Light and Electron Microscopic Study of Balantidium entozoon (Ciliophora, Vestibuliferida)Somatic Cortex and Vestibular Cavity

Abstract

The somatic cortex and the vcstibulum of Balantidium entozoon were studied using silver carbonatc impregnation and electron microscopy. The somatic infraciliature is composed by monokinetids with a short kinetodesmal fiber, a long posteiliary microtubular ribbon, and a long transverse microtubular ribbon directed anteriorly. Moreover, the somatic kinetids located near the vestibular aperture bear nematodesmal bundles (“oralized somatic kinetids”) that contribute to form the oral cytoskeleton. A zone with strongly argentophilic kinetosomes. which we have denominated Villeneuve-Brachon's fields, is located on the right side of the vestibular cavity. This zone is formed by kinetosomes strongly argentophilic, closely placcd, with normal cilia and long roots that penetrate into the endoplasm. The vestibular cavity possesses two ciliated margins formed by the anterior extremes of the somatic kineties. The right margin is constituted exclusively by these kinetics, while the left margin possesses numerous supernumerary kinetics. These two margins retain the ectoplasmic fibrillar derivates of the somatic cortex, but their fine structure is different. The dorsal cytoskeleton of the vestibular cavity is made up of two microtubular systems, and the ventral side is reinforced by thick periodical fibers. Our observations confirm the systematic position of the genus Balantidium within the order Vestibulilerida of the subclass Trichostomatia. © 1992, Gustav Fischer Verlag Jena. All rights reserved.