Almost a mile below the surface, in the lung-crushing abyss of the ocean, deep-sea fish move stealthily through their forever night. With their black skin absorbing nearly all of the light that strikes it, the fish — nearly impossible to see at depth — appear to cut a hole in reality, making them difficult to photograph even when brought to the surface.
"It didn't matter how you set up the camera or lighting — they just sucked up all the light," zoologist Karen Osborn of the Smithsonian National Museum of Natural History told Duke Today.
Researchers from Duke, the Smithsonian, and the Monterey Bay Aquarium Research Institute found that at least 16 species of deep-sea fish possess this kind of ultra-black skin. The skin, they write in Current Biology, has evolved as a unique form of camouflage for a unique environment.
In the midnight zone of the deep ocean, there's few places to hide. And while there's no sunlight that can give deep-sea fish away, there are light sources: bioluminescent organisms who create their own eerie light.
Typical forms of ocean camouflage, like being transparent or mirrored, would make a deep-sea fish rather conspicuous, the researchers write; in response, some deep-sea fish have gone the completely opposite direction, instead evolving ultra-black skin that sucks up — not scatters — light.
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The team pulled 39 black deep-sea fish from up to a mile beneath Monterey Bay and the Gulf of Mexico. Using a spectrometer, they identified 16 species that reflect less than .5% of light. These ultra-black fish, Duke Today says, are roughly 20x darker and less reflective than your typical black object.
"Ultra-black arose more than once across the fish family tree," Alexander Davis, a biology Ph.D. student at Duke and first author of the study, told Duke Today.
A tiny anglerfish, shorter than a pen cap, was the darkest deep-sea fish they found. The little fellow devoured light, reflecting back only .04% of light to the eye. Only one other type of animal can absorb light like this, Duke Today reports: the weird as hell birds-of-paradise from New Guinea, with their ultra-dark plumage. The fish out-pace ultra-black butterflies and (shudder) super-black jumping spiders.)
The deep-sea fish owe their camouflage to the structure of their skin, the researchers say. Both normal black and ultra-black skin contain minute structures in their cells, called melanosomes. These contain the melanin that gives the skin its color.
But the melanosomes of ultra-black fish are different than just normal black fish; under an electron microscope, the researchers found them to be larger and more tightly packed together.
Rather than the pearl-shaped, spaced-out melanosomes of other black-skinned, cold-blooded creatures, ultra-black deep sea fish have melanosomes that are more akin to Tic-Tacs, packed so tight they are nearly an unbroken veil.
Ultra-black deep-sea fish skin cells are "like a tiny gumball machine, where all of the gumballs are of just the right size and shape to trap light within the machine," Davis said.
It's sort of the natural equivalent of the nanotubes that absorb light for the freakishly dark pigment vantablack, or MIT's accidentally made, ten-times-darker material (responsible for one of my favorite pieces of art, Diemut Strebe's The Redemption of Vanity — someone buy it for me, please!).
The simple design and optimal shape of the ultra-black deep-sea fish skin cells may help inspire the creation of new, synthetic ultra-black materials, the authors write. Super light-absorbing materials could lead to improved solar panels and telescopes, among whatever other uses scientists — and artists — can dream up.
I, for one, am all for more fabric-of-reality hole cutting.