LAUSR

Red carotenoid-based coloration is widely distributed across marine and terrestrial animals and has taken a prominent role in studies of how phenotypic traits evolve in response to natural and sexual selection. Key to these studies is an understanding of the physiological mechanisms involved in the production of red coloration, yet a model laboratory system for such work is lacking. The marine copepod Tigriopus californicus is used as a model for studies in ecotoxicology, genetics and physiology, but the mechanisms involved in the production of its bright red coloration have not been well studied. Like nearly all animals that display red carotenoid coloration, T. californicus likely convert yellow carotenoids present in their algal diet to red carotenoids. We conducted precursor/product feeding experiments to demonstrate that T. californicus bioconverts dietary carotenoids to the red carotenoid, astaxanthin. Copepods were fed carotenoids that are precursors to specific astaxanthin bioconversion pathways. We found that copepods from each precursor pigment group produced astaxanthin, and that the amount produced depended on which carotenoid was supplemented.