Light microscopical observations on sporogony of Sarcocystis rauschorum (Protozoa: Sarcocystidae) in snowy owls (Nyctea scandiaca)

Abstract

The purpose of the study was to describe, by light microscopy, sporogony of Sarcocystis rauschorum (Protozoa: Sarcocystidae). Two coccidia-free snowy owls (Nyctea scandiaca) were fed bradyzoites of S. rauschorum from varying lemmings (Dicrostonyx richardsoni). At necropsy, 7 days postfeeding, numerous owl tissues were fixed in 10% neutral buffered Formalin and processed for histological examination. Zygotes, oocysts in various stages of sporulation, and fully sporulated oocysts were observed only in the lamina propria of the small intestine. Sporogony of S. rauschorum is similar to that of some other species of Sarcocystis: first nuclear division to two polar nuclei in the oocyst, then cytokinesis with a second nuclear division resulting in two sporoblasts each with two polar nuclei, and finally a third nuclear division and cytoplasmic development producing two sporocysts each with four sporozoites.