Spermiogenesis in Polyplacophora, with special reference to acrosome formation (Mollusca)

摘要: The present study examines spermiogenesis, and in particular the formation of acrosome, ten species chitons belonging to four families. This emphasizes acrosome but brings light several other structures that have received little or no mention previous studies. process spermiogenesis is essentially similar each species, although Chaetopleura exhibits some significant differences. In early Golgi body secretes numerous small pro-acrosomal vesicles gradually migrate into apical cytoplasm. chromatin condenses from granules fibres which become twisted within nucleus. A bundle projects main nuclear mass anterior filament; this coincides with appearance a developing manchette microtubules around nucleus originates two centrioles. Radiating distal centriole centriolar satellite complex, attached plasma membrane by annulus. produces flagellum posteriorly it exits eccentrically through ring folded houses Extending annulus on one side flagellum, all dense fibrous has not been previously reported. proximal lies perpendicular end fibro-granular material. Pro-acrosomal anteriorly cytoplasm move filament expanding Eventually these way tip sperm, where they fuse form acrosome. mature sperm bullet-shaped long contains occasional lacunae. mitochondria vary both number position different species. Both centrioles are housed posterior indentation nucleus, membranes modified. elongate tapers filamentous end-piece roughly corresponds may be important locomotion for hydrodynamic reasons. An stained positively acid phosphatase three were tested.