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Brent B. Nickol

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Date of this Version



Thesis (M.S.)--University of Nebraska-Lincoln, December 1987.

Presented to the Faculty of the Graduate College in the University of nebraska in partial fulfillment of requirements for the degree of Master of Science.

Major: Biological Sciences.

Under the supervision of Professor Brent B. Nickol.


Copyright 1987, W. Scott Monks. Used by permission.


The mechanism by which Moniliformis moniliformis might regulate the population size of its host was studied. Theoretical models of intensity-dependent population regulation of hosts by parasites require that as the relative density of parsites within the population of hosts is increased the degree of aggregation of parasites must increase. This relationship was studied in "free-ranging" laboratory rats presented with cockroaches. Changes in the relative density, ratio of the variance to the parameter k of the negative binomial distribution were evaluated as indicators of changes in aggregation.

A significant difference in the degree of aggregation between males and females was found at both treatment levels. A significant increase in aggregation of parasites due to the increase in density of infective stages in the intermediate host occurred in female rats but not in male rats. A significant increase in the degree of aggregation of parasites occurred as a result of the increase in relative density of infective stages available to the rats as required by the model. The best indicators of the degree of aggregation was found to be the ratio of the variance to the relative density and the ratio of the log-variance to log-relative density. Changes in k were not correlated with changes in over-dispersion or the relative density.