[ad_1]
This discovery disrupts the "dogma of vision on the high seas", say the researchers.
The more you dive, the more light is scarce. As a result, vision is not really a primary attribute – and this happens in all dimly lit environments. In caves, for example, where light does not pass either, the eyes of fish (and other creatures) disappear after only a few generations. This makes a lot of sense: the eyes are "expensive" to produce and maintain, and if they are not motivated to use them, they could degrade and even disappear over time.
That's why the researchers were surprised to find that at least one species of deep-sea fish had excellent vision, able to capture a wide range of wavelengths and even see colors.
Researchers at the University of Maryland analyzed the genomes of 101 species, 13 of which had genes that allowed them to see in color. One species in particular, the silver spine, has a vast assortment of genes that allow it to capture different wavelengths of light.
"This is the first article to examine a diverse set of fish and see how versatile and variable their visual system can be," said Karen Carleton, professor of biology at the University of Maryland and co-author of the paper. "The genes that determine the light spectrum of our eyes are sensitive to become a much more variable set of genes, causing a greater evolution of the visual system much faster than expected."
The tube-eye fish, Stylephorus chordatus, can use five different opsins in his eyes. The long cylindrical shape of his eyes increases light capture and also allows the fish to move the eyes from a horizontal position to a vertical position. Image credit: Dr. Wen-Sung Chung, University of Queensland, Australia.
As we learned in school, cone cells are responsible for color vision, and stem cells are responsible for detecting brightness (especially in low light conditions). In this study, however, researchers found that this was not always the case. Sticks and cones contain light-sensitive pigments called opsins. These opsines absorb specific wavelengths and convert them into electrical signals that the brain can interpret. The number and type of opsins determine the colors that an animal can see.
They discovered that some fish contained several types of rod opsins, which suggests that they have a color vision based on the rods. In 99% of vertebrates, the rods express a type of opsine sensitive to light, which means that in low light conditions they are color-blind – which may not be the case for this fish. Silver spinach, for example, has a huge 38 opsin genes.
"It was very surprising," Carleton said. "This means that silver spiny fish have visual abilities that are very different from what we thought. The question is, what is it for? Why could these fish use these spectrally different opsines?
So, why do they need this ability? At a depth of more than 1,000 meters, where these creatures live, the last ray of sunshine has disappeared. Recent research, however, has refuted the traditional belief that there is no light at this depth. They have also shown that even at these depths, weak flashes of bioluminescence are sometimes visible. other fish.
Researchers believe that some fish may have developed better vision to detect certain types of prey or avoid their own predators.
"Their vision may be very attentive to the different light colors emitted by the different species they feed on," Carleton concludes.
The study "Vision using several different opsins in deep-sea fish" was published in Science.
[ad_2]
Source link