Dr. Murai Éva szerk.: Parasitologia Hungarica 23. (Budapest, 1990)

RESULTS Sarcocysts were found in the tongue, pharynx, oesophagus, diaphragm and intercostal muscle of five adult and two juvenile deer which gives an infection rate of 85 %. The cysts were macroscopically visible and measured 1-4 mm in length and 0.1-0.5 mm in width according to macrophotographs taken of cysts in the oesophagus. Some of the sarcocysts were of considerable age as evidenced by the empty compartments in the center of the cyst (Fig. 1). Ultrastructurally, each sarcocyst was limited by a unit membrane, the primary cyst wall, with a thin underlying electron-dense layer. The wall had regularly spaced projections that arose from the base on a pedestal-like stalk. At the distal end the projections flared out laterally and had a flattened surface (Fig. 2). The projections were relatively uniform in size, measuring 0.2-0.35 itm in height (N=10) and 0.4 /xm - 0.5 jam in width. They were separated from each other by a distance of approximately 1.3-1.6 jxva. The intervening area on the surface of the wall between the projection was covered with closely spaced undulations which measured 50-55 nm in height (N=10) (Figs. 2,3). A finely granular, relatively thin, electron- pale ground substance, 1.0-2.0 jxm in thickness, surrounded the cyst and separated the sarcoplasm from the parasite (Fig. 2). The ground substance extended distally into the projections, and internally as septa that divided the cyst into compartments which contained tightly packed bradyzoites (Figs. 1,2). The cyst merozoites had ultrastructural features typical of these stages, such as a pellicle of 3 membranes, conoid, micronemes, rhoptries, dense granules and amylopectin inclusions (reviewed by CHOBOTAR and SCHOLTYSECK 1982). They measured 10.8 x 2.4 /xm (8.6-11.5 x 2.1-2.6; N= 10). DISCUSSION The ultrastructural study of cyst wall construction has become an established method of distinguishing between species of Sarcocystis in a given host (MEHLHORN et al. 1976, MEHLHORN and HEYDORN 1978, DUBEY and SPEER 1985, DUBEY et al. 1989). Thickness of the wall and shape, arrangement and size of surface projections are consistent features of mature sarcocysts. The cysts observed in Siberian roe deer in the present study were "thin-walled" (less than 2 /xm) since they lacked the prominent projections that produce spiny or striated "thick-walled" cysts found in numerous species (MEHLHORN et al. 1976, ENTZEROTH 1982, DUBEY et al. 1989). Structurally these cysts closely resembled sarcocysts described from roe deer (Capreolus capreolus) designated as type 5 in an earlier study (ENTZEROTH 1982). The size and arrangement of the projections and the thickness of the ground substance are nearly identical. In a recent major treatment of Sarcocystis by DUBEY et al. (1989), the sarcocysts from ENTZEROTH's (1982) study were designated as S. sibirica, a name proposed by MATCHULSKI in 1947. In the original work recently translated into English (courtesy of Dr. Tamara BEYER, Institute of Cytology, Leningrad) MATCHULSKI (1947) stated that "sarcosporidian sacks were observed along the whole length of the esophagus". The sacks were macroscopic, "0.9-1.6 mm in length