Publication Date

1-1-1998

Document Type

Dissertation/Thesis

First Advisor

Ende, Carl von

Degree Name

B.S. (Bachelor of Science)

Department

Department of Biological Sciences

Abstract

The purpose of this project was to evaluate the effect of predator group size on per capita ingestion rates of the flatworm Dugesia tigrina, and to determine whether an optimum group size exists. In previous experiements performes by Cash et al. (1993,1995), it was determined that when Dugesia was fed Daphnia and mosquito larvae, per capita ingestion rates were higher in predator groups of four and eight. My project was designed to determine if the same pattern would be found if the flatworms were given isopods (Caecidotea sp.,) to prey upon, which are benthic organisms. To accomplish this, flatworms were maintained in groups of one, two , four, eight, ten, and sixteen, and were fed a constant ratio of three isopods per predator. Each experiment was run for five days, counting and replacing eaten prey daily. A total of six experiments were performed, three of which included a mesh screening in the bottom of the dishes. Per capita ingestion rates were determined and analyzed. The results showed no significant difference in per capita ingestion rates between group sizes. However, there was a significant overall decrease in per capita rates among the flatworms in the dishes containing screen compared to those without the screen. It is hypothesized that the screen enabled the isopods to more easily escape predation by the flatworms. It is thought that, in addition to a food source, this may be one reason that isopods in natural environments are found on the undersides of dead leaves and vegetation.

Comments

Includes bibliographical references.

Extent

14 unnumbered pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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