Developmental Changes of Ecdysteroids in the Eggs of the Silkworm, Bombyx mori

Ecdysteroids were studied in relation to embryonic development and diapause of the silkworm, Bombyx mori. The majority of the ecdysteroids was found to be in the conjugated form, and minor part, in the free form. In the developing eggs, 2-deoxyecdysone, 2-deoxy-20-hydroxy-ecdysone and 3-epi-ecdysone were found to have the free ecdysteroid form as well as the conjugated ecdysteroid form. Ecdysone and 20-hydroxyecdysone almost exclusively had the conjugated form. The concentration of ecdysteroids in the embryo was higher than that in yolkplasm in the early embryonic stages. During the embryonic diapause, the concentration of free ecdysteroids decreased to a low level while the conjugated form maintained the original level.