Fish Have Evolved Super-Vision In The Deep Sea’s Pure Darkness

Source: Science/Elizabeth Pennisi

Photo: Dr. Ken Sulak/USGS/NOAA/Wikimedia Commons

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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. They owe this power, evolutionary biologists have learned, to an extraordinary increase in the number of genes for rod opsins, retinal proteins that detect dim light. Those extra genes have diversified to produce proteins capable of capturing every possible photon at multiple wavelengths—which could mean that despite the darkness, the fish roaming the deep ocean actually see in color.

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.

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Photo: Dr. Ken Sulak/USGS/NOAA/Wikimedia Commons

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