An electron microscope study of the tegument and associated structures of Proteocephalus pollanicoli

Abstract

The tegument of Proteocephalus pollanicoli is organized at two levels. The external level is a syncytial layer of protoplasm composed of vesicles in a granular matrix. The surface of this level has microvillus-like structure, microtriches, with sharp electron dense tips and less dense bases. Pinocytotic vesicles, large vacuoles, and evaginations occur at the surface of the external level, whereas mitochondria and lipid droplets tend to be concentrated basally. The basal plasma membrane has in some places small invaginations and at others large evaginations forming protoplasmic tubes which connect the external and internal levels.The internal level is composed of individual areas of dense, granular protoplasm, each of which has a nucleus. These areas, or cuticular cells, contain lipid droplets, mitochondria, short lengths of agranular endoplasmic reticulum and phospholipid bodies. Two cuticular cells lying close together may be joined by a protoplasmic bridge and thereby form a limited syncytium.The morphology of the tegument of this proteocephalid is compared with that of the cyclophyllidean species and the function of the tegument in parasitic helminths is discussed.I should like to acknowledge the technical assistance of Mr W. Ferguson and Mr A. Lyness. My thanks are also due to the Wellcome Trust for a grant to purchase the Akashi Transcope and ancillary equipment.