Morphological studies on the muscle cysts of Sarcocystis dirumpens (Hoare 1933) Häfner and Matuschka 1984 in several host species revealing endopolygeny in metrocytes.

Muscle cysts from rodents (Mastomys natalensis, Mus musculus, Rattus norvegicus, Meriones unguiculatus, Phodopus sungorus) experimentally infected with Sarcocystis dirumpens were examined by light and electron microscopy. The corrugated primary wall showed a pattern of densely arranged invaginations surrounded by minute bleb-like evaginations. True protrusions were absent. The length of the blebs and the thickness of the primary wall varied insignificantly but not remarkable host-dependent morphological differences could be noticed between the cyst wall structures 60-418 days p.i. In the mature parts of the cysts merozoites and metrocytes showed typical apicomplexan features of fine structure and mode of multiplication (endodyogeny). In the tips of the cysts large metrocytes simultaneously formed more than two daughter cells (at least up to 12) by endopolygeny.