The Neural Circuitry that Functions as a Switch for Courtship versus Aggression in Drosophila Males

Courtship and aggression are induced in a mutually exclusive manner in male Drosophila melanogaster, which quickly chooses one of these behavioral repertoires to run depending on whether the encountered conspecific is a female or male, yet the neural mechanism underlying this decision making remains obscure. By targeted excitation and synaptic blockage in a subset of brain neurons, we demonstrate here that the fruitless (fru)-negative subfraction (∼20 cells) of a doublesex-positive neural cluster, pC1, acts as the aggression-triggering center whereas the fru-positive subfraction (∼20 cells) of pC1 acts as the courtship-triggering center, and that the mutually exclusive activation of these two centers is attained by a double-layered inhibitory switch composed of two fru single-positive clusters, LC1 and mAL. To our knowledge, this is the first report to unravel the cellular identity of the neural switch that governs the alternative activation of aggression and courtship in the animal kingdom. •Courtship and aggression are mutually exclusive repertoires in Drosophila males•The dsx-expressing pC1 cluster is composed of neurons with and without fru expression•fru(+) pC1 is dedicated to inducing courtship and fru(–) pC1 to inducing aggression•GABAergic LC1 inhibits the courtship center P1 and disinhibits pC1 for aggression Koganezawa et al. unravel a neural network that makes the immediate decision to court or contend with another fly upon first meeting. This network triggers courtship by initiating one signal “hit” and aggression by initiating two signal hits, making quick but safe decision making possible.