Effects of bilateral eyestalk ablation on molting and ovarian development in the giant freshwater prawn, Macrobrachium rosenbergii

In the present study, the effects of bilateral eyestalk ablation on molt interval, ovarian development, and hemolymph levels of ecdysteroid and vitellogenin were investigated in the giant freshwater prawn, Macrobrachium rosenbergii in order to examine the roles of the eyestalk hormones. In destalked males and females, ecdysteroid levels increased rapidly, and molt intervals were significantly shortened in comparison with control non-destalked prawns. All destalked females exhibited a reproductive molt cycle accompanied by ovarian development and oviposition even under continuous hemolymph sampling. In contrast, in control females, the percentages of animals undergoing a reproductive molt cycle were 69 and 51% with and without sampling, respectively. The duration of ovarian development was shortened in the destalked females. These results indicate the inhibitory roles of the eyestalk hormones on molting and vitellogenesis. On the other hand, after eyestalk ablation, male prawns molted more than twice, and destalked females showed a correlation of vitellogenin level to molt stage similar to control reproductive females. These results indicate that the molt cycle and the correlation between vitellogenesis and molting are maintained in the absence of eyestalk hormone regulation.