Secretory glands of the snail tentacle and their relation to the olfactory organ (Mollusca,Gastropoda)

Summary The epidermis of the posterior tentacles of the terrestrial snail Achatina fulica was examined by histological and histochemial methods. There are seven types of unicellular glands in the tentacle skin: three mucocytes containing either acid mucopolysaccharides or neutral mucopolysaccharides, or both; two mucocytes containing glycoproteins; a lipid gland; and a protein gland. The mucocytes are considerably more abundant along the shaft of the tentacle than at the tip, where the olfactory organ is situated. Conversely, the lipid glands and the protein glands are found almost exclusively in the olfactory organ. With minor exceptions, none of the foregoing cell types is present in the skin of the head or the foot. These observations indicate a high degree of local specificity in secretory products, consistent with a ubiquitous and generous endowment of glands in the molluscan skin. Collar cells, described by previous authors in closely related species, were not observed.