Life cycle ofSarcocystis gongyli Trinci 1911 in the skinkChalcides ocellatus ocellatus and the snakeSpalerosophis diadema

Abstract

The life cycle ofSarcocystis gongyli was established and its stages were studied by means of light and electron microscopy. The life cycle of this parasite needs two hosts, the skinkChalcides ocellatus ocellatus as the intermediate host and the snakeSpalerosophis diadema as the final host. Microscopically visible sarcocysts were observed in the skeletal muscles of naturally infected skinks (infection rate, 63%). These cysts measured 60–100×200–900 μm (mean, 85×600 μm). Typical mature cysts were bordered by a primary cyst wall folded into long, leaf-like protrusions, which reached approximately 2.4 μm in length and were never branched. The interior of the cyst contained both metrocytes and cyst merozoites that showed the typical characteristics of the Apicomplexa. Experimental transmissions of the parasite from naturally infected intermediate hosts (skinks) to final (definitive) hosts were carried out. Only the snakeSp. diadema (family Colubridae) shed fully sporulated oocysts of theIsospora type (each with two sporocysts). The prepatent period was 14 days and the patent period ended 60 days post-infection (p.i.). Gamogony and sporogony were found within the intestinal epithelial cells of the snake. Free sporocysts in fresh snake feces measured 9.1×10.6 μm on average. The fine structure of the gamogonic and sporogonic stages was studied. Gamogony occurred within the first 8 days p.i., giving rise to young oocysts in the epithelial cells of the small intestine.