Just Trying to Fit In

Bothus ocellatus, a species of warm-water flatfish, is remarkably adept at camouflaging itself. Researchers at the University of California at San Diego have found that it can change big spots on its skin into small spots or squares, or even eliminate them altogether, if that’s what it takes to blend in with its surroundings and avoid predators. Neurologist Vilayanur Ramachandran and his colleagues placed a flatfish in a tank with a variety of patterns on the bottom, including large polka dots, yellow beach sand, and coarse gravel, shown here left to right. In each case, within eight seconds or less, the fish rapidly adapted its markings to closely match the pattern on the bottom. The fish accomplish their trick by using different combinations of clusters of pigmented bodies in their skin. By varying the dispersal of pigment, they use this palette to produce many kinds of patterns, Ramachandran says. Exactly how the fish recognize and re-create the background patterns is a mystery. Ramachandran suspects that there are specialized cells in their brains that can recognize particular patterns and then tell the skin what pigment bodies to expand or contract. There is probably a hot line from the vision center of the brain to the skin, says Ramachandran, to make these different textures in the skin to match the background.