Francine M. G. McCarthy

B. Sc. Honours Thesis

Infraspecific Variation in Arcellacea (Thecamoebians) from Eastern Canada and a Selected Biostratigraphic Study

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Clones of several morphotypes of the arcellacean species Centropyxis aculeata (Ehrenberg) were established and the range of variation in individual clones was examined. Considerable morphological variation was noted, particularly in apertural shape, test shape and degree of agglutination. This has important implications for the taxonomy of arcellaceans, indicating that delimiting species on the basis of one, or a few, genetically simple morphological differences is unsound.

The second part of this study consists of the determination of arcellacean species assemblages in a core taken from Robinson's Lake, Newfoundland. The lower part of the core contains marine microfossils, and is followed by a brackish freshwater transition zone dominated by Centropyxis aculeata. The freshwater zone is dominated by Difflugia oblonga or co-dominated by Difflugia oblonga and Pontigulasia compressa. The assemblage zones allowed a paleoecological interpretation of this part of Newfoundland to be made particularly with respect to sea-level changes, and this study is a further indication of the value of arcellaceans as tools in paleoecological studies.

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Pages: 50
Supervisor:  Franco Medioli / David Scott