Electron microscope studies of macrogametes and fertilization in Eimeria bovis.

Abstract

Mature macrogametes of Eimeria bovis in the mucosa of the colon of calves killed 17 days after inoculation had a characteristic fine structure. Numerous osmiophilic wall-forming bodies of type I were located peripherally in the macrogamete, whereas the wall-forming bodies of type II were relatively large and located more centrally. Numerous polysaccharide bodies and lipid inclusions were also present. The parasitophorous vacuole, when present, was narrow and had electron-pale contents. The host cell cytoplasm was vacuolated; in some specimens the host cell appeared to have disintegrated. A microgamete was observed within a vacuole in the cytoplasm of a macrogamete from a calf killed 19 days after inoculation. This microgamete had two flagella and a homogeneous osmiophilic nucleus. The wall-forming bodies of type I and type II were altered in this macrogamete as compared with those of mature macrogametes, indicating that oocyst wall formation had begun. Many microgametes were observed in the cytoplasm of the host cell as well as in the parasitophorous vacuole of the macrogamete.