Laterality of spermatogenesis in pampas deer testicles (Ozotoceros bezoarticus)

There are previous reports of gonadal asymmetry in various mammal species. In pampas deer, the right testicle is significantly heavier and has greater volume than the left testicle. The aim of the study was to determine if there is laterality in the spermatogenic processes between both pampas deer testicles. The study was performed with 7 pampas deer males allocated at the Estacion de Cria de Fauna Autoctona (ECFA, Maldonado, Uruguay). They were anesthetised with a combination of ketamine, xylazine and atropine in darts flowed from a blowpipe during the breeding season (February), and fine needle aspiration (FNA) was performed in each testicle. The scrotal skin was rubbed with an antiseptic, and a sterile needle (23 G x 11/4´´, SAKIRA S.A.) connected to a syringe (5 mL) was inserted into the centre of the testicle. Half length of the needle was introduced into the parenchyma and the testicular content was aspirated through the syringe. Smears were prepared with the content collected from each testicle (approximately 20 µL) were dyed with McGrunwald-Giemsa and examined under 100 x 1.250 magnification in the optic microscope. A minimum of 200 (range: 200 to 265) spermatogenic cells as well as the total number of Sertoli cells present in the same images were counted, and the germ cells were classified as spermatogonia, spermatocyte, early spermatid, late spermatid and spermatozoas. The percentage of each stage of the germ line, the number of Sertoli cells, the relationship spermatozoa/spermatogonia and of spermatozoa/Sertoli cells in each testicle were compared with a paired t test. The right testicle tended to have more spermatogonias (3.4 ± 0.8 vs. 1.9 ± 0.4, right and left testicles respectively, P= 0.06) and had a greater percentage of early spermatids (25.6 ± 4.5 vs. 14.8 ± 5.2, right and left testicles respectively, P= 0.004) than the left testicle. On the other hand, the left testicle had a greater percentage of spermatozoas (5.3 ± 2.1 vs. 12.3 ± 4.8, right and left testicles respectively, P= 0.05), a greater spermatozoid/spermatogonia ratio (1.5 ± 0.5 and 8.2 ± 2.6, right and left testicles respectively, P= 0.02), and tended to have more spermatozoas/Sertoli cells (0.5 ± 0.2 and 1.0 ± 0.3, right and left testicles respectively, P= 0.07). While the right testicle had a greater incidence of cells from the earlier stages of spermatogenesis, the left one had the inverse relationship, with greater efficiency in spermatozoa production. Therefore, we concluded that although the right testicle is bigger and heavier, the spermatogenesis processes are more efficient in the left one.