PROFILE OF EMBRYONIC ECDYSTEROIDS IN THE DECAPOD CRUSTACEAN, MACROBRACHIUM-ROSENBERGII

The ecdysteroid composition of embryos of M. rosenbergii at various st ages of embryogenesis has been studied by means of radioimmunoassay (R IA), high-performance liquid chromatography - RIA (HPLC-RIA) and gas c hromatography/mass spectrometry (selected ion monitoring; GC/MS(SIM). In newly-laid eggs, only free ecdysteroids (ecdysone and 20-hydroxyecd ysone) were detected, whereas eggs at an early stage of embryogenesis contained ecdysone and also low levels of apolar ecdysteroid conjugate s. Mid stage embryonating eggs contained comparatively high levels of both free ecdysteroid (ecdysone, 18.3ng/g) and apolar conjugates (20.9 ng/g). Late embryos contained by far the highest overall level of ecdy steroid, indicating the ability of the developing embryo to synthesize ecdysteroid. In contrast to the other stages, late embryos contained 26-hydroxyecdysone, ecdysonoic acid and 20-hydroxyecdysonoic acid at r elatively low levels and 2,3-diacetylecdysone 22-phosphate at a compar atively high level (324.0 ng/g). These results suggest that the develo ping embryo of M. rosenbergii is capable of both ecdysteroid biosynthe sis (presumably for utilization during specific stages of embryogenesi s), conversion into apolar conjugates and inactivation by conversion i nto 26-oic acids and polar conjugates.