Nitroxidergic Cells in the Intestine of the Bivalve Mollusk Modiolus kurilensis

The distribution of nitroxidergic (NO-ergic) cells in the direct and recurrent loops of the midgut and in the hindgut of the bivalve mollusk Modiolus kurilensis was studied using a NADPH-diaphorase (NADPH-d) histochemistry [13]. Intraepithelial NO-ergic cells were found in the intestinal groove, in the major typhlosole of the direct loop, in the recurrent loop of the midgut, as well as in the hindgut. The apical processes of these cells are directed to the intestinal lumen, whereas the basal processes connect to the basiepithelial NO-ergic plexus. The latter, in turn, have separate fibers that are in contactswith the subepithelial NO-ergic plexus. Both plexuses are well developed in the intestinal groove of the direct loop and in the recurrent loop of the midgut, as well as in the hindgut. In the major typhlosole and crystalline style sac of the direct loop, both basi- and subepithelial NO-ergic plexuses are less developed. In the minor typhlosole, the basiepithelial NO-ergic plexus is absent and only single fibers of the subepithelial plexus occur. In the connective tissue and muscular layers of the recurrent loop of the midgut, subepithelial NO-ergic nerve cells were found.