In partial fulfillment of the requirements for the degree of

Master of Science in Biology

in the

School of Biological Sciences

Jixiang Xu

Will defend her thesis

“EFFECTS OF SULFOXAFLOR EXPOSURE ON BOMBUS IMPATIENS”

21, July, 2025

1 PM

https://gatech.zoom.us/j/98569355573?pwd=KqgRMhQffU7Lrvl6Oh2oKhsEbSdw9v.1

Thesis Advisor:

Dr. Michael Goodisman

School of Biological Sciences

Georgia Institute of Technology

Committee Members:

Dr. Joseph Lachance

School of Biological Sciences

Georgia Institute of Technology

 Dr. Annalise Paaby

School of Biological Sciences

Georgia Institute of Technology

Abstract: This study focuses on the insecticide sulfoxaflor (SFX) that reveals that its significant threat to the common eastern bumblebee, Bombus impatiens, is not neurotoxicity but severe reproductive failure. The research hypothesis that chronic, sublethal SFX exposure would negatively impact worker bees by altering gene expression in brain and ovary tissues. While acute toxicity tests established a lethal dose (LC₅₀ of 1.2222 mg/L), the more critical findings came from chronic exposure to field-realistic concentrations (0.16mg/L and 0.31mg/L). These experiments documented severe dose-dependent behavioral and reproductive impairments, including significantly reduced nectar consumption, honey pot construction, and a cessation of egg-laying. RNA sequencing revealed a tissue-specific differential gene expression: while the brain’s gene expression remained largely unaffected, the ovary shows a massive, dose-dependent transcriptomic change. This identifies the ovary, not the brain, as the primary site of chronic SFX pathology. Functional analysis showed SFX disrupting genes essential for meiosis, cellular signaling, energy metabolism, and tissue structure.