Promiscuous fruit flies go under the microscope

Female fruit flies sleep around. Nobody knows exactly why, but Nina Wedell of Leeds University’s school of biology aims to find out.

Conventional wisdom on animal mating strategies said that females sought male partners with healthy genes to pass on to offspring, but this theory is now discredited, as it does not explain all variations of behaviour.

Instead it has been found that females often mate with numerous partners and screen sperm so that only the most healthy is used. What is a mystery, however, is which criteria are used to sort out the less desirable sperm.

The females of some species, such as crickets, screen for the relatedness of sperm, rejecting that from near relatives (see Reporter 475). Dr Wedell believes that female fruit flies may block sperm that contains so-called ‘selfish genes’ which may skew the 50/50 male/female ratio of future generations.

Selfish genes – many of which are present in the genome of all animals – are genes which use biological organisms as ‘vehicles’ for making more copies of themselves even if they reduce the transmission of other genes they share a cell or organism with.

Dr Wedell said: “We want to examine the pattern of female fruit fly mating and understand what they are trying to achieve. If the female risks encounters with selfish genetic elements will she mate more?

“If we can determine why females mate as frequently as they do it could prove useful to understanding a host of issues, including how we can conserve diversity. We are using the fruit fly because its genetics and its life cycle are well known – we know just about every gene in its body so it is possible to ask a lot of specific questions about it.”