Gamete ultrastructure in two species of the genus Upeneus (Mullidae) from the South China Sea

Ultrastructure of envelopes of ovulated oocytes and spermatozoon ultrastructure are described in two closely related species of the family Mullidae, Upeneus tragula and U. cf. margarethae. Oocyte envelope is represented by the thin zona radiata and weakly expressed chorion. The spermatozoon is characterized by the presence of elongated head with a pointed bend in its apical part and nuclear fossa reaching approximately 90% of the head length. The centriolar complex and basal part of the flagellum are located inside of the nuclear fossa.