“outside fish” in the deep sea

  We call the ocean more than 1000 meters deep into the deep sea. At this depth, there is basically no trace of sunlight, and it is black and white all the year round. Living in such an environment, deep-sea fish are mostly “scorpions” with degraded eyes. This is our long-standing understanding of deep-sea fish. But a recent study showed us the other side of the coin: deep sea fish also have long eyes.
  Most of the deep-sea fish are strange, such as the big fins and the anus fish with a transparent head and tubular eyes. These eyes grow on the top of the head, can move up and down and left and right and adjust the focal length so that it can look straight ahead. Or look up, like a telescope protruding from a submarine. These eyes are not only very special in structure, but also have the ability to distinguish colors more than the eyes of most animals.
  Usually, the color vision of an animal is achieved by the interaction of various photosensitive pigments in the photoreceptor cells of the retina. Each of these photoreceptors reacts to light of a specific wavelength, but color vision can only be formed during the day. In the dark environment, the number of light particles is very small. These light particles can only react to one type of photopigment, rhodopsin, which allows the animal to see the outline of the object but not the color of the object. All animals are color blind in dark environments.
  However, some deep-sea fish are the exception. Recently, zoologists have discovered that some deep-sea fish have multiple genes that regulate rhodopsin, big fin rear anal fish, glacier lantern fish, long-winged spiny fin fish and silvery fins. The deep-sea fish contains more than 5 RH1 genes that regulate rhodopsin, and the RH1 gene of silver-filled fins is as many as 38! Humans only have one RH1 gene. Scientists have found that mutations in multiple sites of the RH1 gene have resulted in new rhodopsin in the deep-sea fish with the RH1 gene, which is different from our known rhodopsin. Rhodopsin recognizes blue and green light in dark environments.
  So, what is the use of a pair of discernible eyes in the dark deep sea? In fact, in the deep sea, the mysterious light flashes from time to time, and the squid’s dorsal fin is specialized into a small light bulb that grows on top of its head; the shark’s body skin is spread with melanocytes, which can emit green phosphorescence; The creatures can rely on symbiotic luminescent bacteria, such as light from luminescent bacteria attached to the squid. These fish glow, some are tempting prey, like a small light bulb on the top of a squid, and some are scaring predators.
  For such light, if the deep-sea fish has a pair of telescope-like eyes, you can see the potential prey or predator, you can take the initiative to attack or avoid in time, which obviously can live better in the deep sea.
  Although most of the deep-sea fish are strange and look like alien creatures, in-depth study of the physiological structure of deep-sea fish can also provide some protection for our space exploration journey, especially the ability of deep-sea fish to distinguish colors in the dark. Maybe it can help us survive in the dark alien planet!