Formation of the acrosome and basal body during spermiogenesis in a marine snail, Nerita picea (Mollusca: Archaeogastropoda)

摘要: In Nerita picea the proacrosomal granule is formed basally in early spermatid from one large cisterna of Golgi body, with which other Golgi-derived vesicles fuse. After has attached to plasma membrane and invaginated form a cup shape, endoplasmic reticulum inserts into open end deposits granular secretion on inner surface. Subsequently, proacrosome migrates along apex nucleus, but body remains basal, as occurs archaeogastropods also many polychaete annelids. However, final shape structure acrosome similar that mesogastropods. The annulus attaches distal centriole spermiogenesis. production flagellum by not only expands posteriorly moves centriolar complex causing an invagination where it bound annulus. During migration, secretes dense tube around flagellum, mitochondria fuse two spheres at base nucleus. nuclear plug closes off intranuclear canal until this stage rapidly reorganizes itself tubes material inside canal. centrioles continue flagellar production, break away annulus, move deep they together basal sperm. maturing spermatid, single sheath spirals flagellum. does migrate anterior midpiece, unusual for filiform Spermiogenesis features common both mesogastropods some unique features. These observations lend credence idea Neritidae are transitional group between Archaeogastropoda Mesogastropoda.