Whatever the level of attraction a woman feels for a man, the same may not always be the case for her eggs.
That’s according to a new study that looked into the chemicals used by a female egg to attract male 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,’ said John Fitzpatrick, an associate professor at Stockholm University, which partnered with the Manchester University NHS Foundation Trust (MFT) for the study.
The scientists specifically looked at follicular fluid, which surrounds the eggs and contains the chemicals that attract sperm. They wanted to see if the fluids from different women attracted certain sperm more than others.
And, to put it bluntly, it does.
‘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,’ said Professor Fitzpatrick.
‘This shows that interactions between human eggs and sperm depend on the specific identity of the women and men involved.’
What’s more, it seems that even if a woman has chosen a partner to mate with, it’s not a given her egg and his sperm will attract each other.
The research team obtained anonymous egg and sperm samples from couples undergoing IVF at St Mary’s Hospital in Manchester.
According to Professor Fitzpatrick, sperm have only one job — to fertilise the eggs. So they won’t be choosy about which egg they fertilise. However it seems human eggs have evolved to benefit by picking high quality or genetically compatible sperm.
‘The idea that eggs are choosing sperm is really novel in human fertility’ said Professor Daniel Brison, the scientific director of the Department of Reproductive Medicine at Saint Mary’s.
A technician injecting human sperm into a human egg cell using a technique known as intracytoplasmic sperm injection (ICSI). (Science Photo Library (Photographer)
‘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.’
Credit: Metro UK