Unique genetic adaptation allows deep-sea fish to see color in the dark

WASHINGTON (Reuters) – While humans and other vertebrates are color-blind in subdued light, some deep-sea fish might have good color vision and thrive in the near total darkness of their extreme environment thanks to a unique genetic adaptation, scientists said Thursday.

The researchers analyzed the genomes of 101 species of fish and discovered that three deep water fish lines, living at about 1500 meters altitude, have a specialized visual system allowing for a vision. colors in the dark.

Having an acute vision could provide huge benefits to these fish seeking food and partners and trying to avoid becoming another creature's dinner in the dark and exotic seabed world, the largest habitat of the planet.

"Their eyes are certainly much more sensitive, so we think their vision in the depths would be very good," said evolutionary biologist Zuzana Musilova of the Charles University of Prague, one Researchers from the study published in the journal Science.

Vertebrates use two types of photoreceptor cells in the retina: light-sensitive rods and cones. Cones are used in bright light conditions and perceive colors. The stems are used in low light conditions, not designed to detect colors.

Stick cells contain a single type of photopigment – pigments that react at a certain wavelength of light – called rhodopsin. The researchers found 13 species belonging to the three deep-water fish lines showing a proliferation of rhodopsin-controlling genes, apparently leaving them to use rods to detect the colors. One species, silver spruce, had 38 copies of the rhodopsin gene, rather than the ordinary one.

The spruce, with shiny silver body, has an almost circular shape and big eyes. Other fish with this visual system include the elongated tube eye fish and the bioluminescent lantern fish.

"They are most likely able to see the color only with the help of stems, which is unique among vertebrates," said Musilova.

These fish are small and measure up to 30 cm long. They eat plankton and shrimp at depths between 400 and 200 meters.

The residual surface light is approximately 1,000 meters (six tenths of a mile). Light also emanates from common bioluminescent creatures in deep oceans, including monkfish, which has a bright lure attached to its head to attract prey.