Is the world in the eyes of deep-sea fish as colorful as humans?

For deep-sea fish, many people probably have the stereotype of "just grow as long as you want" and "it's dark and you can't see it anyway". However, a paper recently published in Science pointed out that some deep-sea fish can not only see, but also have the ability to distinguish colors. What is even more surprising is that the realization mechanism of their color vision is not quite the same as ours.

Physiological knowledge tells us that vertebrates have one of the most advanced visual systems on earth, and fish is no exception. Our eyes are almost a high-definition digital camera: in front of the eyeball, the lens protected by the cornea is a convex lens, which refracts the light entering the pupil to the back of the eyeball; Subsequently, this beam of light, which describes everything in our field of vision, changes from a light signal to a neuroelectric signal on the retina of the posterior wall of the eyeball and enters our brain for further processing.

Different opsins are encoded by different gene sequences in the genome, and their sensitivity to light with different wavelengths (that is, "colors") is also different. On the retina of vertebrates, there are two main types of photoreceptor cells: the head of rod cells is a long cylinder, and the opsin contained is rhodopsin, which is most sensitive to blue-green light. The head of cone cells is conical, and each cone cell contains a opsin sensitive to blue light, green light or red light.

The so-called "different rhodopsin" means that the amino acid sequence of these protein "variants" has changed, and as a visual protein, the sequence change is likely to lead to different "sensitive regions". Sure enough, by synthesizing rhodopsin in vitro, the researchers found that these different varieties were sensitive to different wavelengths of light, ranging from blue light of 447 nm to yellow-green light of 513 nm. This means that these rhodopsin varieties in the rod cells of the silver-eyed porgy may be able to distinguish colors like various opsins in cone cells of other vertebrates.