Date of Award

Spring 5-8-2021

Document Type

Honors Thesis



First Advisor

Jacob Kerby

Second Advisor

Jeff Wesner

Third Advisor

Cliff Summers


neonicotinoid, imidacloprid, amphibian, brain, contaminants

Subject Categories

Terrestrial and Aquatic Ecology


Neonicotinoids are widespread and commonly used to fight agricultural pests. Unfortunately, these neurotoxic insecticides commonly reach nearby wetlands due to tile drainage systems and agricultural runoff. Non-target organisms, such as amphibians, use wetlands as habitat and are likely exposed to elevated neonicotinoid levels. We collected Northern leopard frogs and water samples from control and tile wetlands to compare imidacloprid brain concentrations and subsequent changes in brain morphology. Additionally, a lab-based experiment was conducted to further analyze the ability of imidacloprid and its metabolite, imidacloprid-olefin, to cross the blood-brain barrier. Tile wetlands had higher aquatic imidacloprid concentrations. Subsequently, amphibians collected from tile wetlands had imidacloprid brain concentrations two times higher than control animals and there were apparent differences in brain length and width measurements of the cerebellum and medulla. Exposure in the lab resulted in a dose-response relationship for imidacloprid and imidacloprid-olefin brain levels. Delayed reaction times to a food stimulus were also noted in the treatment groups. Detection of imidacloprid in neural tissue indicates this contaminant can cross the blood-brain barrier and suggests that tile drainage systems contribute to higher contaminant loads in non-target organisms and the aquatic ecosystem.



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