Date of Award:

5-1-1971

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Zoology

Committee Chair(s)

Datus M. Hammond

Committee

Datus M. Hammond

Committee

Hugh Stanley

Committee

Paul Carter

Committee

John Simmons

Committee

Thomas Bahler

Abstract

The occyst walls, sporocysts, excystation, and the development of first generation schizonts and merozoites of Eimeria callospermophili were studied. The different stages were fixed with Karnovsky's fixative or 5 percent glutaraldehyde and post-fixed with 2 percent osmium tetroxide or in 2. 5 percent glutaraldehyde and 2.5 percent osmium tetroxide together for electron miscoscopy. The oocyst wall had an outer layer consisting of columnar projections and an inner layer consisting of an outer band covered by a membrane and an electron-dense inner band. A membrane covered the sporocyst wall. Inside were 2 sporozoites, fluid which coagulated during fixation, and a membranebound residual body with vacuoles, lipoid granules and amylopectin. The Stieda body filled a gap in the sporocyst wall; just behind this was the homogeneous substiedal body. In sporocysts exposed to a mixutre of sodium taurocholate (bile salt) and trypsin, the Stieda body became less dense and the substiedal body began to evaginate. The Stieda body then disappeared and the substiedal body popped out and disintegrated, after which the sporozoites excysted. In sporocysts exposed to trypsin alone, excystation occurred less rapidly and at a lower percentage then when trypsin and bile salt were used; the substiedal body disintegrated in situ. Bile salt alone stimulated motility of the sporozoites in intact sporocysts, but no excystation occurred. Extracellular sporozoites had a pellicle with an outer unit membrane, inner membrane, and 24 subpellicular microtubules arranged in loose pairs. Unusual characters included two anterior polar rings, a posterior annulus, small amylopectin granules located around the periphery of the refractile bodies, and fibrillar organelles. Sporozoites appeared to cause an interruption in the host cell limiting membrane during penetration. By 10 hours after inoculation, the nuclei of the intracellular sporozoites had enlarged and each had a distinct nucleolus and nuclear pores. Ribosomes were found in the nucleolus and in the nucleoplasm. A Golgi apparatus was present and 2 centrioles were found adjacent to one side of the nucleus in some specimens. The mitochondria appeared swollen. The enlarged nucleus and nucleolus then elongated and underwent division. Centrioles were observed at the posterior and anterior ends and microtubules were seen extending through the nucleoplasm. The nuclear membrane remained intact during division. The mitochondria also appeared to divide during this time. By 12 hours, sporozoiteshaped schizonts with 5 to 12 nuclei were present. In stages immediately preceding merozoite formation, an intranuclear spindle apparatus with conical polar areas was observed near the outer margin of each nucleus. Two centrioles were observed near each pole in some specimens. Merozoite formation began internally, with anlagen of 2 merozoites developing near each nucleus. The inner membranes of the merozoites first appeared as 2 dense thickenings adjacent to the polar cones and centroiles; then subpellicular microtubules, anterior annuli, and conoid were formed. Later, rhoptries, Golgi apparatus, refractile bodies and mitochondria were incorporated. The schizont became ovoid as conoid, inner membrane, rhoptries, and micronemes of the former sporozoite gradually disappeared. The forming merozoites elongated and approached the limiting membrane of the schizont. They then began to grow outward and additional organelles, including a nucleus, were incorporated. The single surface membrane of the schizont became the outer membrane of the merozoite pellicle. Merozoites finally pinched off from the residual body. Development in cell cultures and host tissues were similar. No 3H-thymidine was incorporated into the merozoites during development. The development of this species is compared with that of related Sporozoa.

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .