Eimeria tenella: further studies on the development of the oocyst

The present study investigated the processes of macrogametogenesis and oocyst formation of Eimeria tenella (Xiamen strain), including the formation of wall-forming body1 (WFB1) and wall-forming body 2 (WFB2), the club-shape body and the origin of the residual body during the transformation from a macrogamete to an oocyst.

Transmission electron microscopy was used to follow ultrastructural changes of the organelles during parasite development. Frozen section techniques and special staining were used to determine the chemical composition of the club-shape body.

Electron lighter WFB1 appeared earlier than the electron denser WFB2 during the process of cyst wall formation. WFB2 appeared to play a key role in cyst wall formation, whereas WFB1 may have a limited role in the wall-forming process. When two last generation merozoites entered the same host cell simultaneously, one of them grew well, but the other one was developmentally retarded, and became a residual body. Our study indicates that the content of the club-shape body are lipoidal in nature, not amyolpectin as suggested previously, because they stained black by Sudan black-B.

During of macrogametogenesis and oocyst formation of E. tenella (Xiamen strain), WFB2 plays a major role in cyst wall formation. The residual bodies come from the undeveloped macrogametes. The club-body is lipoid; and lipometabolism is important energy resource in E. tenella development.