SARCOCYSTIS, TOXOPLASMA AND RELATED PROTOZOA 



319 



parasite or the host. A few authors, such 

 as Wang (1950), think that the host forms 

 both layers, but this view is probably not 

 correct. Some, such as Chatton and Avel 

 (1923) and Barretto (1940), think that the 

 parasite forms both layers. Others, such 

 as Scott (1943), think that the parasite 

 forms the inner layer and the host the 

 outer; still others, such as Babudieri 

 (1932), think that the whole cyst wall is 

 formed by the parasite in S. ))uiris and 

 similar species, and that one layer is 

 formed by the parasite and the other by 

 the host in S. teiiella and similar species. 



According to Ludvik (1960), the single- 

 layered cyst wall of S. iiiiesclieriana is 

 quite certainly formed by the parasite, and 

 the villi which project into the muscle tissue 

 take up nutritive material from the host. 



The trophozoites are banana-shaped 

 when mature, with the anterior end 

 slightly pointed and the posterior end 

 rounded. They are 6 to 15|i long and 2 

 to 4/i wide, varying in size with the spe- 

 cies. They move by gliding or body 

 flexion, twisting, turning, or following a 

 spiral path. 



SARCONEMES 

 DISCOID GRANULE 



CENTRAL 

 GRANULES 



POLAR RING 

 TOXONEME 



PELLICULAR 

 FIBRILS 



MITOCHONDRION 



POLAR RING 



SARCONEMES 



NUCLEUS 



MITOCHONDRION 



TROPHOZOITE OF SARCOCYSTIS TENELLA 



Fig. 36. Trophozoite oi Sarcucyslti tciiella. (After Ludvik, 1958) 



Ludvik (1958, 1960) described their 

 structure in S. lenella and S. niiescher- 

 iaiia on the basis of electron microscope, 

 cytochemical and light microscope studies. 

 At the anterior end within the pellicle is a 

 polar ring 0.4 to 0. 5j_i in diameter, and 

 within it is a hollow, truncate cone 0. 3 to 

 0.4|i long known as a conoid. From the 

 polar ring 22 to 26 fine fibrils run back- 

 wards in the pellicle the full length of the 

 body. In some individuals short, club- 

 shaped structures similar to the toxo- 

 nemes of Toxoplasma can be seen in the 

 cytoplasm beneath the pellicle. 



The cell body is divisible into 3 zones. 

 The anterior third of the body, the so- 

 called fibrillar zone, is filled with a large 



number (about 300 to 350) of parallel, 

 equidistant fibrils or perhaps channels 

 about 50 nijLt in diameter, the sarconemes. 

 They probably arise from the conoid, and 

 they end abruptly. Just under the pellicle 

 on the dorsal (convex) side about the mid- 

 dle of the fibrillar zone is a disc-shaped 

 granule which stains with Bodian silver. 



The middle third of the body contains 

 a large number of spherical granules 0.4 

 to 0. 5fi in diameter, the so-called central 

 granules. They impregnate with osmium 

 and stain intensely with Heidenhain's hema- 

 toxylin but not with Giemsa. In the same 

 region are many minute granules, some of 

 which contain volutin and others RNA. 

 There are also 1 or 2 large vacuoles which 

 stain with neutral red. 



