Mechanism of individual recognition by learning/memory/experience and plasticity of microbrain

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Effects of aging, juvenile hormone and social stimuli on the development and plasticity of learning capability of the honeybees were analyzed.・ The learning ability was acquired 5 to 9 days after emergence in workers, while it was accomplished 2 to 5 days after emergence in drone.・ Volumes of the subcompartments of mushroom body were compared between the bees experienced the various stimuli in the hive and the bees deprived of these stimuli in the confined condition by using semithin sections. There were significant quantitative differences in the antennal lobe and some subcompartments of the mushroom body.・ Juvenile hormone was found to have distinct promotive effect on the development of learning capability but the action was indirect.・ Timing of birth of the Kenyon cells in adult development was compared between worker and queen castes by the immunohistochemical method using BrdU incorporation. It was distinctly earlier in the queen caste in honeybees.・ Field studies were done in arctic Norway (latitude of 70N) to see the presence or absence of bumble bee foraging activities in the bright night of midnight sun, in relation to the phenomenon of continuous and restless activities found under the continuous light in the laboratory. Bees were foraging even in the midnight, and the threshold light intensity allowing the masking of circadian rhythmicity was lower than that in Japanese bumble bees.The phenomenon was proved to be the adaptation to extraordinary long day climate.