(CNN)The Invisible Man isn't the only expert in making himself imperceptible with optics science. Species of ultra-black fish also have that tactic down pat, according to a study published Thursday in the journal Current Biology.
This pitch-black fish of the deep has a disappearing act scientists just solved
To fend off predators, fish wield common camouflage strategies such as transparency and mirrored surfaces. These methods are successful in shallower waters, through which sunlight easily penetrates.
However, at more than 650 feet deep into the ocean — in the lower mesopelagic and bathypelagic zones — there is little sunlight. So in these areas, evolutionary adaptations such as transparency and mirrored surfaces aren't as useful at keeping away assailants looking for dinner. That's because fish that use these defense strategies reflect at least 0.4% of bioluminescence from other deep-sea animals — which describes the production and emission of light by a living organism.
Pigmentation is another method for being incognito in the sea; it allows animals to absorb light from bioluminescent sources and thus become visually undetectable instead of reflecting that light off of themselves.
Karen Osborn, a research zoologist with the Smithsonian's National Museum of Natural History, thought to take a closer look at fish skin when she tried to photograph black fish she and her colleagues caught in Tucker trawl nets in the Gulf of Mexico and in Monterey Bay, California. Tucker trawl nets allow scientists to catch fish from mid-water levels, where ultra-black fish can be found. Regardless of the quality and arrangement of her camera and lighting, Osborn couldn't capture any detail in the shots.