Ultrastructure of the cyst wall and merozoites ofSarcocystis from moose (Alces alces) in Alberta, Canada

Abstract

Two distinct types of cysts of Sarcocystis from the musculature of moose (Alces alces) were compared by electron microscopy. The fusiform Type A cysts differed from the spherical Type B cysts in the appearance and thickness of the primary cyst wall, organization of cyst interior, and the presence of a secondary cyst wall around Type B. The respective merozoites also differed in size as well as in the number of rhoptries and diameter and arrangement of micronemes. Comparison of the ultrastructure of the moose sarcocysts with those described from other ungulates revealed substantial differences. It appears that two hitherto undescribed species of Sarcocystis are present in moose although cross-transmission and additional life cycle studies are necessary for a complete description.

Ultrastructure of the cysts of Sarcocystis rangi from skeletal muscle of reindeer (Rangifer tarandus tarandus)

“…From Colwell and Mahrt's description of these «extensions* one gains the impression that they are very thin structures, which led me to believe that they had a certain structural resemblance to the thin, striplike surface processes of S. grueneri (Gjerde 1985a(Gjerde , 1985b). However, a closer examination of the micrographs presented in the paper by Colwell and Mahrt (1981), reveals that these cysts actually have hairlike surface processes with diameters of up to about 0.4 um, and a length of at least 5.8 Um.…”

“…It therefore seems as if only the electron-dense membraneous boundaries (reinforced cyst membrane), and not the electron-lucent central core of the projections, have been recognized as extensions from the cyst, and described as membraneous extensions by Colwell and Mahrt (1981). Thus, S. alceslatrans also resemble S. rangi in cyst surface morphology.…”

Sarcocystis in moose (Alces alces): molecular identification and phylogeny of six Sarcocystis species in moose, and a morphological description of three new species

“…Colwell and Mahrt (1983) complemented the species description and assigned the name S. alceslatrans to the type A cysts that they previously had described grossly and by TEM (Colwell and Mahrt 1981). Transmission electron micrographs presented in their paper from 1981 reveal that these cysts have hairlike protrusions running along the surface of the cysts, similar to those of S. rangi of reindeer (Gjerde 1985d), Sarcocystis sybillensis of elk/wapiti (Dubey et al 1983) and…”

“…Mahrt and Colwell (1980) screened muscular tissues from 205 Canadian moose for Sarcocystis infection, and reported a prevalence of 96%. Colwell and Mahrt (1981) examined the oesophagus, tongue and diaphragm of moose from Alberta, Canada, and described two types of cysts, based on gross examination and TEM. Type A cysts were fusiform, 1.0-7.0 mm×0.5-0.7 mm, whereas type B cysts were nearly spherical and 0.5-2.0 mm in diameter.…”

“…Type II was ribbon-shaped, with short finger-or palisade-like protrusions. Kutkienė concluded that the type I cysts corresponded to S. alceslatrans, as described by Dubey (1980) and to the type A cysts as described by Colwell and Mahrt (1981).…”