I will repeat myself again, but i have to say it one more time – it is not easy to understand how natural selection works. Deep-sea species. One would expect, that so deep, where is no light, no eyes are needed at all. But not this time … Here, random mutations AKA unguided natural process achieved something really stunning and invented a super-vision. What sounds even more crazy, this miracle should have happened not once, but multiple times repeatedly and independently (because the species below are evolutionary not related).
Get ready for another just-so-story, this time from mainstream magazine at Sciencemag.org:
When the ancestors of cave fish and certain crickets moved into pitchblack caverns, their eyes virtually disappeared over generations. But fish that ply the sea at depths greater than sunlight can penetrate have developed super-vision, highly attuned to the faint glow and twinkle given off by other creatures.
Most fish have one or two RH1 opsins, like many other vertebrates, but four of the deep-sea species stood apart, the researchers report this week in Science. Those fish—the lantern-fish, a tube-eye fish, and two spinyfins—all had at least five RH1 genes, and one, the silver spinyfin (Diretmus argenteus), had 38. “This is unheard of in vertebrate vision,” says K. Kristian Donner, a sensory biologist at the University of Helsinki.
The four deep-sea species belong to three different branches of the fish family tree, indicating that this supervision evolved repeatedly. “This indicates that animals living in extreme light environments may be subject to extreme natural selective pressures to improve visual performance,” says Eric Warrant, a visual ecologist at Lund University in Sweden.
The finding “really shakes up the dogma of deep-sea vision,” says Megan Porter, an evolutionary biologist studying vision at the University of Hawaii in Honolulu who was not involved in the work. Researchers had observed that the deeper a fish lives, the simpler its visual system is, a trend they assumed would continue to the bottom. “That [the deepest dwellers] have all these opsins means there’s a lot more complexity in the interplay between light and evolution in the deep sea than we realized,” Porter says.
full article https://www.sciencemag.org/news/2019/05/deep-dark-ocean-fish-have-evolved-superpowered-vision