Ultrastructure of a Sarcocystis sp. infecting skinks of the genus Agama

Abstract

Macroscopically visible sarcocysts were observed in the skeletal muscles of naturally infected skinks of the genus Agama (infection rate 11.3%). Sarcocysts were described by means of transmission electron microscopy. These cysts measured 0.03–0.25 × 0.38–1.7 mm (mean 0.12 × 1.1 mm). Typical mature cysts were bordered by a primary cyst wall that measured 2.4–5.3 μm (mean 3.9 μm) and was folded into a few nonbranched finger-like protrusions measuring 0.7–1.5 × 1.0–2.5 μm (mean 1.2 × 1.5 μm). These protrusions contained granular elements, but filaments and tubular elements were not observed. A relatively thick, homogeneous tape was observed just underneath the primary cyst wall, measuring 0.5–1.0 μm (mean 0.8 μm) and containing a granulated ground substance in which filaments and tubular elements were not observed. Metrocytes measured 3.1–5.5 × 4.2–7.2 μm (mean 4.0 × 5.8 μm) and merozoites measured 1.2–3.3 × 4.4–8.6 μm (mean 2.6 × 7.5 μm). The fine ultrastructural characteristics of both metrocytes and merozoites were similar to those described for many Sarcocystis species and were generally nonspecific.