Relationships between an Application of KK-42 and Pupal Developmemt in the Silkworm, Bombyx mandarina

概要

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Populations of Chinese origin of the silkworm, Bombyx mandarina, do not show arrested pupal stage, however populations of Japanese origin undergo pupal summer diapause. Hormonal control of this pupal summer diapause in Bombyx mandarina of Japanese origin was investigated using KK-42 treated pupae of Chinese origin. When an imidazole compound (KK-42:1-benzyl-5-[(E) 2, 6-dimethyl-1, 5-heptadienyl] imidazole) was injected into the newly ecdysed pupae of Chinese populations, the pupal-adult development was arrested for as long as 40 days. Resumption of pupal-adult development of the KK-42 treated pupae was induced by injection of 20-hydroxyecdysone (20-HE). Oxygen consumption of the KK-42 treated animals was very low comparing to the control but it increased gradually about 35 to 37 days after treatment. Abrupt increase of oxygen consumption was observed about 12hr after the application of 20-HE in the KK-42 treated animals. These results strongly indicate that the pupal summer diapause in Japanese populations of Bombyx mandarina is due to the low level of ecdysteroids in their body thus preventing them from proceeding to the pupal-adult development.