Sex rivals fuel 'chemical warfare' in flies

9 April 2009

When faced with sexual competitors male fruit flies transfer more chemicals to females in an attempt to change their sexual behaviour and physiology, research by an international team led by Oxford University scientists suggests.

The finding could help in the management of pests: making it possible to breed more sexually successful males for use in control programmes aimed at stopping female pests from reproducing.

The results of the study are published this week online in the journal Current Biology.

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.

'What we have found is that the use of seminal chemicals by competing male fruit flies can be very complex,' said Dr Stuart Wigby of Oxford University's Edward Grey Institute in the Department of Zoology, co-lead author on the paper with Dr Laura Sirot of Cornell University. '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.'

In species such as fruit flies the proteins are known to evolve rapidly which could be a consequence of males evolving new combinations to monopolise females and edge out other males, and females responding by evolving countermeasures to sidestep these chemical controls.

'Our findings could prove important for controlling the insect pests that damage crops or carry diseases,' said Dr Wigby. '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.'

For more information contact Dr Stuart Wigby on +44 (0)1865 271161 or email stuart.wigby@zoo.ox.ac.uk

Alternatively contact the University of Oxford Press Office on +44 (0)1865 283877 or email press.office@admin.ox.ac.uk