PENETRATION BY FIELD VOLE SPERMATOZOA OF MOUSE AND HAMSTER ZONAE-PELLUCIDAE WITHOUT ACROSOME REACTION

Spermatozoa of the field vole (Microtus montebelli) that bound to the zona pellucida of field vole oocytes underwent the acrosome reaction b efore passing through it. In contrast, vole spermatozoa that bound to the zonae of mouse and hamster oocytes penetrated the zonae without an y sign of the acrosome reaction. The presence or absence of proteinase /hyaluronidase inhibitors in the medium did not make any difference to zona penetration by acrosome-intact vole spermatozoa. These observati ons suggest that held vole spermatozoa can cross mouse and hamster zon ae mechanically without assistance from zona-hydrolysing enzymes.