Charmantier, G.
Y organs are present in the first post-embryonic instar in all investigated species of stomatopods, euphausiaceans and decapods, and in the embryos of some decapods. Mandibular organs have also been observed in the first larval instar of several decapods. Neuroendocrine cells are present in the X-organ of first larvae or of embryos of stomatopods and decapods; the sinus gland is also generally present at hatching.
There is evidence for the implication of Y organs in the control of larval molting (histological changes and variations in ecdysteroid titers related to molt cycle), although some results are unclear (variable effects of 20-hydroxyecdysone according to stages) or lacking (no direct evidence from ablation). There is also experimental or immunocytochemical support for MIH regulation of molting through the X-organ sinus gland complex (variations of ecdysteroid titers induced by eyestalk removal or injection of extracts, presence of putative MIH in X-organ and sinus gland) but the effect of eyestalk removal on intermolt duration is variable. Other neuropeptides of the same family, CHH and VIH, have been localized in the eyestalks of early postembryonic stages but their function is unknown as yet. Experimental evidence for an eyestalk control of metamorphosis exists in some decapods, but its process is still unknown. The presence of (a) chromatophorotropin(s) in the larvae of decapods has been suggested through eyestalk removal. Hydromineral regulation is regulated through eyestalk neuroendocrine centers in larvae and postlarvae of several decapods, but the implicated factor is still unknown.
(Laboratoire d'Ecophysiologie des Invertebres, Universite Montpellier II, pl. E. Bataillon, 34095 Montpellier cedex 05, France)
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