Seasonal variations in daily sperm production rate of rhesus and bonnet monkeys

Daily sperm production (DSP) rate was estimated in adult male rhesus and bonnet monkeys to evaluate seasonal changes in the gametogenic activity of the testes. Three monkeys of each species were castrated during breeding and non-breeding seasons and DSP rate was estimated by enumerating the homogenization-resistant spermatid nuclei of steps 13 and 14. Results indicated a significant reduction in the DSP rate per testis during the non-breeding season in two species, along with a marked decline in the testis weight. However, the gametogenic capacity of seminiferous tubules did not appear to be markedly affected during non-breeding season, as the DSP rate per gram parenchyma of testis was only marginally reduced. The seasonal changes in DSP were much more pronounced in the rhesus than in the bonnet monkey. The feasibility of circanual rhythm in DSP of sub-human primates to form a baseline for the study of reproductive function in male is discussed.