Studies on the polymorphic spermatozoa of a marine snail. 2. Genesis of the eupyrene sperm

Abstract

AbstractSpermiogenesis of the eupyrene sperm in the snail, Fusitriton oregonensis, was studied with light and electron microscopes. Endoplasmic reticulum, which encircles the nucleus in each spermatid, appears to connect with the Golgi body and to interconnect between adjacent spermatids via cytoplasmic bridges. It is suggested that as the Golgi body migrates around the nucleus the endoplasmic reticulum may circulate with it. The alignment of the proacrosome with the nucleus is effected by a 180° rotation of the Golgi body, after which it separates and migrates posteriorly with the residual cytoplasm. Each sperm possesses a well‐developed intracellular digestive system as indicated by multivesicular bodies, residual bodies, and myeloid figures. Autophagy begins in the residual cytoplasm before it is released from the middle piece. Microtubules are found outside the nucleus and mitochondria during the final stages of spermiogenesis, when elongation is almost complete. These microtubules appear to be involved in the final shaping and twisting process, in which torsion is locked in the nucleus and the mitochondria spiral around the axoneme. The annulus attaches the distal centriole to the plasma membrane in the early spermatid and as flagellar production begins they move towards the implantation fossa at the base of the nucleus. There are two centrioles in the early spermatid, the distal centriole and procentriole. The small procentriole fuses with the distal centriole in the intranuclear canal to form the centriolar cap of the basal body. This cap is pushed through the end of the nuclear tube and is separated from the subacrosomal space by only the nuclear membranes.