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Counter-illumination is a method of camouflage in which an animal (or possibly a military vehicle) produces light to match an illuminated background, such as the ocean surface or sky. It differs from countershading which uses only pigment, such as a vehicle's paint or the melanin in an animal's skin, to paint out the appearance of shadows. By adding the right amount of light through bioluminescence or electronically controlled lamps, counter-illumination can at best exactly match the brightness of the background, making for more effective camouflage than countershading can provide. Since counter-illumination allows the intensity of the generated light to be adjusted, camouflage can be actively adapted to varying lighting conditions and backgrounds. Counter-illumination is one of the dominant methods of camouflage in marine organisms, along with transparency and silvering. All three methods make animals in open water resemble their environment. == Principle == Among marine organisms, counter-illumination camouflage occurs where bioluminescent light from an organism's ventral surface〔Young. R.E, Roper. C.F.E. 1977. Intensity Regulation of Bioluminescence during Countershading in Living midwater animals. Science, New Series. Vol 191,4231: 1046-1048.〕 is matched to the light radiating from the environment. The bioluminescence is used to obscure the organism's silhouette produced by the down-welling light.〔Jones(2004): p.1151〕 Some midwater cephalopods, decapod crustaceans, and fishes utilize this form of camouflage.〔Jones(2004): Young 1977, as cited by Jones et al. 2004〕 The bioluminescence used for Counter-illumination can be either autogenic (produced by the animal itself) or bacteriogenic (produced by bacterial symbionts).〔(Jones et al. 2004)〕 The luminescent bacterium is often ''Aliivibrio fischeri''.〔Jones. B.W, Nishiguchi. M.K. 2004. Counterillumination in the Hawaiian bobtail squid, Euprymna scolpes Berry (Mollusca: Cephalopoda). Marine Biology. 144:1151-1155.〕 Reducing the organism's silhouette is primarily an anti-predator defence for mesopelagic organisms. The reduction of the silhouette from highly directional down-welling light is important as there is no refuge in the mesopelagic, and predation occurs from below.〔Young. R.E, Roper. C.F.E. 1976. Bioluminescent countershading in Midwater Animals from living Squid. Science, New Series. Vol 191,4231: 1046-1048.〕〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Counter-illumination」の詳細全文を読む スポンサード リンク
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