Morphology and motility of spermatozoa from different regions of the epididymal duct in the domestic cat.

Spermatozoa undergo important maturational changes as they pass through the epididymal duct. Some domestic cats and many species of wild felids have high proportions of abnormal spermatozoa in their ejaculates. The epididymis has been shown to be able to remove certain abnormal sperm forms in some species while other sperm abnormalities originate in the epididymis. So far, it has not been shown how the epididymis affects sperm morphology in the domestic cat. Therefore, motility and sperm morphology were studied in spermatozoa from the efferent ducts and from the 6 regions of the epididymal duct. There were significant decreases in the proportions of spermatozoa with abnormalities of the sperm head, acrosomal defects, acrosomal abnormalities and in the proportion of midpiece abnormalities. In contrast, there was a small but significant increase in the proportion of spermatozoa with abnormalities of the tail. Spermatozoa acquired the capacity for motility in Region 4, where the cytoplasmic droplet also moved from a proximal to a distal position, indicating that important maturational changes take place in this region. The results of this study demonstrate that the proportions of sperm abnormalities originating in the testes decrease during epididymal transport, while some sperm tail abnormalities may actually originate in the epididymis.