benefits of being gold: behavioral consequences of polychromatism in the midas cichlid, Cichlasoma citrinellum

The midas cichlid, C. citrinellum , occurs in the lakes of Nicaragua. In semi-turbid to turbid lakes about 8% of the adults are amelanic, having lost their melanophores at various ages, and are thus yellow through red and sometimes white. The commonest hues are yellow through orange, called gold. Gold morphs ought to be selected against because they are probably conspicuous to predators and they cannot communicate by changing markings. To maintain the polymorphism, gold coloration must have offsetting advantages. Gold morphs dominate normal ones of equal size, and that improves their access to limiting resources. Gold morphs, however, do not seem to be intrinsically more aggressive but rather attain dominance through the effect of their color on their opponents.