A comparative study on histology of testes in Macaca nemestrina, M. fascicularis and M. fuscata

Abstract

For the purpose of examining hypotheses on the evolutionary mechanism of testis morphology, histological comparisons of spermatogenetic activities were carried out in three macaque species. Testis samples were obtained by biopsies from six adult crab-eating macaques, six adult pig-tailed macaques and five adult Japanese macaques. In the Japanese macaques, samples were taken twice in October (mating season) and April (non-mating season), respectively. Microscopic observations revealed that some seminiferous tubules of the pig-tailed macaques showed characteristic features of degeneration, which were not found in the other two species. The acrosomic system of the spermatids of crab-eating macaques was most developed, compared with the other two species. Seminiferous tubules showing active spermiogenesis were frequently found in crab-eating macaques and in pig-tailed macaques, compared with Japanese macaques in the non-mating season. The seminiferous epithelia in stages containing only one type of spermatids were frequently observed in pig-tailed macaques, compared with those in crab-eating macaques and in Japanese macaques in the mating season. These findings suggest that spermatogenic activity is most prominent in the crab-eating macaques and that the mechanism of sperm competition has affected testicular architecture of this species in the course of its evolution.