The Origin and Evolution of Cave Fishes

Scientists have shown through extensive research that cave fish originated from ancestors that lived on the ground and partially adapted to the cave environment. They survive without sunlight, green vegetation and interspecific competition. When species on the surface enter the cave, the eyes become useless, and then gradually shrink and shrink until they disappear completely, leaving only fat-filled eye sockets. Some blind fish, such as the blind medaka in the United States, still have normal eyes in their juvenile stage. The naked-bellied medaka in Gejiu, Yunnan still has an eye spot the size of a pinhole in its right eye. This proves that blind fish have normal eyes on the surface. evolved from fish. Also due to the lack of light, the pigment used to prevent damage to internal organs from strong ultraviolet radiation from the sun fades away, so the body becomes translucent, and the internal organs and bones are vaguely visible.

In order to compensate for the decline of vision, the tactile organs have become particularly important and developed. Fish use the lateral line system to sense the oscillation waves of the external environment, allowing them to avoid obstacles and swim freely in turbid water or dark environments. In addition to strengthening the original lateral line of blind fish, other sensory organs also tend to be particularly developed. In killifish, the small protrusions on the head and body are arranged very regularly. In species with eyes, these protrusions are very regular. It is underdeveloped, but in the completely blind species it can be developed to the extreme. The protrusions can sense their own movements in the water, allowing them to avoid obstacles and explore where food is. Interestingly, fish with eyes that live in caves rarely rely on vision to find food. If their eyes are removed, they can quickly explore the location of food just like when they have eyes.

Experiments have shown that the taste, smell and hearing of this fish are exactly the same as those of other fish, and the only remedy for the loss of vision is the sensitivity of the lateral line. The cave-dwelling fish that have been discovered in my country all have 2 or 3 pairs of extremely developed tentacles. The 3 pairs of tentacles of Gejiu blind loach have different receptors and contain a large number of taste buds and cell processes. Yiliang's eyeless goldfish The linen barbel has special sensory lines on its head. The Cuban blind fish has many thin sensitive barbels, and the American blind goblin has many epithelial receptors. They rely on these unique structures to provide favorable guarantees for exploring food, finding mates and controlling their own actions in the dark. Another change in the characteristics of cave fish is that the scales of scaly species shrink, become sparse and scattered, and are finally completely buried under the skin. This may be due to the weakened activity of cave fish and gradually being covered by thickened skin.

Generally speaking, for fish that are accustomed to living in dark places and adapted to this environment, since they invaded caves, their descendants have gone deeper and deeper into dark caves, and have become more specialized the longer they live in dark caves. .

The value of cave fish cannot be measured based on traditional food or delicacy standards, and there is no economic value based on the amount of resources. As an example of the adaptation of organisms to the environment, it is a rare treasure in scientific research, intuitive teaching in schools and popular science displays in museums. Studying the evolution of cave fish helps us understand speciation. In practice, based on the dependence of fish life cycle activities on water, cave fish may become indicator organisms for finding underground water sources and monitoring water quality changes, opening up a new way to promote agricultural production and human environmental research.

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