In the Quaternary Period, the city of Changchun and its vicinity between the Nen river and the Liao River was uplifted by the new tectonic movement, and the upper reaches of the Gu Nen-Liao River were attacked by the Songhua River, a large tributary of the Heilongjiang River, thus bringing many fish, including grass carp, to the northern Heilongjiang River. When the Liao River is separated from the Nen River upstream, the amount and length of the Liao River are no longer suitable for grass carp to survive and reproduce.

Su Ruifeng said that the evolution of grass fish shows that in the Oligocene, although it was a little dry and cold in western China, it was still warmer than today; in the Miocene, the climate in central Inner Mongolia was also warmer and wetter than it is today; from the Pliocene onwards, the climate and water ecological environment in East Asia became similar to modern times.

Source: Science and Technology Daily