Ultrastructural Observations on Secondary Merogony and Gametogony of Dactylosoma ranarum Labbe, 1894 (Eucoccidiida; Apicomplexa)

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Abstract
Ultrastructural observations on secondary merogony and gametogony of Dactylosoma ranarum (Lankester, 1871) Labbe, 1894, in erythrocytes of Rana esculenta were made on standard thin sections and freeze-fracture replicas. Secondary merozoites formed by peripheral budding with karyokinesis and cytokinesis occurring simultaneously during early merogony. Secondary merozoites had a trilaminate pellicle, micropores, a conoid with 2 apical rings, 4 rhoptries, and numerous micronemes. Amylopectin inclusions were observed occasionally within secondary merogonic and gametogonic stages. Gamonts of D. ranarum were recurved within the host erythrocyte and were folded posterior to their nucleus to produce a "tail" which was approximately one-half the diameter of the prenuclear region and which extended back about 80% of the length of their anterior portion. Each gamont had a complete apical complex including a conoid. Approximately 50 subpellicular microtubules were located in the anterior region; none occurred in the posterior portion. Male and female gamonts could not be distinguished by either light or electron microscopy. The membrane of the parasitophorous vacuole surrounding immature gamonts was elaborated into a network of membranous extensions projecting into the neighbouring erythrocyte cytoplasm. Freeze-fracture replicas of such extensions demonstrated that the network is contiguous with the membrane of the parasitophorous vacuole surrounding immature gamonts and that it may be related to the entrance of these stages into the erythrocyte.