Date of Award

Winter 2007

Project Type

Thesis

Program or Major

Zoology

Degree Name

Master of Science

First Advisor

James F Haney

Abstract

Changes in the filter appendage surface area (FSA) of Daphnia in response to cyanobacteria were examined in an effort to learn more about the relationship between Daphnia and extracellular cues exuded by cyanobacteria. The filtering appendage areas of two strains of D. pulex were measured after feeding on high and low concentrations of a mixture of Nanochloropsis spp. and toxic Microcystis aeruginosa for one generation. Daphnia were also raised in a filtrate of this same M. aeruginosa and given high and low concentrations of food to determine the cause of increased FSA in the presence of cyanobacteria: low amounts of nutritious phytoplankton or response to chemical cues produced by the cyanobacteria. I observed an increased FSA in response to increased proportions of M. aeruginosa . However, there was no change in FSA as the amount of M. aeruginosa filtrate increased and food levels remained constant, thus suggesting that the lack of nutritious food is the most proximate cause of increased FSA.

Patterns consistent with laboratory experiments were observed in Daphnia from eight lakes of varying trophic status. The Daphnia from the most oligotrophic lakes had the largest FSA and Daphnia from eutrophic systems with an abundance of cyanobacteria had a greater FSA than more mesotrophic systems.

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