Substances related to vertebrate peptidic hormones have been searched by immunohistochemical methods in Pecten maximus . Neurosecretory cells have been detected in the nervous ganglia with antisera raised against vertebrate hormones, gastrin/CCK like, glucagon like, insuline like, somatostatine like. Other gastro-intestinal hormones like are localized in some cells of the gut epithelium: bombesine and vasoactive intestinal peptide.