Gland cells associated with the alimentary tract of a monogenean, Diclidophora merlangi

Abstract

Three distinct groups of unicellular glands open into the buccal cavity, prepharynx, and oesophagus, respectively, of Diclidophora merlangi. Buccal glands produce a dense, acidophilic secretion of protein-rich droplets that are discharged from duct-like extensions of the glands by eccrine secretion. Prepharyngeal glands are extensive and contain basiphilic secretory droplets of varying density and characterized by the presence of one or two dense core-like inclusions. The droplets are PAS-positive and reactive for protein, and accumulate in the gland cell apices which form part of the lining to the prepharynx lumen. They are released in large numbers by apocrine secretion or, individually, by an eccrine secretory mechanism. Oesophageal glands are acidophilic and contain electronlucid, PAS-positive droplets that develop a crystalline appearance prior to release via either eccrine or apocrine secretion. Differences in ultrastructure and histochemistry indicate the glands are also functionally separate, and their probable role in feeding and extracellular digestion of blood in the worm is discussed.