Pigmentation and color patterning of body and fins serve multiple functions in fish, including camouflage, communication, mate choice, or species recognition. Fish pigmentation is highly polymorphic and often sex-specific, particularly during the spawning season. Furthermore, many fish species change their pigmentation during their life cycle. Prominent examples for colorful fishes are coral reef fishes, poeciliids from Middle and South America (guppy, Poecilia reticulata; platyfish, Xiphophorus maculatus; swordtail, Xiphophorus hellerii) or the cichlids of the East African Great Lakes. (see also Vision: Color vision and Color Communication in Reef Fish) Coloration of teleost fishes is based on six different major types of pigment cells. Other fish lineages and tetrapods, in contrast, have a smaller repertoire of such chromatophores. Studying the genetic basis of fish coloration has a long tradition, particularly in East Asia, where color morphs of carp and goldfish have been cultured for more than 1500 years. In the beginning of the last century, poeciliids became popular among geneticists to study the inheritance of color patterns and also of pigment cell-derived tumors. The present article gives an overview of the types of pigment cells found in fish, the genetic control of their development and differentiation, and the genes that underlie color polymorphisms between natural fish populations. Subsequently, we discuss the longstanding interest in fish as model systems for the study of pigment cell-derived types of skin cancer.
