Sperm cells 'extremely efficient at swimming against current'

Researchers have said that sperm cells are extremely efficient at swimming against the current.

The discovery by researchers at MIT and Cambridge University may help us understand how some sperm travel such long distances, through difficult terrain, to reach and fertilize an egg.

Of the hundreds of millions of sperm cells that begin the journey up the oviducts, only a few hardy travelers 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.

In a bid to understand what the cells are capable of, the researchers instead built a series of artificial microchannels of different sizes and shapes, into which they inserted the sperm. They were then able to modify the flow of fluid through the tubes, to investigate how the cells responded to different current speeds.

They discovered that at certain flow speeds, the sperm cells were able to swim very efficiently upstream. "We found that if you create the right flow velocities, you can observe them swimming upstream for several minutes," Jorn Dunkel, an assistant professor of mathematics at MIT, and a member of the research team, said. "The mechanism is very robust."

The discovery is set to be published in the journal eLife.