Chromatophore
animal cells that produce color, of which many types are pigment-containing cells / From Wikipedia, the free encyclopedia
Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye color in cold-blooded animals.
Some species can rapidly change color so as to keep in camouflage, or to signal. They do this by moving pigment and reflective plates in chromatophores. This process is called physiological color change. Cephalopods such as octopus have complex chromatophore organs controlled by muscles to achieve this. The display is under central nervous control based usually on input from the eyes.
Vertebrates such as chameleons get a similar effect by cell signalling. Such signals can be hormones or neurotransmitters. They may be started by changes in mood, temperature, stress or visible changes around the animal.