Elevated Ecdysteroid Titer and Precocious Molt and Vitellogenesis Induced by Eyestalk Ablation in the Estuarine Crab, Metopograpsus Messor (Brachyura: Decapoda)

Abstract

Abstract Premolt and vitellogenesis are mutually exclusive events in the wild population of the brachyuran crab, Metopograpsus messor; active vitellogenesis occurs only in intermolt females, at a relatively low ecdysteroid profile, judged from radioimmunoassay. Bilateral eyestalk ablation, however, has resulted in simultaneous precipitation of premolt and ovarian growth in the same crab, thus severing the normal antagonistic programming of these two high-energy demanding processes. This result argues for the necessity of eyestalk principles in maintaining the normal (antagonistic) programming of growth and reproduction in the species. Ovaries of the eyestalk ablated crabs precociously accumulate yolk and the oocytes could attain the size of a fully grown egg within 10 days post-ablation. The eyestalk ablated females have also shown dramatic rise in haemolymph ecdysteroid levels, even surpassing the levels (P < 0.05) of the normal premolt individuals, revealing that ovarian growth can occur under a high ec...