Fine structure of an amoeba of the genus Vahlkampfia (Rhizopoda, Vahlkampfiidae), a parasite of the gut epithelium of the bristletail Promesomachilis hispanica (Microcoryphia, Machilidae)

Abstract

The ultrastructural cytology of a cyst-forming amoeba of the genus Vahlkampfia is described. It was present in the midgut epithelium of the bristletail Promesomachilis hispanica, collected in Spain. All stages are uninucleate, having vesicular nuclei. The irregular, up to 11.9 μm long, trophozoites develop near the basal lamina. Cysts are released into the gut lumen. Trophozoites have a simple plasma membrane, devoid of surface ornamentations. Golgi apparatuses consist of loosely aggregated vesicles. Mitochondria of trophozoites and cysts are closely associated with ribosomes and the rough endoplasmic reticulum. Mature cysts are spherical to oval, measuring up to 10.9 μm in diameter. The up to 1.1-μm-thick cyst wall is multilayered, with a wide, fibrous zone and a surface layer resembling a ca. 5-nm-thick unit membrane. The reasons for including the amoeba in a genus of the class heterolobosea are discussed, and the organism is compared to other insect pathogenic amoebae.