Sperm Transport in the Reproductive Tract of the Female Rabbit: I. The Rapid Transit Phase of Transport1,2

Rabbit spermatozoa were recovered from the upper ampulla and the fimbrial and ovarian surfaces of all females examined at 1 mm post coitum (p.c.). As many as 1,000 spermatozoa could be recovered, on occasion, from the upper ampulla, fimbria and ovary of individual animals within the first 15 mm p.c. After artificial intravaginal insemination, the incidence of rapid transport and distribution of sperm in the female tract were the same as in mated females. The rapid transit phase of sperm transport is an asymmetric phenomenon, occurring predominantly in the left side of the female tract of both mated and artificially inseminated does. Most spermatozoa were not motile after rapid transport and in more than 90% of these, the membranes overlying the acrosome were disrupted. After rapid transport, spermatozoa were located almost exlcusively in the uppermost regions of the oviduct. Most of the spermatozoa were cleared to the peritoneal cavity between 15 mm and 4 h p.c. and none appeared to reenter the lower levels of the female tract. The sustained migration of motile spermatozoa from the uterus into the oviduct was first detected at 90 mm p.c., when small populations of motile sperm were recovered from the lower isthmus of all animals examined. These observations show clearly that rapid passive transfer of rabbit spermatozoa to the upper oviduct and peritoneal cavity is a regular sequel to mating. Most sperm in this vanguard are dead and are cleared to the peritoneal cavity before ovulation and thus can have no direct role in fertilization.