Daily spermatozoal production, epididymal spermatozoal reserves and transit time of spermatozoa through the epididymis of the rhesus monkey.
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One testis and epididymis from each of 8 sexually rested, rhesus monkeys >6 yr old was removed during fall (the natural breeding season) to establish the productivity of the testis and the spermatozoal storage capacity of the epididymis. The efficiency of spermatozoal production was quite uniform and averaged 23 1 X 10 6 sperm per gram of testicular parenchyma per day, although testicular parenchymal weight ranged from 15 to 32 g. Daily spermatozoal production averaged 547 69 X 10 6 sperm per testis. Thus, the typical rhesus monkey produces about 1.1 X 10 9 sperm daily during the breeding season. The caput, corpus and cauda epididymidis in these sexually rested monkeys contained 0.6 0.1, 2.1 0.3 and 2.9 0.3 X 10 9 sperm and an additional 1.0 0.1 X 10 9 sperm were found in the proximal 49-70 mm of ductus deferens. The mean transit times of sperm through the epididymal segments were estimated as 1.1, 3.8 and 5.6 days for the caput, corpus and cauda, respectively. Based on comparisons with data for sexually rested males of seven other species, the transit time of sperm through the caput and corpus epididymidis is quite uniform at 2.0 to 5.5 days, despite a 265 fold difference in epididymal spermatozoal reserves. Thus, the time required for maturation of sperm within the epididymis is less than 5 days in several mammals including the rhesus monkey.