Fine structure of the intestine of the nematodes, Ancylostoma caninum and Phocanema decipiens

The monolayered, intestinal epithelium of the ascaroid, Phocanema decipiens is composed of an innumerable number of uninuclear cuboidal to columnar cells. In the strongyloid, Ancylostoma caninum only the anterior and posterior parts of the intestine are cellular, and are composed of only two longitudinal rows of polynuclear cells, whereas cell boundaries are not found in the middle part of the intestine, i. e. the epithelium is a syncytium. This latter fact is here demonstrated for the first time by electron microscopy in the intestine of nematodes. The basal plasma membrane covering the intestine of both nematodes has invaginations, and towards the perienteric cavity a basal lamella is present. Towards the intestinal lumen the epithelium is covered with microvilli. The central cores of the microvilli as well as the terminal web, with which the cores are connected, appear homogeneous in the strongyloid but are composed of filaments in the ascaroid. In A. caninum, the epithelium is characterized by the presence of mitochondria and rough-surfaced endoplasmic reticulum, the latter often in characteristic whorl-like arrangements. A Golgi complex, various lysosome-like bodies and pigment granules are also present. In P. decipiens the intestinal cells are filled with deposits of glycogen, lipid droplets and lipo-protein granules. The mitochondria are characteristically concentrated in the apical part of the cells and along the cell boundaries. It is pointed out that the structures of the intestinal cells are in accordance with the feeding biology of the nematodes.