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Chromatophores are pigment-containing and light-reflecting cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, have a class of cells called melanocytes for coloration. Chromatophores are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development. Mature chromatophores are grouped into subclasses based on their colour (more properly "hue") under white light: xanthophores (yellow), erythrophores (red), iridophores (reflective / iridescent), leucophores (white), melanophores (black/brown), and cyanophores (blue). Some species can rapidly change colour through mechanisms that translocate pigment and reorient reflective plates within chromatophores. This process, often used as a type of camouflage, is called physiological colour change or metachrosis. Cephalopods such as the octopus have complex chromatophore organs controlled by muscles to achieve this, whereas vertebrates such as chameleons generate a similar effect by cell signalling. Such signals can be hormones or neurotransmitters and may be initiated by changes in mood, temperature, stress or visible changes in the local environment. Chromatophores are studied by scientists to understand human disease and as a tool in drug discovery. == Human discovery == Aristotle mentioned the ability of the octopus to change colour for both camouflage and signalling in his ''Historia animalium'' (ca 400 BC):〔Aristotle. ''Historia Animalium''. IX, 622a: 2-10. About 400 BC. Cited in Luciana Borrelli, Francesca Gherardi, Graziano Fiorito. ''A catalogue of body patterning in Cephalopoda''. Firenze University Press, 2006. (Abstract ) (Google books )〕 Giosuè Sangiovanni was the first to describe invertebrate pigment-bearing cells as ' in an Italian science journal in 1819.〔Sangiovanni G. Descrizione di un particolare sistema di organi cromoforo espansivo-dermoideo e dei fenomeni che esso produce, scoperto nei molluschi cefaloso. ''G. Enciclopedico Napoli''. 1819; 9:1–13.〕 Charles Darwin described the colour-changing abilities of the cuttlefish in The Voyage of the Beagle (1860): 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「Chromatophore」の詳細全文を読む スポンサード リンク
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