Effects of exogenous ecdysterone upon moulting, proecdysial development, and limb regeneration in the prawn Palaemon...

Injection of small doses of ecdysterone accelerated moulting and proecdysis in the prawn Palaemon elegans. Injection of large doses of ecdysterone (1-10 micrograms) markedly accelerated proecdysis, but death always occurred prior to or during moulting and was accompanied by abnormal setal development and retarded cuticle formation. Dose-response curves were obtained for a range of hormone doses from 10 to 0.01 micrograms by administering ecdysterone during postmoult (stages A-B) and early premoult (stages DE0-DL0). Accelerated proecdysis and viable moulting were more marked in the group injected during early premoult (stages DE0-DL0). The sensitivity threshold for prawns injected during this time was less than 40 ng g-1 but could not be determined more precisely in view of the range of ecdysterone concentrations used. In contrast, the sensitivity threshold for ecdysterone administered during postmoult (stages A-B) was much higher, between 0.4 and 2 micrograms g-1. The possible mechanisms controlling sensitivity thresholds for ecdysterone are discussed. The effect of ecdysterone on limb regeneration was also studied. Within the concentration range used, ecdysterone was found to have no effect on the rate of limb regeneration.