How Drosophila Detect Volatile Pheromones: Signaling, Circuits, and Behavior

Pheromones are chemicals released from one individual to influence the behavior of another animal of the same species (Karlson and Luscher 1959). Detection of these pheromones can produce broad developmental or endocrine changes (priming pheromones) or elicit specific behaviors (releaser pheromones). Releaser pheromones elicit innate behaviors in the receiving individual, and are widely used in the animal kingdom, often to guide mating behavior toward appropriate partners. Pheromones are used to guide social interactions in both vertebrate and invertebrate animals. The social insects (ants, bees, and termites) have taken great advantage of pheromone signaling to create a chemical language that guides an array of behaviors and developmental programs essential for the overall functioning of the colony (reviewed in Alaux et al. 2010). Therefore, understanding how pheromones are detected and how this information is ultimately converted into specific behaviors is of great interest. In this chapter we focus on volatile insect pheromone detection and processing. Insects are well known to have exquisite sensitivity to pheromones. For example, sex pheromones released from female moths attract male mating partners over great distances (Carde and Willis 2008; Fabre 1916), and males can detect single molecules (Kaissling and Priesner 1970). How this remarkable sensitivity is achieved remains poorly understood. Studies utilizing have been instrumental in elucidating the molecular mechanisms underlying volatile pheromone transduction (reviewed in Ha and Smith 2009; Ronderos and Smith 2009; Smith 2012; Vosshall 2008). Here we review recent progress in understanding the detection and neuronal circuitry underlying behaviors elicited by the releaser pheromone 11--vaccenyl acetate (cVA). In addition, the neuronal circuits activated by cVA are beginning to be worked out. We discuss recent findings suggesting that the mechanisms for detection of contact (taste) pheromones (including cVA) are distinct from those used for volatile pheromones. Finally, to put these findings in the larger context, lessons learned in the fruit fly are likely to be relevant to other insect pheromone systems, and may reveal general principles underlying pheromone-induced behaviors in all animals. This information will provide the basis for novel approaches that are more selective than chemical pesticides to control insect species that cause human disease and inflict crop damage.