Ovules choose sperm that will fertilize them

Ovules choose sperm that will fertilize them

In nature, the bridal parades of some species are treasures of inventiveness that allow females to choose the male whose genetic heritage will give the best descent. How females make their choice is a well kept secret.

But for mammals, this ′′ female selection ′′ also takes place at a cellular level. Indeed, the ovules, through chemoattractive molecules, select the best sperm. This phenomenon has been described in mice or cetaceans but remains quite unrecognized in humans although it is already known that the molecules secreted by the ovum guide sperm to it.

A study published in Proceeding of the Royal Society B suggests that human ovules also make their choice among sperm that come to them through the same mechanism. And sometimes those who respond best to chemical molecules don’t necessarily belong to the woman’s loving partner.

The ovum attracts sperm

This experiment was carried out on couples who are being followed for in vitro fertilization. Scientists have recovered the fluid surrounding the ovum into the follicles and into which it spills its chemoattractive molecules, as well as participant sperm. Then they watched the behavior of sperm from several donors against different follicular fluids.

The results suggest that sperm respond differently to each follicle fluid. Ovules, thanks to the molecules they secret around them, therefore attract sperm belonging to a specific man.

′′ A given woman’s follicular fluid was better at attracting a given man’s cum, when another woman’s follicular fluid was better at attracting another man’s cum ", explains Professor Fitzpatrick of Stockholm University and first author of the study. But the man’s cum favorite by the ovum doesn’t necessarily belong to his fellow lover.

The structure of the sperm. This is the head that reacts to chemoattracting molecules secreted by the ovum.

The structure of the sperm. This is the head that reacts to chemoattracting molecules secreted by the ovum.

Chemistry over love

Scientists have tested sperm response to follicular fluid from a couple or two strangers. Conclusion, the sperm of a given man does not add up more around his partner’s follicular fluid. So love doesn’t result in better sperm affinity for the ovum.

And because of this, spermatozoids only have one goal: to swim to the ovum to fertilize it. So he has no interest in doing the difficult, according to Professor Fitzpatrick. On the other hand, the ovum has every reason to carefully choose the sperm that will fertilize it for its genetic characteristics or for its affinity for the chemoattractants it secrets.

Thus, the cause of fertility problems could not be, among others, too slow or small sperm or ovulation fault, but a lack of biochemical compatibility between the ovum and sperm.