Ecdysteroid and juvenile hormone changes in Bombyx mori eggs, related to the initiation of diapause

We describe a method for the routine determination of changes in juvenile hormone levels in insect eggs. The hormones are first converted into their diol derivatives, then they are purified from other lipids and separated by high-performance liquid chromatography (HPLC). The radioimmunoassay of the fractions was then determined. The method permits the simultaneous assay of ecdysteroids, and it was used for determining the hormonal changes in Bombyx eggs during the pre-diapause development. Our major finding is that the hormonal content of eggs dramatically increased prior to the initiation of diapause. This hormonal rise included ecdysone, 20-OH-ecdysone and 3 juvenile hormones. The HPLC retention time of the latter corresponded to JH₁ JH₂ and JH₃. Subsequently, the embryos entered diapause and the hormonal content of eggs was reduced to traces of ecdysteroids. These dramatic changes in juvenile hormone levels during early embryogenesis raise a number of issues which are developed in the discussion.