Experiments with spermatozoa of prepubertal hamsters aged 35-48 days were performed in order to determine if the appearance of spermatozoa with fertilizing capacity in the cauda epididymis during puberty is related to changes in their morphology, motility and number. Epididymal spermatozoa of prepubertal animals were evaluated for number, motility and morphology and were injected into one uterine horn of a female, following induction of ovulation. A comparable number of sperm from mature animals (which served as control) was injected into the contralateral horn. Prior to 40 days fertilizing capacity was nil. It increased thereafter and reached control levels of 74% at 48 day age. Concomitantly there was an increase in the number of sperm per cauda epididymidis from less than l million to 55 million. Following removal of spermatozoa from the cauda the motility increased from 24% motile cells at the age of 39 days to 66% at the age of 48 days when most cells exhibited progressive motility.The percentage of cells having normal morphology increased from 18% at the age of 39 days to 50% at the age of 48 days. Developmental processes resulting in improvement of cell motility, morphology and number are correlated with attainment of fertilizing capacity. These processes seem to be gradual and occur between time of completion of spermatogenesis and time when capacity for fertilization is achieved.

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Male golden hamster sperm acquire complete fertilizing ability at about 48 days of age. In this study hamsters, 27-130 days of age were killed and their male reproductive tracts examined. Sperm were found in the caudae epididymides from 37 days onward. None of the sperm from animals younger than 41 days were capable of fertilizing ova when placed in the uteri of superovulated females. Using flow cytometry of acridine-orange-stained cells, the chromatin condensation in cauda epididymal sperm was investigated. It was seen that DNA from sperm from the younger animals (under 40 days of age) was less tightly bound to protamine than that obtained from mature animals. In summary, the earliest sperm produced by pubertal hamsters were immature with regard to chromatin condensation, morphology, motility, and ability to fertilize ova, and they developed mature characteristics in the period between 40-48 days of age.

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