Demonstration that the removal of sialic acid from the surface of chicken spermatozoa impedes their transvaginal migration.

Staining of ejaculated chicken spermatozoa with lectin from FITC-conjugated Limulus polyphemus indicated a uniform distribution of terminal sialic acid residues on surface-associated glycoproteins throughout all regions of the spermatozoa. Treatment of spermatozoa with neuraminidase resulted in complete disappearance of this lectin affinity without any visible change in the viability of spermatozoa, as indicated by assessment in vitro of their motility, ATP content and ability to exclude eosin. Neuraminidase-treated spermatozoa were also severely limited in their ability to populate the uterovaginal sperm storage tubules after intravaginal insemination, although they were able to perform this function as well as untreated control spermatozoa after insemination directly into the uterovaginal region. These results demonstrate the presence of a mechanism that recognises sperm surface characteristics which inhibit transport of spermatozoa through the vagina of the chicken hen, but not the entry of spermatozoa into the sperm storage tubules. We hypothesize that cleavage of sperm surface sialic acid residues may increase antigenicity of spermatozoa in the vagina, resulting in their destruction by an immunologically-based sperm-selection mechanism.