Abstract
In the rabbit, daily sperm production by the testes was estimated by determining the total number of spermatozoa and late spermatids contained in a testicular suspension, and the length of the spermatogenic cycle was estimated by an autoradiographic technique. In 20 bucks, 9 to 14 months old (mean weight 3.9 kg), which had spent 6.9 [plus or minus] 1.8 weeks in a constant photoperiod of 14 hr. light daily, the mean sperm production was 147.4 x 106/day and 1 g of their testicular tissue yielded 26.5 x 106 sperm/day. In another group of 13 bucks, 15 to 16 months old, which had spent 26.3 [plus or minus] 1.7 weeks under similar lighting conditions, mean sperm production was 115.8 x 106/day and 1 g of testis yielded 21.4 x 106 sperm/day. The difference between the 2 groups of animals is highly significant and it is postulated that a constant photoperiod is deleterious for sperm production. In rabbits collected from twice a week the daily sperm output was consistently lower than the testicular sperm production, indicating that slightly more than 50% of the spermatozoa produced are resorbed.