Inability of round acrosomeless human spermatozoa to penetrate zona-free hamster ova.

The spermatozoa from five healthy men of proved fertility and five infertile men with a single abnormal semen parameter associated with high proportion of round acrosomeless heads were evaluated for their ability to bind to and to penetrate zona-free hamster ova. Sperm from five men of proved fertility penetrated a high proportion of the eggs (16-80%) while sperm from men of the infertile group failed to bind and to penetrate any of the ova. Round acrosomeless sperm do not have the ability to bind to or to fuse with the vitellus of zona-free hamster eggs.