Date Approved


Graduate Degree Type


Degree Name

Biomedical Sciences (M.H.S.)

Degree Program

Biomedical Sciences

First Advisor

Dr. Daniel Bergman

Academic Year



Current research suggests that stress in both vertebrates and invertebrates is modulated in part by the neurotransmitter serotonin. It has been shown that crayfish can function as a good neurophysiological model, as they have less complex neurological systems than vertebrates, so mechanistic causes for stress can be more readily studied and understood. One potential stressor for aquatic species such as crayfish would be nonylphenol, a hydrophobic chemical used in agricultural products that can make its way into the water supply due to agricultural runoff. Nonylphenol can lead to physiological and behavioral impairments in crayfish and these impairments likely induce stress in crayfish. Long-term exposure to nonylphenol may therefore induce a chronic stress response in crayfish. One potential target for the treatment of stress is serotonin. Previous research demonstrating that serotonin will increase stress in crayfish has been performed but was conducted using acute stressors, therefore lacking the effects of serotonin on the chronic stress response. Many have also performed behavioral analyses to determine anxiety rather than quantifying stress. Therefore, studies specifically looking at chronic stress may be necessary to give a more in-depth description of the stress response after treatment with serotonin to further the knowledge base on the effects of serotonin on the stress response in crayfish. To determine the relationship between chronic stress and serotonin, chronic stress will be induced via long-term nonylphenol exposure to crayfish, and then we will determine how these stress levels change after exposure to serotonin or a serotonin antagonist.