A detailed ultrastructural study of the head membranes of ejaculated bovine sperm

Abstract

The distribution of membranes in the ejaculated bovine spermatozoon has been investigated after several types of fixation. The apical body has no connection with the nuclear envelope and has a definite structure. The nuclear membranes differ in their appearance in various parts of the sperm head. Nuclear pores are present only in the skirt of nuclear membrane which projects below the nucleus. The "basal knobs" of nuclear material fill part of this skirt. There is little or no space for "subacrosomal material" or "cytoplasm" under the anterior part of the acrosome. However, in the equatorial segment amorphous material coats the whole of the inner acrosomal membrane and half the length of the membrane facing the plasmalemma. This amorphous material is continuous with the postnuclear cap, which consists of a sheet of material of complex structure. The possible functions of the various constituents are briefly discussed. © 1971 Academic Press, Inc.