Carotenoid availability and tradeoffs in female convict cichlids, a reverse sexually-dichromatic fish

Abstract

Carotenoid pigments have myriad functions in fish, including coloration and immunity. The “carotenoid trade-off hypothesis” posits that dietary limitation of carotenoids imposes constraints on animals to allocate to one function at the expense of another. This hypothesis rarely has been tested in fish. We quantified tissue carotenoids in breeding and non-breeding female convict cichlids in Lake Xiloa, Nicaragua. This species is reverse sexually dichromatic such that females possess carotenoid-based coloration that males lack. We also collected algae samples near nest sites to assess carotenoid availability, recorded water depth, and examined cichlids’ behavioral interactions with pair mates, conspecifics, heterospecific competitors, and predators. Each of these, we predicted, would mediate potential carotenoid trade-offs. We found that non-breeding females had significantly higher levels of carotenoids in their integument, liver, and gonads compared to breeding fish. We found that algae and total carotenoids declined with depth across our study transects at 9, 11, 13, and 15 m, but the concentration of carotenoids (ng carotenoid g−1 algae, or algal quality) did not vary with depth. Furthermore, relationships among carotenoid concentrations of the three tissue types did not vary with depth, and female color status (orange or not) was not affected by behavioral interactions with other community members, reproductive status, or water depth. Our results support previous studies showing that carotenoid pigmentation may serve a signal function that facilitates the establishment of non-breeding females within the breeding population. Our study also uncovered no evidence indicating that carotenoids are limiting in the diet of breeding female convict cichlids.