Substructure of a cytoskeletal complex associated with the hamster sperm acrosome

Whole mount and thin section preparations of intact and selectively disrupted hamster spermatozoa revealed an organized array of cytoplasmic filaments associated with specific regions of the acrosome. The filaments were localized along the ventral surface of the spermatozoon and extended from its tip, distally to the anterior margin of the equatorial segment. Individual filaments were 11-13 nm in diameter and they were aligned parallel to one another to form a two-dimensional sheet oriented in the long axis of the spermatozoon. The filament complex adhered preferentially to the cytoplasmic surface of the outer acrosomal membrane rather than the plasma membrane. Examination of disrupted spermatozoa revealed that the distribution of this cytoskeletal assembly correlated with the distribution of a specific acrosomal matrix component. The possible role of this complex in the acrosome reaction or in the organization of acrosomal matrix domains is discussed.