Chromatophore

Chromatophores are cells that produce color, of which many types are pigment-containing 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 ectothermic animals and are generated in the neural crest during embryonic development. Mature chromatophores are grouped into subclasses based on their colour under white light: xanthophores (yellow), erythrophores (red), iridophores (reflective / iridescent), leucophores (white), melanophores (black/brown), and cyanophores (blue). While most chromatophores contain pigments that absorb specific wavelengths of light, the color of leucophores and iridophores is produced by their respective scattering and optical interference properties.

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.^[1] 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.^{[citation needed]} Chromatophores are studied by scientists to understand human disease and as a tool in drug discovery.