Histological Analysis Of Horse,Donkey And Mule Testis Cell Types And Spermatogenesis

The mule is a highly adaptive, longevial domestic animal that results from the breeding of a horse(Equus caballus) to a donkey (Equus asinus). Due to the heterosis, it has some characteristics such as crude feed tolerance and higher disease resistance. The proverbial sterility in mules has been recognized for many centuries but the real nature of the cause of fertility in few of these hybrids is still not clear. This study was designed to develop a culture system for somatic fibroblast cells derived from the testis of horses, donkeys and mules. The karyotypes and G-band patterns of those cell lines were also examined. Histological comparison, cell types and situation of spermatogenesis of the testis in horses, donkeys and mules were performed by the technology of paraffin section with which it could provide some basis data for the reproductive regulation mechanism of the mules.The somatic cells were derived from the testis of those animals and standard method was used to prepare the chromosome spreading of those cell lines. The chromosome numbers in horse, donkey and mule were64(X,Y),62(X,Y) and63(X,Y) respectively. Smaller testis size and the total length of seminiferous tubules, lower seminiferous tubule volume density was observed in mules as compared to those in donkeys or horses. The total number of Sertoli cells per testis observed in mules was significantly higher than donkeys and/or horses. However, the total number of Ley dig cells in mules was significantly lower than in donkeys and/or horses. In addition, lower number of germ cells (spermatogonia and spermatocytes) present in mule seminiferous tubules compared to those in donkeys and/or horses.In summary, these results suggest that the chromosome pairing failure could be the main reason of sterility in mules.The mule testis has some characteristics that few blood vessels, a large number of white connective tissues, lower seminiferous tubule volume density, smaller diameter of seminiferous tubules, few mumber of leydig cells.