Researchers have discovered one of the blackest materials on Earth – material that reflects less than .5 percent of the light that hits it – on the skin of deep-sea fish that use their blackness as camouflage from predators.
The fish's skin and its possible applications in the above-water world are described in a study published Thursday in the science journal Current Biology. The lead author of the study, Smithsonian Natural History Museum zoologist Karen Osborn, said in her research she kept coming across black fish that she could not quite photograph — she could only capture their silhouette.
This inspired her to capture samples of the fish and examine them. Deep-sea fish of this nature, she said, use their blackness to escape predators. In their environment, where sunlight cannot reach, many fish have developed bioluminescence — their own biological light source — which they use to hunt their prey. Their prey, in turn, evolved their blacker-than-black skin.
Osborn found the fish had developed a unique arrangement of melanin — the pigment in skin — concentrated in a thin layer near the skin's surface. It is so concentrated, she said, that it prevents light from leaving the layer of skin. This quality allows the fish to be invisible to predators and their own prey alike.
The study indicates there are 16 species of fish, some totally unrelated, with this blackness trait in their skin. The researchers said their findings could have practical applications in designing telescopes, cameras and camouflage for humans and their equipment.