Sperm against the stream

Research may explain how sperm travel long distances, through difficult terrain, to reach an egg. Our findings highlight the very subtle interplay between the geometry of the sperm cells and their response to fluid flow near the chamber walls - Raymond Goldstein Like salmon travelling upstream to spawn, sperm cells are extremely efficient at swimming against the current. In a new study, researchers from the University of Cambridge and MIT have identified the physical mechanisms which may allow sperm to navigate inside the human body and stay on course through a variety of environments. The research may help us to understand how some sperm travel such long distances, through difficult terrain, to reach and fertilise an egg. The results are published today in the journal eLife . Of the hundreds of millions of sperm cells that begin the journey up the Fallopian tube, only a few hardy travellers will ever reach their destination. Not only do the cells have to swim in the right direction over distances that are around 1,000 times their own length, but they are exposed to different chemicals and currents along the way.