![]() ![]() After the fish had adapted to a “neutral,” beige-colored fine gravel floor in a holding tank ( b), we moved them into small experimental tanks that each had different patterns on their floors. ![]() We obtained six specimens from an aquarist. Gregory and Chandramani Ramachandran, we therefore decided to experiment with the tropical reef flounder Bothus ocellatus, commonly known as the eyed flounder. It occurred to us that this fact could account for the poor show put on by Saidel’s flounder, which would not have had the evolutionary pressures to adapt to a greater range of backgrounds unlike the cold-water locations, the tropical environment contains more varied surfaces. So, he argued, in a sense it was the viewer’s eye that was doing the blending-not the flounder itself.Ĭold-water flounder live in a rather drab, monotonous sandy environment. Saidel claimed that the markings on flounder changed only slightly but that they had a kind of “universal” texture that allowed them to blend in with most backgrounds. Saidel, now at Rutgers University at Camden. But they were later challenged by neurobiologist William M. Sumner’s findings made a big splash when he published them. Mast, who in the early 20th century showed that the matching depends on vision blinded flounder do not change. Sumner’s work was supplemented by the experiments of S. Sumner, one of the founders (but not the sole flounder) of the Scripps Institution of Oceanography, showed nearly a century ago that cold-water flounder have an amazing capacity to match the “graininess” of their skin surface markings with gravel or pebbles in their background. Although chameleons are often credited with this skill, they are actually quite bad at it most of their color changes are reserved mainly to attract mates and protect their territories and are thus unrelated to camouflage.īiologist Francis B. Yet as the saying goes, “fact is stranger than fiction.” Some animals, such as cuttlefish, octopuses and flounder, can alter their markings and hues to suit whatever surface they happen to land on. To modern scientists, Thayer obviously got a bit carried away. But then he went on, even suggesting that peacocks’ tails match foliage and that flamingos are pink to allow them to blend in with the sunset ( a)! Studying the strategies of camouflage can therefore indirectly also tell us a great deal about the mechanisms of vision.Īmerican painter and amateur naturalist Abbott Handerson Thayer speculated that animals developed “protective coloration.” As his theory held, “animals are painted by nature darkest on those parts which tend to be most lighted by the sun’s light, and vice versa.” He was surely right about this effect (scientists now call it “countershading”). Indeed, we can almost think of higher visual processing in the brain as having mainly evolved to defeat camouflage. Not surprisingly, both prey and predators go to enormous lengths to conceal their physical boundaries by blending in with the color and texture of their surroundings. ONE OF THE MAIN FUNCTIONS of visual perception is to detect objects in the environment as a prelude to identifying them as prey, predators or mates. ![]()
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