Further observations on the sporogony of Eimeria sardinae in the testis of the herring Clupea harengus L.

Abstract

Sporocyst formation commences with division of the sporoblast nucleus, after which two sporozoites develop, one at each end of the sporoblast. A thickening beneath the limiting unit membrane of the sporoblast is the first indication of the sporozoite pellicle forming. This subsequently develops into a cone-shaped structure, which becomes the anterior end of the sporozoite as it separates from the sporocyst residuum. The sporozoites elongate as they mature, and the sporocyst residuum, containing amylopectin and refractile granules, becomes smaller. A typical apical complex is present at the blunt anterior end of the sporozoite. A homogeneous area containing paracrystals is present in both the sporoblast and the sporozoite. There are no refractile granules in the sporozoite. The sporocyst wall is thin and contains no mechanism for releasing the sporozoite, such as a Stieda body or suture.