Is Drosophila melanogaster Stress Odorant (dSO) really an alarm pheromone?

Social interactions are crucial for the reproduction and survival of many organisms, including those using visual, auditory and olfactory cues to signal the presence of danger. Drosophila melanogaster emits an olfactory alarm signal, termed the Drosophila stress odorant (dSO) in response to mechanical agitation or electric shock, and conspecifics avoid areas previously occupied by stressed individuals. However, the contextual, genetic and neural underpinnings of the emission of, and response to dSO, have received little attention. Using a binary choice assay, we determined that neither age and sex of emitters, nor the time of the day, affected the emission or avoidance of dSO. However, both sex and mating status affected the response to dSO. We also demonstrated that dSO was not species specific so it should not be considered a pheromone but a general alarm signal for Drosophila. However, the response levels to both intra and inter-specific cues differed between species and possible reasons for these differences are discussed. HIGHLIGHTSO_LIEmission of dSO, a highly volatile chemical blend emitted by stressed flies, is not context specific C_LIO_LIResponse to dSO is context specific, affected by factors such as age and mating status. C_LIO_LIAs flies respond to volatiles for stressed heterospecifics, dSO should not be considered an alarm pheromone, but as an alarm cue. C_LI