Seasonal and length group based changes in the development of gonads and Light Organ (LO) were studied in orangefin ponyfish, Photopectoralis bindus. Light organ shows sexual dimorphism with males having larger LO compared to conspecific females belonged to the same length group. Gonadosomatic Index (GSI) and Percentage Light organ weight (PLW) were used to find out the possible synchronization in the gonad and light organ enlargement in both sexes. A significant positive correlation was observed between GSI and PLW in males but not in females; it can be suggested that gonad and light organ development correlate only in males during the breeding seasons irrespective of the length of the fish, whereas, the light organ remained the same size in all sexually mature females irrespective of the length of the fish and breeding seasons. The result suggested the possible role of bioluminescence in mate recognition in this silverbelly species as the same was reported for other species of silverbellies. It can be explained in terms of sexual selection imposed by reproductive success.

Photopectoralis bindus, gonadosomatic index, percentage light organ weight, symbiotic bioluminescence, leiognathidae