Ecdysteroids During Embryogenesis in<i>Locusta migratoria</i>

Abstract

SYNOPSIS. Ovaries of &lt;it&gt;Locusta migratoria&lt;/it&gt; synthesize large amounts of ecdysteroids at the end of oöcyte maturation. The predominant ecdysteroids in mature ovaries are conjugated 2-deoxyecdysone (100 μM) and conjugated ecdysone (50 μM) which outnumber the corresponding free compounds by 50–100 fold. These various ecdysteroids persist during ovulation and are recovered from newly-laid eggs. The conjugated maternal ecdysteroids are gradually metabolized as embryonic development proceeds; they have disappeared as such on day 6 after oviposition, that is after blastokinesis and shortly after dorsal closure. Concomitantly to this metabolism of the maternal conjugated ecdysteroids, other ecdysteroid conjugates appear in the eggs which have different chromatographic behaviors and some of which are conjugates of ecdysone metabolites formed by the embryo. The data available so far are compatible with the hypothesis that the maternal conjugates are hydrolysed to free 2-deoxyecdysone and ecdysone by the embryo during early stages of development and subsequently conjugated to inactivation compounds. During the later stages of embryonic development however, a &lt;it&gt;de novo&lt;/it&gt; synthesis of ecdysone is probable, the maternal conjugates having been metabolized during the earlier stages.