Sex war is fly vs fly

Maybe it’s simple mammalian prejudice but most of us don’t stop to consider flies having sex, let alone having sperm.

But of course they do, and Oxford’s Stuart Wigby has found that a study of the chemicals male flies release along with their sperm could be important in tackling insect pests as well as giving us a fresh insight into sexual competition in many species, including our own.

A team led by Stuart report in Current Biology that when faced with sexual competitors male fruit flies transfer more chemicals to females in an attempt to change their sexual behaviour and physiology.

This sexual ‘chemical warfare’ between males revolves around seminal fluid proteins that are transferred in the fly’s seminal fluid alongside sperm. In insects these proteins can cause females to store sperm, lay eggs faster, and can act as anti-aphrodisiacs, making females less sexually receptive.

The team showed that male fruit flies [Drosophila melanogaster] use these proteins strategically; increasing the amount transferred when other males are present. They also found that males that are able to transfer more of these proteins have more offspring – making it likely that the amounts delivered determine the reproductive success of males.

Stuart told us: ‘As similar proteins are known in other species including arthropods and mammals – including humans – our results give a tantalising insight into how the different sexual strategies of males and females have evolved.’

‘Our findings could prove important for controlling the insect pests that damage crops or carry diseases. At the moment the sterile males used to control populations of pest insects are often not very successful at out-competing male rivals in the mating game; this research suggests how future control programs might selectively breed sexually competitive males.’

Dr Stuart Wigby is based at Oxford’s Department of Zoology