Fluctuations in hemolymph ecdysteroid levels during the reproductive and non-reproductive molt cycles in the giant freshwater prawn Macrobrachium rosenbergii

Hemolymph ecdysteroid levels were traced during the molt cycle in female gi ant freshwater prawn, Macrobrachium rosenbergii Levels were compared betwee n the reproductive molt cycle, accompanied by ovarian development and ovipo sition following ecdysis, and the nonreproductive molt cycle, marked by the absence of ovarian development, to examine the involvement of ecdysteroids in ovarian development. Total ecdysteroid levels determined by radioimmuno assay (RIA) showed similar fluctuation patterns between both molt cycles. L evels were low during postmolt stages A-B and gradually decreased to low ba sal levels at intermolt stages C-0-C-1. Levels then increased during premol t stages D-0-D-2, reached a large peak at the early D-3 stage, and declined sharply prior to ecdysis. In addition, ecdysteroids in the hemolymph were analyzed using highperformance liquid chromatography combined with RIA in o rder to identify individual ecdysteroid species. During both molt cycles, 2 0-hydroxyecdysone, ecdysone and high polarity immunoreactive products were detected, and 20-hydroxyecdysone was the most predominant ecdysteroid. Fluc tuations in all ecdysteroid species during each type of molt cycle parallel ed those of total ecdysteroid levels, and did not show significant differen ces between the reproductive and non-reproductive molt cycles. These result s suggest that ecdysteroids are not involved in ovarian development but in the molting process only.