Post-mating sexual abstinence in a male moth

Abstract

In most animals, male copulation is dependent on the detection and processing of female-produced sex pheromones. In males, a refractory postejaculatory interval (PEI) follows copulation, allowing them to avoid direct remating until they have replenished their reproductive tracts. In the moth Agrotis ipsilon, newly mated males show a transient inhibition of behavioral and central nervous responses to sex pheromone. Using non-pheromonal (plant) odors, pheromones and their mixture, we now show that the observed lack of pheromone response originates from differential post-mating odor processing in the brain. Although mated males still respond to plant odors alone, their response to mixtures depends on the added pheromone concentration. Below a specific threshold, sex pheromone is not detected at the brain level; above this threshold, it becomes inhibitory. This PEI can thus be interpreted as a «refusal to respond», which contradicts the generally accepted paradigm of sleep-like/exhaustion behavior during PEI.