Sex Change in the Damselfish Dascyllus Reticulatus (Richardson) (Perciformes: Pomacentridae)

Dascyllus reticulatus, the two-stripe or reticulated damselfish, is shown to be a protogynous hermaphrodite on the basis of the histology of its gonads. Small females have no apparent presumptive testicular tissues but older females show various degrees of proliferation of spermatogenic crypts (=cysts), and oocyte remnants are visible in all but the largest males. Males retain the ovarian lumen and a separate sperm duct develops in the gonad wall. There is no evidence for prematurational sex change in this species. Small transitional fish were present within each group examined, and in all but one case they were smaller than the largest females in their groups. Their presence may be the consequence of a strategy by which such individuals gain some reproductive advantage. We suggest as one possibility that they become the dominant males in groups of smaller conspecifics, including groups newly-settled from the plankton which presumably lack males.