Date of Award:

5-1-1980

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Nabil N. Youssef

Committee

Nabil N. Youssef

Committee

Gary L. Kelley

Committee

Paul B. Carter

Committee

LeGrande C. Ellis

Committee

James L. Shupe

Abstract

Although life cycles of many coccidian parasites are well documented, the exact sequence of events involved in the process vii of micro- and macrogamete encounter and subsequent zygote formation have remained poorly understood. The purpose of this investigation was to characterize the fertilization process of Eimeria tenella. Excysted sporozoites of Eimeria tenella were inoculated into Leighton tube cultures of primary chicken kidney cells and allowed to develop through oocyst formation. Additionally, sporulated oocysts of E. tenella were administered to young coccidia-free chickens. Infected cell cultures and cecal epithelium were processed for electron microscopy. Observations were also made on living infected cell cultures and data recorded and analyzed cinematographically. Successful gamete union in E. tenella was facilitated by the formation of foci of schizont and, later, gamont development as a function of early generation distributional patterns. Such developmental foci probably represent a natural selection for the most vigorous early generation infective stages to develop in suitable host cells. Microgamete migration was accomplished both inter- and intracellularly in cell cultures via flagellar contact resulting in a pushing-off action. Microgametes were also found in the lumen of infected chicken cecum. Macrogamonts and macrogametes were observed both within host cells and in the lumen of infected cecal epithelium or free in cell culture medium. Analysis of living and fixed tissues indicated that contact between gametes was initiated as a result of the motile activity of microgametes, primarily manifested as adherence of flagella to macrogamete surfaces. Incorporation of microgametes into the cytoplasm of macrogametes occurred in a manner similar to that described for mammalian gamete union; the microgamete in a parallel position with respect to the macrogamete surface. Sequential stages in microgamete incorporation as well as the presence of an entire microgamete in macrogamete cytoplasm was recorded. Oocyst wall formation appeared to be initiated by physical contact between gametes and not necessarily total penetration and fertilization. Oocyst walls may form even in infertile macrogametes but probably represent a portion of the oocyst population that does not sporulate.

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