Ultrastructure of the Pharynx and Some Parenchyma Cells of Zeuxapta-Seriolae and Paramicrocotyloides-Reticularis (Monogenea, Polyopisthocotylea, Microcotylidae)

Abstract

The ultrastructure of the pharynx of Zeuxapta seriolae and Paramicrocotyloides reticularis (Monogenea : Microcotylidae) is described. The pharynx of both species is surrounded by a thick sheath resembling a basal lamina. It contains layers of longitudinal, circular and radial muscles, glandular cells, smaller cells interpreted as connective tissue cells, axons, and loose connective tissue. The cell bodies of the glandular cells are subdivided by deep invaginations of cell membranes; the cytoplasm is rich in granular endoplasmic reticulum and golgi complexes. The pharyngeal lumen is branched and lined with a layer of cytoplasm which contains numerous surface lamellae, branched 'supportive' lamellae, and vesicles. A body consisting of stacks of tubules, and associated with axons, is interpreted as a proprioceptor. Bacteria were found in the cytoplasm of some parts of the pharynx of Z. seriolae, particularly near the lumen. In Z. seriolae, three types of parenchyma cells near the pharynx were examined. All have deep invaginations of the cell membrane which, at least in some cells, are anchored near the nucleus by means of desmosomes, and which contain processes of adjacent cells.