DISSERTATION RESEARCH: The food matrix mediates carotenoid tradeoffs in a reverse-dimorphic cichlid

Amherst College, Amherst MA

Investigators

Abstract

Most red, orange and yellow coloration in vertebrate animals is the result of carotenoid pigments. Vertebrates cannot synthesize carotenoids and instead must obtain them from their diet, but carotenoids also play important roles in reducing oxidative stress and supporting the immune system. The carotenoid trade-off hypothesis predicts that when dietary carotenoids are limited, animals must sacrifice coloration or immunity. Many published studies of the carotenoid trade-off hypothesis cite the assumption that dietary carotenoids are limiting, but this statement is largely untested. Likewise, little is known about carotenoid trade-offs in females of species with reversed sexual dichromatism, i.e. species in which females are more brightly colored than males. Females have an additional competing need for carotenoids, namely that the pigments can be incorporated into egg yolk and passed on to their offspring. This proposal seeks to use a combination of laboratory and field studies to understand the complex relationship between carotenoid absorption, sexual coloration, and somatic maintenance in pigmented females by developing a statistical model to predict carotenoid availability and allocation in the wild. The proposed study will address these questions using the convict cichlid (Amatitlania nigrofasciata), a well-studied Central American fish in which females have carotenoid-based ventral coloration. The proposed study would use field work to design a simultaneous equations model on which to base future laboratory studies of the interaction between environmental carotenoid availability and the food matrix in carotenoid-pigmented species. Development of a statistical model for carotenoid absorption will allow other researchers to place their work on the carotenoid trade-off hypothesis into a theoretical context, in addition to having implications for fish health in ornamental and food fish farming, both multi-million dollar industries in the United States.