Neurophysiological study of sexual dimorphism of the nervous system of crickets and its differentiation during postembryonic development

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Sexual dimorphism of the terminal abdominal ganglion (TAG), its target organs and flight muscles of the cricket (Gryllus bimaculatus) was studied, and the results obtained as follows;1. Sexual dimorphism was found in the morphological characteristic and number of dorsal unpaired median (DUM) neurons of TAG as well as in those of ventral unpaired median (VUM)neurons, especially VUM neurons running bilaterally through the second on seventh nerve roots.2. About 130 DUM neurons of TAG of male adult extend their axons bilaterally and innervate the muscles of accessory glands (AGs) and edjaculatory duct.3. The studies using HPLC and bioassay showed that proctolin is present in the normal AGs with the innervation of DUM neurons, whereas it is not present in the transplanted AGs which developed the muscles without innervation of DUM neurons in the host. These studies also revealed that a certain amount of proctolin is detectable in the surrounding medium of AGs while the muscles of AGs contrac … More t in response to electrical stimulation of DUM neurons or high concentration of KCl.4. It was found that a certain type of secretory granules of AGs contain serotoninlike materials, and that serotonin is present in the spermatophore. These findings and the preliminary experiment of the action of serotonin on the spermathecal duct imply that serotonin secreted from AGs is transferred with spermatozoa to female via the spermatophore during copulation, and it induces the rhythmic contraction of the spermathecal duct for the migration of spermatozoa to the spermatheca.5. Age-related changes (growth and degeneration) in the flight muscles were remarkable in both sexes after the imaginal molt, and such changes began to occur as the flight muscles started to degenerate according to sex-dependent patterns. For example, in both sexes the weight of the elevator muscle(M90; stridulatory muscle in male) of the forewing wing increased during maturation after imaginal molt and it reached the maximum value gradually. After that, in male the weight of muscle was almost unchangeable, while in female it decreased quickly. Less