The Presence of 20-Hydroxyecdysonoic Acid and Ecdysonoic Acid in Eggs of the Giant Freshwater Prawn Macrobrachium rosenbergii

High polarity products (HPP) are observed to increase dramatically during the embryogenesis of Macrobrachium rosenbergii; in this investigation, their identity was examined employing high performanceliquid chromatography (HPLC) and radioimmunoassay (RIA). 20-Hydroxyecdysonoic and ecdysonoicacid were seen to comprise over 70% of total HPP immunoreactivity. Conjugates of 20-hydroxyecdysone, inokosterone, and ecdysone accounted for up to 25% of HPP immunoreactivity, and 20, 26-hydroxy-ecdysone comprised less than 5%. Therefore, as development proceeds, the acidic 26-oic derivativesbecome the dominant ecdysteroid species. It has been postulated on the basis of this investigationthat 26-oic derivative formation is the major route of ecdysteroid inactivation; concommittantlyincreasing 20-hydroxyecdysone and 20-hydroxyecdysonoic acid titres and observed low quantities of 20, 26-dihydroxyecdysone suggest the rapid conversion of active hormones to 26-oic derivatives. Conjugate formation may also be a route of ecdysteroid inactivation. These pathways may be importantin controlling the titres of active ecdysteroids within the egg, and are possibly manifested by the ac-cumulation of metabolites during embryogenesis.