Imidacloprid Effects on the Survival and Cutaneous Microbiome of Northern Leopard Frogs

Author

• Evelyn Margaret OsterlooFollow

Date of Award

Spring 2026

Document Type

Honors Thesis

Department/Major

Biology

First Advisor

Jacob Kerby

Second Advisor

David Swanson

Third Advisor

Jeff Wesner

Keywords

Northern Leopard frogs (Lithobates pipiens), neonicotinoid insecticide, bacteria, microbial diversity, Batrachochytrium dendrobatidis, chytridiomycosis

Subject Categories

Biology | Environmental Health | Environmental Health and Protection | Environmental Microbiology and Microbial Ecology | Microbial Physiology | Organismal Biological Physiology | Other Animal Sciences | Toxicology

Abstract

Amphibians are experiencing population declines due to habitat loss, climate change, and diseases, particularly chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis. Protection from this fungal infection stems from the cutaneous microbiome. Pesticides have been shown to affect amphibians in a variety of ways, including reducing survival, locomotor performance, and accumulation in body tissues. Pesticides may also lead to changes in the cutaneous microbiome affecting amphibians who rely on these organisms as an anti-Bd defense mechanism. To investigate the effect of imidacloprid, a neonicotinoid insecticide, Northern Leopard frogs (Lithobates pipiens) were subjected to sublethal concentrations (control = 0 μg/L, low =1 μg/L, high = 10 μg/L) in captivity for 21 days. Bacterial DNA was extracted for 16S rRNA analysis to determine abundance of bacterial species in microbiomes. Survival probability was analyzed showing a statistically meaningful reduction in the survival time under the low dose treatment (low dose, 5.47 days (CrI: 3.04 -10.78), high dose, 13.21 days (CrI: 8.69-17.69), and the untreated control, 19.17 days (CrI: 13.71 – 20.93)). There was a 97.4% probability that survival differed between the control and low-dose groups, a 90.2% probability of difference between the high and low-dose groups, and a 75.7% probability of difference between the high and control groups. Treatment had no significant effect on alpha or beta microbial community diversity but time in captivity altered both alpha and beta diversity (alpha diversity: p < 0.001, beta diversity: p = 0.001). Additionally, there was a qualitative decrease in the abundance of Pseudomonadacea bacterial species. These results reveal the host and microbiome level effects of pesticide exposure on amphibians and encourage further investigation into the antifungal properties of the differentially abundant bacteria in these samples.

Recommended Citation

Osterloo, Evelyn Margaret, "Imidacloprid Effects on the Survival and Cutaneous Microbiome of Northern Leopard Frogs" (2026). Honors Thesis. 413.
https://red.library.usd.edu/honors-thesis/413