Binding of morphologically abnormal sperm to mouse egg zonae pellucidae in vitro

The ability of morphologically abnormal mouse sperm to bind to the zona pellucida of the egg was examined with techniques of fertilization in vitro. After incubation with sperm, cumulus-free ova were scored by either phase microscopy or scanning electron microscopy for the number and type of sperm bound. The percentages of abnormal sperm bound to zonae were compared to the percentages of abnormal sperm in the inseminating suspension. In general, all abnormal classes (except broadly spatulate sperm) bound to zonae at a frequency significantly lower than their representation in the inseminating suspension. However, when the percentage of abnormal sperm was quite high, no significant difference existed between frequencies of abnormal sperm bound and in the inseminating solution. The percentage of abnormal sperm bound did not increase significantly over time. Scanning electron microscopy studies demonstrated that the association of abnormal sperm with the zona pellucida varied according to sperm morphology. Normal and some abnormal sperm bound at an angle perpendicular to the zona, while more grossly abnormal sperm bound to ova tangentially.