The Host-Parasite Interface of Cyathocotyle bushiensis Khan, 1962 (Trematoda: Strigeoidea) II. Electron Microscope Studies of the Tegument

Abstract

Ultrastructural observations indicate that the general tegument of Cyathocotyle bushiensis (Trematoda: Strigeoidea) contrasts markedly with the microvillous surface of the adhesive organ. This general tegument (approx 2 to 6 [mu] thick) is cytoplasmic and is in continuity with tegumentary cells lying below the basement layer. The tegument is bounded on its outer surface by a trilaminate plasma membrane, outside of which is a layer of electron-dense granular material. Within the cytoplasmic matrix occur spines possessing a lattice structure, mitochondria, and secretion bodies. Nuclei and endoplasmic reticulum appear to be absent and plasma membranes representing the lateral boundaries of cells have not been observed in the matrix. The secretion bodies (approx 0.16 to 0.2 [mu] diam) are present also in the extensions of the tegumentary cells penetrating the basement layer and in the cytoplasm of the tegumentary cells. The basal plasma membrane of the tegument is elevated into folds which project into the matrix. Below this membrane lies the basement layer. This consists of an upper less dense zone (approx 0.03 [mu] thick) separated from the thick (approx 0.3 to 0.4 [mu]) layer of fibers (approx 100 A diam) by a very narrow dense band. The basement layer is penetrated by cytoplasmic extensions from the tegumentary cells and by nerves running to sense organs in the tegument. In the region of the adhesive organ lobes the general tegument gradually alters to form the specialized microvillous surface. The concept of regional specialization of the tegument is discussed.