Fertilizing ability of mouse sperm from different epididymal regions and after washing and centrifugation.

The ability of caput, corpus, and cauda epididymal and vasa deferentia mouse sperm to fertilize eggs in vitro was investigated. Cauda epididymal sperm fertilized 45 of 54 ova, whereas caput and corpus sperm fertilized a negligible number of ova, thus indicating their immaturity. Vasa deferentia sperm fertilized only 10 of 52 ova and their reduced fertility may be due to aging in vivo. No difference in preimplantation development of the resulting zygotes with respect to the sperm source was observed. Three centrifugations and resuspensions of cauda epididymal sperm in fresh medium did not affect their fertilizing ability. I conclude that fertilization in vitro can occur after removal of epididymal secretions.