In many species of fish, amphibians, crustaceans, and reptiles, melanosomes can be highly mobile within the cell in response to hormonal (or sometimes neural) control, which leads to visible changes in colour that are used for behavioural signaling or photoprotection.
The beautiful and rapid colour changes seen in many cephalopods such as octopuses and squid, are based on a different system, the chromatophore organ [REF].