Ultrastructural studies of the zygote and oocyst wall formation of Eimeria truncata of the lesser snow goose.

Zygote development and oocyst wall formation of Eimeria truncata occurred in epithelial cells in renal tubules and ducts of experimentally infected lesser snow geese (Anser c. caerulescens). Post-fertilization stages were present throughout the kidneys beginning nine days post-inoculation. Initially, a single plasmalemma enclosed the zygote, and type 1 wall-forming bodies (WF1) became labyrinthine and moved toward the surface. There, WF1 degranulated and formed the outer layer of the oocyst wall between the plasmalemma and a newly formed second subpellicular membrane. Several WF2 fused and formed the inner layer of the oocyst wall between the third and fourth subpellicular membranes. Six subpellicular membranes were observed during wall formation. Other features of oocyst development were similar to those of other eimerian species.