Ultrastructural studies on oocysts, sporulation and sporozoites of Schellackia cf. agamae from the intestine of the starred lizard Agama stellio

Abstract

Young intracellular oocysts of Schellackia cf. agamae in the gut epithelium of Agama stellio were bound by several fine membranes. Later-stage oocysts and sporoblasts in the lamina propria were intercellular and were bound by a thin but firm tri-layered wall. Oocysts had a large central refractile body which, during sporulation, sent extensions into the developing sporozoites. Sporozoites escaped into the gut tissue, leaving a large oocyst residuum with the remains of a refractile body. These sporozoites invaded a variety of connective tissue cells, endothelial cells and circulatory leucocytes in the lamina propria. Sporozoites caused lysis of the host cell cytoplasm at their perimeter and multiple sporozoite infections led to complete degradation of the host cell.