Electron Microscopy of the Bacillary Band and Stichosome of Trichuris muris and T. vulpis

Abstract

The bacillary band is composed of tall columnar cells. The basal plasma membrane is folded and interdigitates with adjacent cells. The cytoplasm is filled with RNP particles and a fine endoplasmic reticulum. The apical area contains numerous mitochondria and a complex system of lamellae formed by invaginations of the plasma membrane. A homogeneous secretory mass fills the cuticular pore. The stichosome consists of a row of cells each of which partially or completely encloses the esophagus. The entire stichosome and esophagus are enclosed by a membranous sheath consisting of many fine layers. The central nucleus has many fine blebs arising from its surface. Numerous electron-dense granules are scattered in the cytoplasm. Large vesicles with connecting canaliculi occur throughout the cell. The esophageal lumen is enclosed by tubular cells. The fine structure suggests that the stichocytes may be secretory in function but no evidence of a secretion leaving the cell has been observed. The bacillary band also appears to secrete a substance through the cuticular pores but the nature of this product is undetermined. Comparison of the fine structure of the Malpighian tubules of insects and mammalian kidney tubule cells with that of the bacillary cells suggests an excretory function. The stichosome and bacillary band of the anterior portion of the members of the superfamily Trichuroidea have been studied by many investigators. Eberth (1859) reported many rodlike shafts in the bacillary band and described the esophagus as being embedded in a row of large cells termed the Zellenkorper. Bastian (1866) interpreted the bacillary band as an area of cuticular pores. He considered the granular cells of the stichosome to have replaced the usual esophageal muscle fibers. Rauther (1918), in a detailed study, described the bacillary band and noted the presence of a secretory product. He also reported intracellular canals opening into the esophagus in the cells of the stichosome. Jagerskiold (1901) studied the bacillary Received for publication 10 May 1963. * From a dissertation submitted in partial fulfillment of the requirements of the degree of Doctor of Philosophy at Louisiana State University. This work was supported in part by U.S.P.H.S. Grant E-2347. t Present address: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland. bands of several nematodes and concluded that the bacillary band consisted of many hypodermal glands, each having a cuticular pore. Since these nematodes lack the usual excretory system Jagerskiold thought that the hypodermal glands were excretory in function. Miller (1929) reported that the bacillary band was important in the feeding of the worm. He believed the esophagus to be nonfunctional since muscle fibers were not observed. The bacillary band and the stichosome were related in nutrition while the intestine served as an excretory organ. Chitwood (1930, 1935) rejected Miiller's theory and reported the presence of muscle fibers in the esophageal wall. He also noted that each stichocyte had an opening into the esophageal lumen and thus confirmed the opinion that the stichocytes were esophageal glands. A comparison of electron microscopic studies with previous light microscopy investigations should clarify and expand present knowledge of the structure of the bacillary cells and stichocytes of the genus Trichuris, and give insight into the relationship of form to function in these nematodes.