The ultrastructure of mink (Mustela vison) spermatozoa

Abstract

The subcellular structure of epididymal spermatozoa obtained from standard dark mink was studied. Conventionally prepared thin sections were observed under a transmission electron microscope. The mink spermatozoan head showed six swellings on the dorsoventral aspects: two connected hump-like swellings at the anterior border of the equatorial segment of the acrosome, and one at the post acrosomal sheath on each side. These swellings are a species-specific structural feature which might be necessary for recognition of the ovum or attachment to it in fertilization. The neck appeared to show a dorsoventrally continuous but laterally separated capitulum which was followed by two major and five minor columns, forming at first a striated ring and then joining with the dense fibers of the axial fiber bundle. The dense fibers numbered 9, 1,5, and 6 were larger than the rest. In the axonemal complex, subfiber A was larger than the central fiber, while subfiber B was the smallest. The middle piece was of medium length when compared with other mammalian spermatozoa. The shape of the annulus was triangular in longitudinal sections. The occurrence of swellings anterior and posterior to the equatorial segment of the head and the arrangement of the connecting piece, the modified capitulum, and the grouping of the striated columns are some of the important features of mink spermatozoa.