| Abstract : |
Social cues such as conspecific pheromones have a profound impact on foraging choice. The fruit fly Drosophila melanogaster aggregates on food sources previously visited by other flies due to the deposition of the pheromone, 11-cis-vaccenyl acetate (cVA), on food surfaces. Using a high throughput food search assay, we show cVA dramatically enhances behavioral attraction in fruit flies when present in odor-pheromone mixtures with either vinegar or 2,3 butanedione but not when presented alone. We also show odor-odor mixtures of vinegar and 2,3 butanedione can enhance behavioral attraction, as well. Are the neural mechanisms underlying attraction to odor-odor mixtures and odor-pheromone mixtures fundamentally different from one another? To investigate this question, we measured dose-responses for behavioral attraction to odor-odor and odor-pheromone mixtures. We found that enhanced behavioral attraction to the odor-pheromone mixture persists over a larger range of concentrations than the odor-odor mixture. This suggests the neural mechanisms for attraction to the odor-odor mixture may differ from the odor-pheromone mixture. How might a social cue like cVA modulate olfactory sensitivity to a food odor? The male pheromone, cVA activates the Or67d odor receptor neurons (ORNs) that relay to the DA1 ventral and lateral projection neurons. Silencing either the Or67d ORN or the DA1 ventral projection neurons impaired enhanced attraction to the odor-pheromone mixtures. Silencing the DA1 lateral projection neurons had no effect. This suggests that information about cVA is relayed through the ventral projection neurons which are GABAergic and project directly to the lateral horn. This suggests that the pheromone may enhance attraction via an inhibitory mechanism in the lateral horn. |