CANINE EPIDIDYMAL SPERMATOZOA: CHARACTERISTICS, COLLECTION AND CRYOPRESERVATION.

Epididymal spermatozoa represent the only source of genetic material when the male dies unexpectedly or undergoes orchiectomy for medical reasons. Yet, in individuals of high genetic or emotional value that cannot mate or ejaculate semen, the collection of spermatozoa from in situ epididymides might be an option to obtain progeny. The aims of the studies presented here were to describe the characteristics of spermatozoa collected from the different regions of the epididymis (caput, corpus, and cauda) and to investigate the feasibility of percutaneous epididymal sperm aspiration (PESA) in dogs. Furthermore, the preservation of DNA integrity in canine epididymal frozen spermatozoa and the potential protective effect of the antioxidant melatonin on post-thaw sperm quality were evaluated. Overall results showed that canine epididymal spermatozoa undergo several modifications in the epididymis, leading to mature cells which are stored in the epididymal cauda. From this site, spermatozoa can be retrieved by PESA and the quality of the sperm population is similar to that of spermatozoa collected in vitro, although a wide variation amongst animals was observed. The cryopreservation of epididymal spermatozoa showed that the DNA integrity is well preserved, but a protective effect of melatonin on post-thaw sperm quality has not been demonstrated. The DNA stability after thawing is particularly relevant for epididymal spermatozoa which potential use in assisted reproductive techniques is mainly after storage. However, other sperm characteristics as motility and acrosomal integrity are compromised by freezing and further investigations should be focused on their preservation.