ULTRASTRUCTURE OF THE SPERMATOZOA OF THE PACIFIC OYSTER CRASSOSTREA-GIGAS (MOLLUSCA, BIVALVIA, OSTREIDAE)

The basic ultrastructural morphology of Crassostrea gigas sperm is cha racteristic of and consistent with that observed in other ostreid spec ies, including C. virginica, C. angulata and Ostrea edulis, as well as Saccostrea commercialis. However, each has unique features. A striate d centriolar rootlet and a sidefin in the flagellum are reported for t he first time in C. gigas. The observations reported here extend our d ata base on sperm morphology in ostreid species. The results of the pr esent study support the suggestions that sperm ultrastructure is of ta xonomic importance and may be a phylogenic criterion in the family Ost reidae.