Abstract
In insects, the search for food is highly dependent on olfactory sensory input. Here, we investigated whether a single key odorant within an odor blend or the complexity of the odor blend influences the attraction of Drosophila melanogaster to a food source. A key odorant is defined as an odorant that elicits a difference in the behavioral response when two similar complex odor blends are offered. To validate that the observed behavioral responses were elicited by olfactory stimuli, we used olfactory co-receptor Orco mutants. We show that within a food odor blend, ethanol functions as a key odorant. In addition to ethanol other odorants might serve as key odorants at specific concentrations. However, not all odorants are key odorants. The intensity of the odor background influences the attractiveness of the key odorants. Increased complexity is only more attractive in a concentration-dependent range for single compounds in a blend. Orco is necessary to discriminate between two similarly attractive odorants when offered as single odorants and in food odor blends, supporting the importance of single odorant recognition in odor blends. These data strongly indicate that flies use more than one strategy to navigate to a food odor source, depending on the availability of key odorants in the odor blend and the alternative odor offered.
Highlights
Like other insects, Drosophilidae Drosophila melanogaster meigen 1830 searches for food using the olfactory system
To test whether Orco is required for single odor recognition within a food odor blend, we examined whether Orco1 mutants distinguish between a food odor and a food odor with different concentrations of EtOAc, acetic acid (AA) and AP (Figure 2; Supplementary Figure S1)
We provide evidence that flies recognize specific odorants within the food odor bouquet based on their identity and that the concentration of these odorants determines the attractiveness of the food odor blend
Summary
Drosophilidae Drosophila melanogaster meigen 1830 searches for food using the olfactory system. A putative food source such as a fruit emits multiple volatile compounds with varying concentrations and compositions. The smell of an apple contains more than 100 different volatile compounds (Ferreira et al, 2009). This bouquet changes in composition and complexity during ripening and is characteristic of specific maturity states (Mehinagic et al, 2006). Microorganisms contribute their own specific smells to the fruit odor blend. The attraction of flies to ethanol-containing food odors raises the question of whether the smell
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