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Young flies smell sweeter09.02.2012 - (idw) Westfaelische Wilhelms-Universität Münster
Young fruit flies are sexually more attractive for the other sex / publication in "Journal of Experimental Biology"
Old fruit flies are less sexually attractive than their younger counterparts. This is what an international team of researchers led by Prof. Scott Pletcher and Dr. Tsung-Han Kuo from the Baylor College of Medicine in Houston and Michigan University has discovered. The scientists demonstrate that changes in the flies' own body scents play a central role in their attractiveness. The German partners involved in the study, which has now been published in the Journal of Experimental Biology, are researchers from the Institute of Medical Physics and Biophysics at Münster University.
Like many other insects, fruit flies of the species Drosophila melanogaster use special hydrocarbon compounds expressed on the surface of their body for chemical communication. Some of these messengers are detected by others of the species by smell or by taste through contact receptors located on the legs and proboscis (mouth part). This is similar to the principle whereby humans taste food by means of receptors on the tongue. A particularly important role is played by sexual pheromones, which can influence the sex drive. The team of researchers has now demonstrated that the composition of hydrocarbons changes significantly as both male and female fruit flies grow older.
In order to test whether these changes influence behaviour, the scientists gave the flies a choice between two possible partners for mating. The result was that male fruit flies preferred to be closer to younger females and made more frequent displays of courtship, even in the dark where optical stimuli should play no role. In order to test whether the scent really was the deciding factor for this decision, the researchers offered the males the scents from old and young females, applying these scents to special odourless female flies. The result was the same: the scent from the young females was more attractive for the males. When females were tested with two males, the scientists observed a slightly modified behaviour. Although the female flies preferred being closer to younger partners, they only did so in the light. This is why the researchers suspect that both optical stimuli and scent play a role when the female selects a mate.
The chemical analyses took place at Münster University, at the Institute of Organic Chemistry and the Institute of Medical Physics and Biophysics. Using special mass spectrometric processes, the Münster scientists were able to identify and quantify many individual hydrocarbons sampled from the flies' body surface. Prof. Klaus Dreisewerd, a physicist, and Dr. Joanne Yew, a biologist and a visiting academic at the Institute of Medical Physics and Biophysics, also used a new process that had been developed at Münster University two years ago. This method involves transferring whole flies into a time-of-flight mass spectrometer in order to evaporate and then identify the substances directly on the body surface by means of a fine laser beam.
The scientists suspect that the composition of the hydrocarbon mixture on the flies' body surface provides information on the health and fertility of the other members of their species. They assume that fruit flies use the scent from possible mates in order to find healthy partners and assure their own offspring the best possible chances of survival. Based on this idea, the scientists hypothesize that younger flies are the better choice.
Kuo, T.-H., Yew, J. Y., Fedina, T. Y., Dreisewerd, K., Dierick, H. A. and Pletcher, S. D. (2012). Aging modulates cuticular hydrocarbons and sexual attractiveness in Drosophila melanogaster. J. Exp. Biol. 215, 814-821. DOI: 10.1242/jeb.064980
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http://jeb.biologists.org/content/215/5/814 Original publication/"Journal of Experimental Biology"
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