Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School


First Advisor

E. J. Hugghins


A Sarcocystis species found in the wapiti (American elk) of South Dakota was macroscopically, microscopically, and ultrastructurally examined. Macroscopic and microscopic examination provided typical features of a sarcocyst, whereas ultrastructural examination revealed unique features in the primary cyst wall and a quadripartite arrangement of organelles in the merozoite. The sarcocysts observed were shiny white elongated ellipsoids embedded in what appeared to be an intramuscular vacuole. The primary cyst wall consisted of densely packed palisade-like protrusions (villi) and a wide underlying ground substance. Distinctive features of the palisade-like villi included peripherally supportive microfibrils which did not extend into the underlying ground substance, invaginations in the unit membrane along the entire villi surfaces, and concentrations of invaginations between the basal regions. The quadripartite arrangement of organelles in the merozoite is different from any previously described species. The anterior, central, and posterior regions of the merozoite contained the apical complex, mitochondria/golgi bodies, and nucleus, respectively. The fourth region, consisting of peripherally concentrated micronemes and amylopectin granules, encapsulated the three former regions. The organelles of the fourth region are ordinarily incorporated into the three-region merozoite. The quadripartite arrangement· of organelles may be significant to their affiliated functions. The value of the ultrastructurally unique features found in this Sarcocystis species, as a criterion of nomenclature, is dependent upon the identification of the definitive host and completion of the parasite's life cycle. To assume that the observed sarcocysts are the only possible species infective to wapiti would be presumptuous at this time.

Library of Congress Subject Headings

Ultrastructure (Biology)
Protozoa, Pathogenic
Elk -- Diseases -- South Dakota



Number of Pages



South Dakota State University