THE IMPORTANCE OF CAROTENOIDS IN SIGNALING DURING AGGRESSIVE INTERACTIONS BETWEEN MALE FIREMOUTH CICHLIDS (CICHLASOMA-MEEKI)

Male firemouth cichlids, Cichlasoma meeki, have red pigmentation cover ing large areas of their ventral surface, which is displayed during ag gressive interactions. We manipulated the levels of red pigmentation b y assigning the fish to one of two diets, which were as similar as pos sible except that one was high in carotenoids while the other was low in carotenoids. During diadic trials under white light, fish kept on t he high carotenoid diet won a higher proportion of contests than fish kept on the low carotenoid diet. Under green light, where differences in redness cannot be discriminated, there was no effect of diet on the outcome of contests. These experiments demonstrate that it is the eff ect of the diet on red pigmentation that is important rather than some confounding variable such as differential growth rates. The weight of the two fish was also important; there was a tendency for the heavier fish to win more contests. The mass effect was subordinate to color u nder white light but was the dominant factor under green light. The na ture of the contests under the different light conditions also varied; the display in which the red pigmentation is most obvious was not use d under green light, but was common under white light. This suggests t hat the display strategies are flexible and can be altered according t o which displays are most effective in a given environment. Previous s tudies of other species of fish and birds have shown that the degree o f redness influences mate choice and is affected by parasite infestati ons. We propose that carotenoid pigmentation is likely to reflect a ge neral quality influenced by several factors, rather than a context-spe cific quality such as fighting ability.