Date of Award

2019

Degree Name

Biological Sciences

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Brian Antonsen, Committee Chairperson

Second Advisor

Dr. David Mallory

Third Advisor

Dr. Herman Mays

Fourth Advisor

Dr. NadjaSpitzer

Abstract

Manganese is a prominent heavy metal within the earth’s crust and a micro mineral essential for biological function, however, high level exposure may lead to neurological defects. Industrial activities allow elevated manganese (Mn2+)to enter air and waterways. The Environmental Protection Agency (EPA) implements secondary standards for aesthetics in drinking water at 0.05 ppm Mn2+, although evidence indicates levels at, or below this concentration negatively impact aquatic life. Crayfish (Procambarus clarkii) were exposed to environmentally relevant Mn2+ concentrations for 6 months, while the control group was kept in reconstituted fresh water for the same time period. During this time, crayfish were placed in a novel environment weekly and videotaped for 20 minutes. Control crayfish continually increased time and distance moved throughout the 6 months while remaining mostly in border regions, but freely exploring the novel environment. Animals treated with lower Mn2+ concentrations moved lesser time and distances, while darting between zones. The highest concentration Mn2+treatment continually moved elevated time and distances while remaining concealed within the border throughout the experiment.When threat-avoidance behaviors were analyzed over the weeks, control crayfish continually increased stopping behavior and reduced escape behavior. Mn2+ treated crayfish displayed suppressed tail-flip frequencies indicating neurological impact; however, in later weeks, they increased tail-flip and startle response frequencies compared with the control group. Based upon my data, I suggest manganese exposure at levels below EPA standards may lead to physiological stress and behavioral differences which may impact crayfish survivability.

Subject(s)

Crayfish -- Behavior.

Crayfish -- Ecology.

Crayfish culture -- Ecology.

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