chromatophores

Chromatophores are pigment-containing and light-reflecting cells that reside in the skin of many animals. They contribute to coloration by changing the size, distribution, or optical properties of pigments and reflective arranged structures, enabling rapid adaptive color patterns used in camouflage, signaling, and mate choice.

Across animals, chromatophores take different forms. In cephalopods such as squids, octopuses, and cuttlefish, chromatophores are muscular pigment sacs under neural control, layered with iridophores and leucophores that create iridescent and white reflections. In vertebrates, chromatophore-like cells include melanophores (melanin), xanthophores and erythrophores (carotenoids and pteridine pigments), as well as iridophores and leucophores in the skin. In many amphibians and reptiles, pigment cells contribute to dermal coloration, while some invertebrates and crustaceans use similar cells for color changes.

Mechanisms differ by lineage. In cephalopods, rapid color change results from nerve signals triggering expansion or contraction of pigment sacs, combined with light reflection from underlying reflective cells, allowing dynamic patterning in milliseconds. In vertebrates, pigment granules within chromatophores disperse or aggregate in response to neural or hormonal cues, altering visible color over seconds to minutes.

Functions include camouflage, disruptive or countershading patterns, social signaling, mating displays, and species recognition. The evolutionary development of chromatophores has produced some of the most sophisticated camouflage systems, particularly in cephalopods, and rapid color change is a distinctive adaptive trait in several marine lineages.