Female coloration and egg carotenoids in gobies

In the two-spotted goby (Gobiusculus flavescens), sexually mature females develop orange belly coloration that is used in female courtship displays. The degree of coloration varied greatly among individuals, and males strongly prefer females with more colourful bellies. We quantified female belly coloration from digital photographs, and determined gonad/clutch carotenoid concentration by HPLC. Both gonad carotenoid concentration and belly coloration increased as the females approached maturity, but coloration also varies greatly among females that are ready to spawn. Belly coloration was positively related to the carotenoid concentration both in gonads and in laid eggs. Since the abdominal skin is highly transparent, belly coloration seems to be a direct and reliable indicator of the carotenoid levels in the gonads. We quantified the quality of eggs and larvae both in females naturally varied in belly coloration and in females fed different amounts of carotenoids. Naturally drab females produced offspring that hatched and survived to the same degree as naturally colorful females. Likewise, females fed a diet low in carotenoids produced offspring that hatched and survived to the same degree as females fed a high-carotenoid diet. Therefore, egg carotenoid concentration did not seem to affect hatching success and larval viability. In a study measuring the phototactic response of newly hatched larvae, however, larvae from females fed a low-carotenoid diet were less efficient in swimming toward a light source.