Electron microscopic study on sporocysts and sporozoites of parental strains and precocious lines of rabbit coccidia Eimeria intestinalis, E. media and E. magna

The fine structure of sporocysts and sporozoites of parent strains and precocious lines of rabbit coccidia Eimeria intestinalis, E. magna and E. media was studied. The parent strains and precocious lines differ only in the shape and size of refractile bodies (RB). In the sporocysts of precocious lines of E. magna and E. media, one extremely large RB was seen, either inside one of the sporozoites, or free in the sporocyst. In the oocysts of the precocious strain of E. intestinalis, two sporocysts resembled those of the precocious lines of E. magna and E. media, whereas the other two sporocysts did not harbour any RB. Sporozoites of all the precocious lines contained no, or very small, RB after in vitro excystation.