Gonad structure and sexual pattern in two threadfin breams and possible function of the dorsal accessory duct

A dorsal accessory duct (DAD) structure was found on the dorsal side of a functional testis in all males of both Nemipterus virgatus and N. japonicus, and determined to be homologous to the ovary, based on structural, histological and cytological evidence. Secretions, in the DAD varied according to reproductive season and were particularly marked in N. virgatus. The sexual pattern of both species was functional gonochorism. The secretions of the DAD suggest some unknown function, possibly associated with spawning, which has evidently arisen de novo within a rudimentary ovary: this is the only example of its type reported among hermaphroditic fishes. © 2001 The Fisheries Society of the British Isles.link_to_subscribed_fulltex