Neurohormonal control of the instinctive behavior in the male cricket.

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Male field crickets Gryllus bimaculatus exhibit stereotyped sexual behavior when they encounter conspecific females and aggressive behavior against males. To understand the neuronal and hormonal mechanism of the instinctive behavior, the factors affecting sexual and aggressive motivation were investigated. Behavioral analysis and neurobiochemical experiments revealed that at least two neurohormones from the brain and the mesothoracic ganglion reciprocally control the elicitation of the sexual behavior and provide an appropriate interval in the mating sequence of the male cricket. Octopamine and serotonin are possible candidates for these neurohormones. On the other hand, in order to investigate the aggressive behavior, some of crickets were isolated in transparent cases (Internet crickets) and others remained crowded. In the fights between crowded crickets, most of them quickly exhibited dominance- subordinance interactions. On the other hand, in the fights between isolated ones, prolo … More nged intense fights were frequently observed. In the fights of isolated versus crowded, most isolated crickets won at the level as intense as the fights of both isolated ones. The aggressiveness and the duration of fights were dependent on the period of isolation. In particular, Internet crickets exhibited abnormal aggressiveness. The mating behavior developed after imaginal eclosion. Isolated males matured 6 days after imaginal eclosion, whereas crowded ones matured 3 days. Although crowded males never attacked females, Internet crickets attacked them with abnormal aggressiveness. The attack of Internet crickets to females continued until 3 days after imaginal eclosion and disappeared 6 days after. Abnormal aggressiveness of the Internet cricket suggests that the tactile communication play an important role in the development of their aggressive and mating behavior. Neurobiochemical analysis of the aggressive behavior suggests that the distribution of biogenic amines in the brain depends upon the social experience and composes the basis of aggressiveness. Less