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

Daily sperm production (DSP) rate was estimated in adult male rhesus and bo nnet monkeys to evaluate seasonal changes in the gametogenic activity of th e testes. Three monkeys of each species were castrated during breeding and non-breeding seasons and DSP rate was estimated by enumerating the homogeni zation-resistant spermatid nuclei of steps 13 and 14. Results indicated a s ignificant reduction in the DSP rate per testis during the non-breeding sea son in two species, along with a marked decline in the testis weight. Howev er, the gametogenic capacity of seminiferous tubules did not appear to be m arkedly affected during non-breeding season, as the DSP rate per gram paren chyma of testis was only marginally reduced. The seasonal changes in DSP we re much more pronounced in the rhesus than in the bonnet monkey. The feasib ility of circanual rhythm in DSP of sub-human primates to form a baseline f or the study of reproductive function in male is discussed.