Studies on the biosynthesis of ecdysone by the Y-organs of Carcinus maenas.

High specific activity tritiated ecdysone precursor, 2,22,25-trideoxyecdysone, was incubated with Y-organs from intermoult and premoult shore crabs. Several metabolites were identified among which ecdysone and 25-deoxyecdysone. The concomitant production of these 2 molecules by Y-organs and their subsequent hydroxylation at C-20 by peripheral tissues, provide an explanation for the presence of both 20-hydroxyecdysone and ponasterone A (25-deoxy-20-hydroxyecdysone) in the circulating haemolymph of crabs.