Comparative toxicity of oral exposure to paraquat: Survival rates and gene expression in two honey bee species; Apis mellifera and Apis cerana

Authors: PATCHARIN, PHONKASEM - Chiang Mai University; TERD, DISAYATHANOOWAT - Chiang Mai University; THUNYARAT, CHANTAPHANWATTA - Chiang Mai University; CHAINARONG, SINPOO - Chiang Mai University; Chen, Yanping; Evans, Jay; HO, LEE - Konkuk University; KRONGDANG, SASIPRAPA - Burapha University

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2024
Publication Date: 12/1/2024
Citation: Patcharin, P., Terd, D., Thunyarat, C.N., Chainarong, S., Chen, Y., Evans, J.D., Ho, L., Krongdang, S. 2024. Comparative toxicity of oral exposure to paraquat: Survival rates and gene expression in two honey bee species; Apis mellifera and Apis cerana. Environmental Pollution. 362. Article 125026. https://doi.org/10.1016/j.envpol.2024.125026.
DOI: https://doi.org/10.1016/j.envpol.2024.125026

Interpretive Summary: Honey bee populations are at risk for environmental stress, disease, and limited nutrition. We do not yet have a full understanding of how environmental chemicals affect bee health. We also need to know how different bee species react to chemical stress. This collaborative study presents the mortality risk of paraquat to honey bees, and also shows how bees react to this stress. the results can be expanded to similar chemicals in use in the US to better deterimine potential activity and risks in the honey bee a key managed pollinator for agriculture.

Technical Abstract: Honey bees provide vital pollination services to agricultural crops and wild plants worldwide. Unfortunately, incidents harming honey bees have been on the rise in recent years due to the overuse of pesticides in agricultural production. Among the commonly utilized bee species in beekeeping are Apis cerana and Apis mellifera, with wild A. cerana populations widely dispersed in forests, contributing substantially to ecosystem balance. Yet, the impact of paraquat, a toxic herbicide, on A. cerana remains largely unexplored. This study aims to address this gap by examining acute exposure endpoints based on mortality represented by median lethal doses (LD50 values) of paraquat, and survival rates of both A. cerana and A. mellifera. Additionally, the study delves into the alterations in gene expression patterns between the two bee species—specifically related to detoxification, antioxidants, metabolism, and immune responses—following exposure to lethal doses of paraquat. The findings revealed that A. cerana exhibits greater sensitive to paraquat compared to A. mellifera. The acute oral LD50 values for A. cerana were 5.85, 1.74, and 1.21 µg/bee, whereas the corresponding values for A. mellifera were 104.00, 11.00, and 6.41 µg/bee for A. mellifera at 24, 48, and 72 h, respectively. Further, the study demonstrated significant upregulation of detoxification enzymes SOD1, CAT, and LLDH-X2 in both A. mellifera and A. cerana following exposure to paraquat, while SOD2 expression was notably downregulated in both species. This research provides a rare comparison of the effects of chemical stress on morbidity and gene expression in different honey bee species, providing a foundational framework for risk assessment and the regulation of herbicide risks to pollinating insects. Paraquat was shown to be moderately toxic to honey bees A. mellifera but highly toxic to A. cerana, indicating the importance of screening multiple bee species when assessing the risks of chemical exposure.