Postembryonic development of mating behavior in the male cricket Gryllus bimaculatus DeGeer

Abstract

The intact male nymph cricket, Gryllus bimaculatus DeGeer, was found to show mating-like behavior, that is, courtship-like behavior (CSLB) and copulation-like behavior (CPLB), in the 7th and 8th (last) instars. The 8th instar nymph exhibited less CSLB and CPLB than the adult but much more than the 7th instar nymph. The movement patterns of CSLB and CPLB were essentially the same as those of adults except for motor acts requiring the use of the genitalia. CSLB was short and often ceased spontaneously before it switched to CPLB. CPLB also ended earlier than in adults. The occurrence of CSLB and CPLB was almost zero the few days around ecdysis. The nymph was very sensitive to disturbance, so that he often stopped courtship for more than 30 min after stimulation. CSLB was similarly induced in the male nymph (8th instar) by pairing with a female adult, male adult, female nymph (8th) and male nymph (8th). The female nymph (8th) was observed to mount not only the male adult but also the male nymph (8th). A fixed time sexual refractoriness forming a basis of cyclical mating activity was not present after CPLB in the nymph. It appeared in association with the emergence of spermatophore protrusion behavior around day 3 after the imaginal molt. In fledglings, there were some transitions during the sexual maturation process, such as failures in hook hanging, spermatophore extrusion, and spermatophore transfer to the female. The decerebration experiments on nymphs and fresh adults agreed with behavioral observations. These results suggest that the development of mating behavior in the male cricket is a process of enhancement of basic motor patterns but not a process of addition of new movements by changes in pattern generation circuits in the central nervous system.