Ultrastructure of the sporozoite and the sporocyst wall of the coccidian species Adelina triboliiBhatia, 1937 within the course of an autoinfection

Abstract

Summary A description is given of the ultrastructure of the oocyst, the sporocyst and the sporozoite of the coccidian species Adelina tribolii, and of the development of the sporozoite in the original host, Tribolium castaneum (autoinfection). There are generally eight spherical sporocysts (10–13 μm in diameter) in the mature occyst. If the infection is heavy, the fat body of the host contains frequently broken and empty sporocysts. The wall of the sporocyst has three layers which change in their morphological appearace (undulation) after the rupture of the wall in its four, plate-like sutures. The wall of the sporocyst curls along its margins, and the sporocyst is invaded by the host cytoplasm and its nuclei. The sporozoite has two large, paranuclear bodies of a characteristic, crystalline structure which are surrounded by a layer of amylopectin-like granules. Sporozoites that have a conoidal complex are surrounded by a three-layered, cytoplasmic membrane. The sporozoite settles in the tissue and develops there in a trophozoite. The surface of the wall of its parasitophorous vacuole is extremely rough. As the trophozoite ages, the number of amylopectin-like granules increases, and that of micronemes decreases. The most persistent of the conoidal complex is its apical ring. Both the nucleus and the nucleolus of the trophozoite increase in size. The trophozoite changes in a schizont, its nucleus undergoes several divisions. The cortical layers of its cytoplasm have numerous, amylopectin-like granules.