Protogynous sexuality and gonad structures in the coral-dwelling goby Pleurosicya mossambica

Coral reefs are one of the most species-rich environments. Various habitat-specialist gobies are known to exhibit labile sexual patterns as an adaptive strategy to narrow econiches. In this study, the habitat use, social group composition, and gonad structure of the coral-dwelling toothy goby Pleurosicya mossambica were investigated on the reefs of Kuchierabu-jima Island, southern Japan, by field sampling and histological observation of their gonads. The goby was found to inhabit both hard and soft corals. Males were larger than females, and a sexually transitional individual was confirmed. These results suggest a possibility of protogynous sexuality in P. mossambica . Females exhibited ovaries with precursive accessory gonadal structures, whereas males had testes with accessory gonadal structures. This type of gonad structure was reported in phylogenetically different groups of protogynous gobies, suggesting that the same gonad structures may evolve independently in Pleurosicya species.