Fruity aromas: An aphrodisiac for flies

An unexpected olfactory perception mechanism in male vinegar flies (/Drosophila melanogaster/) leading to their sexual stimulation has been identified and analyzed by CNRS researchers from the Centre des Sciences du Goût et de l'Alimentation (CNRS/Université de Bourgogne/INRA) in Dijon, in collaboration with a Swiss laboratory at Lausanne University and a British team in Cambridge. The scientists have shown that phenylacetic acid, a molecule associated with food-derived odors (present in flowers, fruit, honey, etc.) appends itself to a specific olfactory molecular receptor (IR84a) situated on male flies' antennae. Detection of this particular scent by this specific receptor triggers the significant activation of some thirty specific neurons, which sets off a defined neuronal circuit resultingin increased sexual arousal of the male fly.

Described for the first time, the olfactory molecular receptor IR84a maintains the sensorial neurons permanently active, even without odor, so as to keep the male flies ready to attract a potential partner. In this way, the more "perfumed" (with phenylacetic acid) the partner, the more attractive it will be, thereby greatly increasing the insect's sexual arousal. This is proved by genetically deleting theexpression of the receptor, which considerably reduces the sexual activity of the male flies (both with and without "perfume").

This olfactory perception mechanism is especially important in "fruit fly" species in the wider sense: the advantage of mating near food sources is obvious for the offspring. Additional work could help to discover similar mechanisms in other animal species.