Brain control of mating behavior in the male cricket Gryllus bimaculatus DeGeer: brain neurons responsible for inhibition of copulation actions

We localized brain neurons responsible for the inhibition of copulation actions in the male cricket, Gryllus bimaculatus. Males with one connective-cut between the brain and the terminal abdominal ganglion (TAG) were able to perform normal reproductive behaviors such as courtship, copulation and spermatophore protrusion. However, copulation response tests using a female dummy showed that they failed to exhibit a transient inhibitory state after application of noxious stimulation in the mating stage and to exhibit a tonic inhibitory state in the post-copulatory sexual refractory stage. A partial cut of a single connective (hemilateral connective-cut) combined with the copulation response test and an axonal backfilling demonstrated that approximately 40 brain neurons (per one connective), whose somata were located in the posterior region of the protocerebrum and mainly contralaterally to their descending axons running through the dorso-medial part of the connective, were candidates for the inhibition of copulation actions, at least in the mating stage. In addition, we report here for the first time, that copulation actions can be elicited shortly after copulation even in intact males. This unusual behavior was frequently observed in fledglings after the final molt. The results are discussed from the perspective of the operation of the brain inhibition system on the central pattern generator (CPG) for copulation.