TIME AND PROCESS OF SPERM PENETRATION INTO HAMSTER OVA IN VIVO AND IN VITRO

Abstract

Female golden hamsters were mated at various times before or after ovulation, and the time of sperm penetration into the ova was examined. When the females were mated several hours prior to ovulation, penetration of spermatozoa into the ova started about 3 hr. after the commencement of ovulation or about 1. 5 hr. after the 1st ovum passed into the Fallopian tube; virtually all the ova were penetrated in the next 4 hr. In the females mated during or several hours after ovulation, sperm penetration occurred between 3 and 6 hr. after coitus. The experiments in which spermatozoa were deposited artificially in the uteri of females shortly after ovulation, demonstrated that the spermatozoa recovered from the uterus of other females penetrated ova significantly faster than epidi-dymal spermatozoa. The uterine spermatozoa deposited about the ova in vitro were also able to penetrate the ova more quickly than epididymal spermatozoa. The whole process of sperm penetration through the zona pellucida was observed on one occasion. This particular observation showed that: the acrosome (at least, the outer acrosome membrane) of the fertilizing spermatozoon was absent before the spermatozoon started to penetrate the zona pellucida; the direction of the passage of the spermatozoon was not vertical, but at an angle to the surface of the zona pellucida; the time required for the sperm head to traverse the zona pellucida and the perivitelline space was 3 to 4 min. and 1 to 2 sec. respectively; the head of the spermatozoon lay flat on the vitelline surface and sank into the vitellus without lively movements of the sperm flagellum.