The Fine Structure of Spermiogenesis and the Mature Spermatozoon of Brachidontes variabilis (Bivalvia) PDF

Keywords

sperm, nucleus, Bivalvia

Abstract

The mature sperm of Brachidontes variabilis is of the primitive type, with a head, a midpiece, and a tail. The head comprises an inverted Y-shaped acrosome which has an anterior electron-dense region and a posterior electron lucent one. The sub acrosomal space is filled with flocculent material, but with no acrosomal rod. The nucleus is barrel-shaped with a posterior fossa. The midpiece consists of five mitochondria which surround the proximal and distal centrioles. Early spermatids have large central nuclei, and a number of scattered proacrosomal granules. In mid-spermatids, these granules coalesce into a large basal granule which migrates apically where it invaginates at its adnuclear surface and becomes an inverted Y-shaped vesicle. Nuclear condensation is of the granular pattern