The Fine Structure and Function of the Salivary Glands of Nucella Lapillus (Gastropoda: Muricidae)

The fine structure of the tubular and acinous salivary glands of Nucella lapillus (L.) has been studied and some histochemical and enzyme tests have been carried out. The clusters of subepithelial cells of the tubular glands secrete a glycoprotein composed of chains of tubular macromolecules resembling secretions known to have adhesive properties which may assist in boring. The secretion is rich in disulphide groups, as are many toxins, and is believed to be responsible for the recently demonstrated pharmacological activity of the glands. It is proposed that flaccid paralysis is induced in prey by envenomation with this secretion during rasping, after soft parts have been exposed by an ‘anti-predator’ reaction to secretion from the hypobranchial gland of Nucella. The secretory vesicles of both types of gland cells in the acinous glands have heterogeneous contents indicating that their secretions are complex. The major component in those of the mucous cells is an acid mucopolysaccharide typical of a lubricant or releasing agent. The ciliated basal cells resemble typical enzyme-secreting cells and the major constituent of their secretion is a finely granular glycoprotein.