ECDYSONE METABOLISM AND THE INTERRUPTION OF PROECDYSIS IN THE LAND CRAB,GECARCINUS LATERALIS

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Abstract
The metabolic fate of injected [3H]ecdysone was examined in crabs in premolt stage Do and in crabs at this stage whose proecdysis was interrupted by re-autotomy of partially regenerated limbs at the time of injection. In both sets of crabs, 20-hydroxyecdysone was the principal metabolite, with further hydroxylation to 20,26-dihydroxyecdysone and the formation of polar conjugates (primarily in the midgut gland) occurring to a limited extent. The rate of elimination of 20-hydroxyecdysone from normal crabs in stage Do is slow (k = 0.002/h). Within a few hours after re-autotomy of partial regenerates from crabs in stage Do, the rate of loss of 20-hydroxyecdysone from the whole crab increases by 10-fold, while the loss from the serum accelerates 20-fold. The increased rate of loss of 20-hydroxyecdysone from the re-autotomized crabs is associated with an increased amount of catabolism to polar inactivation products. The increase in the rate of elimination of ecdysteroids is sufficient to account for the observed decrease in endogenous ecdysteroid titers when proecdysis is interrupted by this re-autotomy.