Ultrastructure of ostrich (Struthio camelus) spermatozoa. II. Scanning electron microscopy.

The three-dimensional structure and size of ostrich sperm is unknown. In this study, the morphology and dimensions of ostrich sperm were determined by scanning electron microscopy of semen samples obtained from sexually mature males during the breeding season. The results indicate that sperm cells of the ostrich are of the sauropsid type characteristic of non-passerine birds and, in general appearance, resemble those of the chicken, turkey, guinea fowl, budgerigar and tinamou. They differ from tinamou sperm, however, in that they do not show a small bump at the tip of the acrosome. Ostrich sperm are shorter (69.6 microns total length) than those of the chicken, turkey and guinea fowl, but longer than those of the budgerigar. A lack of information makes it impossible to compare the dimensions of ostrich sperm with those of other ratites such as the rhea. In ostrich and guinea fowl, the sperm head is proportionately longer than that of the chicken, turkey and budgerigar as determined by tail to head ratios. Two distinct groups of ostriches could be distinguished on the basis of differences in the length of various sperm cell components. This may reflect persistent genetic (subspecies) variations in the domestic ostrich population.