Different Women’s Eggs Attract Different Men’s Sperm – And Not Necessarily Their Partners

Sperm and Egg Cell

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Human Eggs Prefer Some Men’s Sperm Over Others

Human eggs utilize chemical signals to draw in sperm. New research study from Stockholm University and Manchester University NHS Foundation Trust reveals that eggs utilize these chemical signals to “choose” sperm. Different ladies’s eggs draw in various males’s sperm — and not always their partners.

John Fitzpatrick

Dr John Fitzpatrick, Wallenberg Academy Fellow, Department of Zoology, Stockholm University. Credit: Magnus Bergström/Knut and Alice Wallenberg Foundation

Humans invest a great deal of energy and time picking their partner. A brand-new research study by scientists from Stockholm University and Manchester University NHS Foundation Trust (MFT) reveals that picking your partner continues even after sex — human eggs can “choose” sperm.

“Human eggs release chemicals called chemoattractants that attract sperm to unfertilized eggs. We wanted to know if eggs use these chemical signals to pick which sperm they attract,” stated John Fitzpatrick, an Associate Professor at Stockholm University.

The scientists analyzed how sperm react to follicular fluid, which surrounds eggs and includes sperm chemoattractants. The scientists wished to learn if follicular fluids from various women brought in sperm from some males more than others.

Microscopic mate option

“Follicular fluid from one female was better at attracting sperm from one male, while follicular fluid from another female was better at attracting sperm from a different male,” stated Professor Fitzpatrick.

Daniel R Brison

Professor Daniel R Brison, PhD, FRCPath Scientific Director, Department of Reproductive Medicine, Manchester University NHS Foundation Trust. Credit: Manchester University NHS Foundation Trust

“This shows that interactions between human eggs and sperm depend on the specific identity of the women and men involved.”

The egg does not constantly concur with the ladies’s option of partner. The scientists discovered that eggs did not constantly draw in more sperm from their partner compared to sperm from another male.

Is this egg or sperm option? Professor Fitzpatrick described that sperm have just one task — to fertilize eggs — so it doesn’t make good sense for them to be picky. Eggs on the other hand can benefit by choosing high quality or genetically suitable sperm.

“The idea that eggs are choosing sperm is really novel in human fertility,” stated Professor Daniel Brison, the Scientific Director of the Department of Reproductive Medicine at Saint Marys’ Hospital, which becomes part of MFT, and the senior author of this research study.

The University of Manchester Honorary Professor included: “Research on the way eggs and sperm interact will advance fertility treatments and may eventually help us understand some of the currently ‘unexplained’ causes of infertility in couples.”

“I’d like to thank every person who took part in this study and contributed to these findings, which may benefit couples struggling with infertility in future.”

The post “Chemical signals from eggs facilitate cryptic female choice in humans” is released in the clinical journal Proceedings of the Royal Society B.

Reference: 9 June 2020, Proceedings of the Royal Society B.
DOI: 10.1098/rspb.2020.0805

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