METABOLISM OF 3-DEHYDROECDYSONE IN THE CRAYFISH ORCONECTES-LIMOSUS (CRUSTACEA, DECAPODA)

3-Dehydroecdysone (3DE) is the major secretory product of crayfish mou lting glands. The metabolic fate of 3DE in the crayfish Orconectes lim osus was investigated after in vivo injection of [H-3]3DE and after in cubation of various tissues with [H-3]3DE in vitro. Metabolites in who le body and tissue extracts were analysed by HPLC. In vivo [H-3]3DE is efficiently reduced and hydroxylated to [H-3]20-hydroxyecdysone (20E) , which is one of the major metabolites observed in our study and also the major circulating ecdysteroid. 3 beta-reduction and 20-hydroxylat ion were the predominant enzymatic activities obtained after in vitro incubation of [H-3]3DE with various tissues. Under the conditions util ised here, antennal glands and CNS (abdominal ganglia) exhibited highe st reductase activity per mg wet weight; epidermis, gonads, midgut gla nd and hindgut had moderate activities; muscle had the least and hemol ymph was inactive. 3DE conversion by Y-organs differed moulting stage dependently. 20-hydroxylation activities were similarly distributed in all organs except for ovaries, in which 20-hydroxylation exceeded the 3 beta-reduction. Ovaries were also the only tissue containing a sign ificant 3 alpha-reductase activity.