Morphology of the spermatozoon of the limpet Fissurella crassa Lamarck, 1822 (Mollusca: Vetigastropoda)

Abstract

Summary Fissurella crassa is a keyhole limpet, which inhabits the middle rocky intertidal zone of the southwest coast of South America. The present study details the ultrastructure of the spermatozoon of this species. These cells are of the aquasperm type, typical of species that release free gametes into seawater. The conical head of the spermatozoon contains a truncated conical, elongated nucleus with a subconical acrosome with a rounded anterior tip, and a deep subacrosomic space. The midpiece of the spermatozoon is typically formed of six mitochondria arranged in a ring around the proximal and distal centrioles, from which emerges the 9 + 2 axoneme of the flagellum. The spermatic morphology is characteristic by the shape and size of the nucleus and acrosome, showing two differentiated zones and a deep subacrosomic space, which are valid taxonomic criteria to distinguish F. crassafrom other fissurellid species.