By Will Dunham
WASHINGTON (Reuters) – For fish that inhabit the immense darkness of the deep sea, being ultra black offers great camouflage in a fish-eat-fish world. Scientists studying some of these exotic creatures have now deciphered the secret behind their extreme color.
These fish, such as fang tooth, Pacific black dragon, monkfish, and black swallower, have altered the shape, size, and packaging of the pigment in their skin to the point that it reflects less than 0.5% of light. hitting him, investigators said Thursday.
They studied 16 species that fit this definition of ultra black. These spanned six different orders of fish, large groups having a shared evolutionary history, indicating that this modification evolved independently in all of them.
“In the deep, open ocean, there is nowhere to hide and many hungry predators,” said zoologist Karen Osborn of the Smithsonian Institution’s National Museum of Natural History in Washington, co-author of research published in the journal Current Biology. . “An animal’s only option is to blend into the background.”
Very little sunlight penetrates more than 650 feet (200 meters) below the ocean surface. Some of these fish reside three miles (5,000 meters) deep.
At such depths, bioluminescence (light emission by living organisms) is the only light source. Some of the ultra black fish have bioluminescent lures on their bodies to convince their prey close enough to be eaten.
The skin of these fish is among the blackest material known, as it absorbs light so efficiently that even in bright light they look like silhouettes, as Osborn discovered when trying to photograph them after they were brought to the surface.
The melanin pigment is abundant in this skin and is distributed in an unusual way. By packaging melanosomes of perfect size and shape (pigment-filled structures within skin cells) in tight, continuous layers on the skin’s surface, the fish ensure that essentially all of the light reaching them reaches this layer and never escape.
“This mechanism of making thin and flexible ultra black material,” said Osborn, “could be used to create ultra black materials for high-tech optics or for camouflage material for night operations.”
(Reporting by Will Dunham; Sandra Maler’s Edition)
