CONICET | Buscador de Institutos y Recursos Humanos

Sperm ultrastructure in two species of the marine snail family Olividae is examined. Euspermatozoa of both species are composed of a conical, membrane-bound acrosomal vesicle; an axial rod and a basal plate similar in both species; a solid and highly electron-dense nucleus; an elongate midpiece consisting of the axoneme sheathed by helical mitochondrial elements; an elongate glycogen piece; a double electron-dense ring at the junction of the midpiece and glycogen piece; and a free tail region. The slight narrowing in the acrosomal vesicle invagination is situated in different levels between O. deshayesiana and O. carcellesi. This morphology could be considered as specific character. The length of the nucleus in Olivancillaria carcellesi and Olivancillaria deshayesiana is shorter than that of other neogastropods, and could be diagnostic at family level.