Smells like?

As some of you know I have spent the last 9 months working with Steve Chenoweth at The University of Queensland where we use the model species Drosophila serrata. In this species (and other Drosophila) males court females using a blend of cuticular hyrocarbons (CHCs) that are produced in the oenocytes of both sexes (see pic above), located on the inner surface of the animal’s abdominal cuticle. These CHCs are known to explain around ¼ of male mating success in D.serrata, and are the subject of a lot of work produced by both Mark Blow’s and Steve’s Lab.

With this in mind I wanted to draw your attention to a recent paper in Nature on the important role of the CHC’s produced by another species of Drosophila, D.melanogaster, not only intraspecfic mating interactions, but also species identity and interspecfic matings. In the paper by Billeter et al. (sorry, not open access) they explain how they knocked out the production of the oenocytes of adult male and female D.melanogaster and found some interesting results. Firstly flies missing the oenocytes (oe-) became a hyper-sexual stimulas to other wild caught males. Oe- males and females were courted and mated far more than their wild caught counterparts. By applying different pheromone compounds, singularly, to the oe- individuals they found a slowing in male mating attempts (ie the female pheromones actually put the males off). Another interesting find was that female oe- were actually courted and mated with males from another species (D.simulans), and again by applying one pheromone compound restored the species barrier.

So a few CHC’s in D.melanogaster have been shown to control male-male mating interactions, influence male courting rates and act as a species barrier to other Drosophila males. Think about that next time you try a unisex eau de toilette.

Abstract:

Social interactions depend on individuals recognizing each other, and in this context many organisms use chemical signals to indicate species and sex1. Cuticular hydrocarbon signals are used by insects, including Drosophila melanogaster, to distinguish conspecific indi- viduals from others1–3. These chemicals also contribute to intraspe- cific courtship and mating interactions1–3. However, the possibility that sex and species identification are linked by common chemical signalling mechanisms has not been formally tested. Here we pro- vide direct evidence that a single compound is used to communicate female identity among D. melanogaster, and to define a reproductive isolation barrier between D. melanogaster and sibling species. A transgenic manipulation eliminated cuticular hydrocarbons by ablating the oenocytes, specialized cells required for the expression of these chemical signals. The resulting oenocyte-less (oe2) females elicited the normal repertoire of courtship behaviours from males, but were actually preferred over wild-type females by courting males. In addition, wild-type males attempted to copulate with oe2 males. Thus, flies lacking hydrocarbons are a sexual hypersti- mulus. Treatment of virgin females with the aversive male phero- mone cis-vaccenyl acetate (cVA) significantly delayed mating of oe2 females compared to wild-type females. This difference was elimi- nated when oe2 females were treated with a blend of cVA and the female aphrodisiac (7Z,11Z)-heptacosadiene (7,11-HD), showing that female aphrodisiac compounds can attenuate the effects of male aversive pheromones. 7,11-HD also was shown to have a crucial role in heterospecific encounters. Specifically, the species barrier was lost because males of other Drosophila species courted oe2 D. melano- gaster females, and D. simulans males consistently mated with them. Treatment of oe2 females with 7,11-HD restored the species barrier, showing that a single compound can confer species identity. These results identify a common mechanism for sexual and species recog- nition regulated by cuticular hydrocarbons.