Orange-spotted grouper (Epinephelus coioides) orexin: Molecular cloning, tissue expression, ontogeny, daily rhythm and regulation of NPY gene expression

► Grouper orexin was identified by cDNA cloning. ► The prepro-orexin mRNA was widely present in brain and peripheral tissues. ► The prepro-orexin mRNA was first detected at the neural stage of grouper embryo. ► Grouper hypothalamic prepro-orexin mRNA significantly increased at the meal-time. ► Grouper orexin-A can stimulate NPY mRNA expression in vivo and in vitro.