Reproductive Behavior and Physiology in the Cricket Gryllus bimaculatus

Abstract

Gryllus bimaculatus males have a reproductive cycle consisting of a mating stage and a sexually refractory stage. During the mating stage, the male exhibits distinct behavior that encompasses three main stages: calling, courtship, and copulation. The last stage, copulation, is carried out in a fixed manner by the stimulus-response chain. The final copulatory act, spermatophore extrusion, is caused by stimulation of mechano-sensilla in the epiphallus during genitalia coupling, which terminates the mating stage. The sexually refractory stage starts with spermatophore extrusion, during which the male is rather aggressive and does not exhibit any mating behavior. A male first shows spermatophore preparation when stimulated by the female, then forms the new spermatophore, and finally recommences the calling song, i.e., the start of the mating stage. Physiological investigations reveal that the male mating behavior is mainly controlled by the brain and the terminal abdominal ganglion (TAG), which exerts three types of inhibition on the pattern generators for mating behavior. The brain also facilitates sexual excitation via octopamine. One of the conspicuous features of the reproductive behavior in Gryllus bimaculatus is that the sexually refractory stage between spermatophore preparation and the start of calling song is time fixed at around 1 h. Experiments utilizing the targeted cooling of the central nervous system indicate a presence of a time-measuring mechanism (“timer”) that is located within the TAG. Long-term spike recordings of neurons also support the presence of such a timer within the TAG. Finally, the occurrence of mating-like actions in larval nymphs is discussed. All of these findings have now generated a large body of work that will help establish Gryllus as a new experimental system for studying reproductive behavior and physiology in crickets and other insect species.