SEXUAL DICHROMATISM AND TEMPORARY COLOR CHANGES IN THE REPRODUCTION OF FISHES

Studies on color patterns of ashes have hocused on relationships betwe en bright, relatively permanent: colors, such as those of fishes inhab iting coral reef and tropical freshwater habitats, and ecological fact ors, such as competitors, predators, and the visual background. By com parison, the functions of, and hence the selective pressures acting on , temporary changes in nuptial coloration have received much less atte ntion. Temporary color changes associated with reproduction occur in m any freshwater and marine groups. Nuptial coloration in fishes functio ns both in agonistic interactions among males and courtship of females , so that it is subject to both intrasexual and intersexual selection as web as natural selection. Temporal variation in nuptial color patte rns is sensitive to temporal changes ire the male's physical condition , motivation, and social status. Physiological processes, such as neur onal and endocrine changes, play important roles in the expression of breeding colors, including rapid responses to changes in social condit ions. The importance of proximal mechanisms and ultimate selective pro cesses in mediating rapid changes in the blue, melanin-based breeding colors of pupfish, and the red, carotenoid-based color patterns in gup pies are discussed in the context of signal function and evolution.