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Animal coloration is the general appearance of an animal resulting from the reflection or emission of light from its surfaces. Some animals are brightly coloured, while others are hard to see. In some species, such as the peacock, the male has strong patterns, conspicuous colours and is iridescent, while the female is far less visible. There are several separate reasons why animals have evolved colours. Camouflage enables an animal to remain hidden from view. Signalling enables an animal to communicate information such as warning of its ability to defend itself (aposematism). Animals also use colour in advertising, signalling services such as cleaning to animals of other species; to signal sexual status to other members of the same species; and in mimicry, taking advantage of another species' warning coloration. Some animals use colour to divert attacks by startle (deimatic behaviour), surprising a predator e.g. with eyespots or other flashes of colour, and possibly by motion dazzle, confusing a predator's attack by moving a bold pattern (such as zebra stripes) rapidly. Some animals are coloured for physical protection, such as having pigments in the skin to protect against sunburn, while some frogs can lighten or darken their skin for temperature regulation. Finally, animals can be coloured incidentally. For example, blood is red because the haem pigment needed to carry oxygen is red. Animals coloured in these ways can have striking natural patterns. Animals produce colour in different ways. Pigments are particles of coloured material. Chromatophores are cells containing pigment, which can change their size to make their colour more or less visible. Some animals, including many butterflies and birds, have microscopic structures in scales, bristles or feathers which give them brilliant iridescent colours. Other animals including squid and some deep-sea fish can produce light, sometimes of different colours. Animals often use two or more of these mechanisms together to produce the colours and effects they need. ==History== Animal coloration has been a topic of interest and research in biology for centuries. In his 1665 book ''Micrographia'', Robert Hooke describes the "fantastical" (structural, not pigment) colours of the Peacock's feathers:〔Hooke, R. Micrographia. Chapter 36 ('Observ. XXXVI. ''Of Peacoks, Ducks, and Other Feathers of Changeable Colours''.').〕 According to Charles Darwin's 1859 theory of natural selection,〔Darwin, C. 1859〕 features such as coloration evolved by providing individual animals with a reproductive advantage. For example, individuals with slightly better camouflage than others of the same species would, on average, leave more offspring. In his ''Origin of Species'', Darwin wrote:〔Darwin, C. 1859, chapter 4〕 Henry Walter Bates's 1863 book ''The Naturalist on the River Amazons'' describes his extensive studies of the insects in the Amazon basin, and especially the butterflies. He discovered that apparently similar butterflies often belonged to different families, with a harmless species mimicking a poisonous or bitter-tasting species to reduce its chance of being attacked by a predator, in the process now called after him, Batesian mimicry.〔Bates, 1863.〕 Edward Bagnall Poulton's strongly Darwinian 1890 book ''The Colours of Animals, their meaning and use, especially considered in the case of insects'' argued the case for three aspects of animal coloration that are broadly accepted today but were controversial or wholly new at the time. It strongly supported Darwin's theory of sexual selection, arguing that the obvious differences between male and female birds such as the Argus pheasant were selected by the females, pointing out that bright male plumage was found only in species "which court by day".〔Poulton, 1890. pp331-334.〕 The book introduced the concept of frequency-dependent selection, as when edible mimics are less frequent than the distasteful models whose colours and patterns they copy. In the book, Poulton also coined the term aposematism for warning coloration, which he identified in widely differing animal groups including mammals (such as the skunk), bees and wasps, beetles, and butterflies.〔Poulton, 1890.〕 Frank Evers Beddard's 1892 book, ''Animal Coloration'', acknowledged that natural selection existed but examined its application to camouflage, mimicry and sexual selection very critically. The book was in turn roundly criticised by Poulton. Abbott Handerson Thayer's 1909 book ''Concealing-Coloration in the Animal Kingdom'', completed by his son Gerald H. Thayer, argued correctly for the widespread use of crypsis among animals, and in particular described and explained countershading for the first time. However, the Thayers spoilt their case by arguing that camouflage was the sole purpose of animal coloration, which led them to claim that even the brilliant pink plumage of the flamingo or the roseate spoonbill was cryptic — against the momentarily pink sky at dawn or dusk. As a result, the book was mocked by critics including Theodore Roosevelt as having "pushed ("doctrine" of concealing coloration ) to such a fantastic extreme and to include such wild absurdities as to call for the application of common sense thereto."〔Thayer, 1909.〕 Hugh Bamford Cott's 500-page book ''Adaptive Coloration in Animals'', published in wartime 1940, systematically described the principles of camouflage and mimicry. The book contains hundreds of examples, over a hundred photographs and Cott's own accurate and artistic drawings, and 27 pages of references. Cott focussed especially on "maximum disruptive contrast", the kind of patterning used in military camouflage such as disruptive pattern material. Indeed, Cott describes such applications:〔Cott, 1940.〕 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「Animal coloration」の詳細全文を読む スポンサード リンク
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