Scientists have discovered ultra-black fish (numerous species) that absorb almost all light that hits them, allowing them to effectively hide in the deepest, darkest parts of the ocean. It appears to be a more efficient method than those used by other animals, and the find could help inform future advances in optical and camouflage technology.
The Pacific blackdragon is a fearsome-looking creature, and one of the ultra-black fish species described by the team
The discovery was made by a team led by scientists from the Smithsonian and Duke University. The fish were found to absorb 99.5 percent of all light, making them appear as little more than silhouettes even in direct light. And it wasn’t just one clever species either – the technique has so far been found in 16 different, distantly related species.
These fish were all found living at ocean depths below 200 m (656 ft), in the inky blackness beyond the reach of sunlight. Many animals have adapted to this environment by producing their own light, called bioluminescence, which can be used to attract food or mates, or to illuminate predators and prey hiding in the dark.
So for other species, blending in with the pitch-black background is an effective survival strategy. Absorbing almost every photon of light that hits you is a great way to boost your odds of both not being eaten, and not spooking your own food.
To investigate exactly how the fish manage to soak up light so effectively, the team closely examined specimens brought up from the deep in trawl nets. They found that the key was melanin, a light-absorbing pigment that also naturally darkens human skin to various degrees.
It turns out these fish have very high levels of melanin in their skin, and it’s arranged in a particularly special way. The pigment cells are made up of densely-packed compartments called melanosomes, which waste very little light thanks to their size, shape and positioning. What they don’t absorb themselves, they deflect to other melanosomes.
“Effectively what they’ve done is make a super-efficient, super-thin light trap,” says Karen Osborn, lead researcher on the study. “Light doesn’t bounce back; light doesn’t go through. It just goes into this layer, and it’s gone.”
“This is the only system that we know of that’s using the pigment itself to control any initially unabsorbed light,” says Osborn. “Instead of building some kind of structure that traps the light, if you were to make the absorbing pigment the right size and shape, you could achieve the same absorption potentially a lot cheaper and a lot less fragile.”
https://newatlas.com/science/ultra-black-fish-absorb-light/