Scientists reveal how females store sperm for decades

Scientists have discovered that all sorts of females – from birds to reptiles to insects – have a nifty trick to prolong the lifespan of sperm, letting them store it for weeks, months or even years on end.

They found that females do this by lowering the metabolic rate of sperm, so it can survive in their bodies almost indefinitely.

In one extreme example, biologists have shown that queen ants fertilise their eggs with sperm they've stored for up to 30 years. Normally, once it's outside the male's body, it doesn't survive for long.

The findings could explain why, in reproductive medicine, sperm samples aren't necessarily the best way to predict if someone can father children or not.

'Infertility tests on sperm are notoriously unreliable, and this could be one reason why,' says Dr Klaus Reinhardt from the University of Sheffield, who led the study, published in Proceedings of the Royal Society B.

It seems that females lower sperm's metabolic rate and stop sperm generating excessive amounts of highly damaging, reactive oxygen molecules – called free radicals. Having a slower metabolism in turn means sperm age much more slowly than usual.

At the moment, Reinhardt and his colleagues have no idea how females manage this.

'All cells produce these molecules, but sperm tend to produce more, probably because they have such fast metabolisms. What's more, reactive oxygen molecules are thought to accelerate aging in all cells. So it follows that getting rid of free radicals might extend the lifespan of sperm,' says Reinhardt.

Continued:  http://planetearth.nerc.ac.uk/news/story.aspx?id=1144