Male Genotype Influences Sperm Transport in Female Mice1

The number of sperm in the oviducts of female mice mated to either C57BL/6-+/+ (B6-+/+) or C57BL/6-tW32/+ (B6-tW32/+) males was determined for the first 3 h after ovulation. In females mated to B6-+/+ males, the mean number ± SEM of sperm in the isthmus decreased significantly, from 4400 ± 600 at 13 h post-hCG treatment to 2500 ± 700 at 15 h post-hCG (a total of 15 females were examined for each male genotype). In females mated to B6-tW32/+ males, the mean number of sperm in the isthmus was similar (about 2000 ± 500) at all times examined. Very few sperm were observed at the site of fertilization after mating to either type of male. A significant increase in mean number of sperm per female at the site of fertilization was observed between 13 and 15 h in both types, but the increase occurred earlier in females mated to B6-tW32/+ males, suggesting that sperm from B6-tW32/+ males arrive at the eggs sooner than do normal sperm. The results of this study demonstrate that the male genotype can be influential in sperm transport within the female.