| Mule, the hybrid of horse and donkey, is sterile. Quite rarely, there are some female mules are fertile. However, there is not any fertile male mule have been reported till now. In this study, we analyzed biopsies of testis from four male mules and compared them with the normal male horse and donkey. Fibroblasts were isolated from the testis and chromosome specimens were prepared by the fibroblasts. Besides, HE staining and immuno-florescent histochemistry were used to analyze and compare the difference between the testes. These studies provide some cellular and tissue evidence for the sterility of mule and pave the way for researching the mechanisms of mule’s reproductive regulation.The results showed that male mule has a hybrid karyotype of2n=63(XY), while the kayotype of male horse and donkey are2n=64(XY),2n=62(XY), respectively. Compared to the male horse and donkey, the inter-seminiferus tubule distance, inner-seminiferus tubule cavity in mule testes are bigger, while the cell number in mule’s seminiferus tubule is lower. The average numbers of spermatogonia and spermatocyte per seminiferus tubule of the four mules are0.0,16.5,13.4and24.2; while in donkey and horse, the numbers are50.6and43.5, respectively. The average numbers of SCP3-positive cells in each seminiferus tubule of mules are0.0,2.7,0.6and16.3. While in the seminiferus tubules of donkey and horse, SCP3-positive cell numbers are17.5and12.5, respectively. There is not any spermatozoon was found in the seminiferus tubules of all the four mules. Contrarily, seminiferus tubule of horse contains47.4spermatozoa and donkey has49.7in average. Both the mules and the compared horse and donkey have normal Sertoli cells in their testis.In summary, compared with male donkey and horse, the inter-seminiferus tubule distance and inner-seminiferus tubule cavity of mules are bigger. The number of spermatogonia, spermatocyte and SCP3-positive cells in the seminiferus tubules are fewer. Especially, there was not spermatozoon found in the testes of mules. We hypothesize that spermatogenesis blocking in mules should result from the retardation of meiosis. |
