Effects of heat wave combined with sublethal doses of thiamethoxam on oviposition performance and gut microbial community of
- 1Eastern Bee Research Institute, College of Animal Science and Technology, Yunnan Agricultural University, Kunming 650201, China
- 2Corresponding authors.
Abstract
Climate warming has increased the frequency and intensity of extreme heat events, while neonicotinoid insecticides such as thiamethoxam are widely applied in agroecosystems. These two stressors frequently co-occur, yet their combined effects on pollinator health remain poorly understood. Here, we aimed to investigate the individual and interactive impacts of sublethal thiamethoxam and heat stress on bumblebee microcolonies. We examined the median lethal concentration (LC₅₀), food intake, survival rate, oviposition performance, biochemical activity, gene expression, and gut microbiota in Bombus terrestris microcolonies. The findings revealed that thiamethoxam and heat stress, alone and in combination, exerted effects on bumblebees across different dimensions. Heat stress markedly weakened worker tolerance to thiamethoxam: the LC₅₀ at 32 °C was 0.69 times and 0.52 times that at 26 °C at the 24 h and 48 h time points, respectively. Food intake declined significantly under all three exposure scenarios, whereas survival remained unaffected. The combined treatment significantly altered egg size and VgR expression. Heat stress offset the thiamethoxam-induced decline in SOD and GSH, but MDA remained elevated, indicating that maintained antioxidant markers did not restore protection against lipid peroxidation. Neither thiamethoxam nor heat stress, whether applied singly or in combination, significantly changed the alpha diversity indices of the gut microbiota; however, the microbial community composition underwent marked restructuring. The heat stress alone group yielded the highest number of unique ASVs. Thiamethoxam treatment noticeably shifted the gut microbial community profile, and the combined treatment produced a shift similar to that of thiamethoxam alone but with additional synergistic modulation. LEfSe analysis identified distinct sets of differentially abundant bacterial taxa across the treatment groups, confirming substantial community restructuring; the heat stress alone group harbored the largest number of significantly discriminant taxa. Overall, heat stress synergistically amplifies the sublethal toxicity of thiamethoxam in bumblebees, altering egg traits and reproductive gene expression and reshaping the gut microbiota, which underscores the urgency of incorporating temperature scenarios into pesticide risk assessment and pollinator conservation strategies.
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BibTeX
@article{xu2026effects,
title = {{Effects of heat wave combined with sublethal doses of thiamethoxam on oviposition performance and gut microbial community of}},
author = {Xi Xu and Shuang Wang and Yunfei Xue and Shaozi Xu and Rujie He and Dan Yue and Danyin Zhou and Kun Dong and Yakai Tian},
journal = {Ecotoxicology and Environmental Safety},
year = {2026},
month = nov,
doi = {10.1016/j.ecoenv.2026.121013},
url = {https://doi.org/10.1016/j.ecoenv.2026.121013},
note = {CC BY},
}
RIS
TY - JOUR
TI - Effects of heat wave combined with sublethal doses of thiamethoxam on oviposition performance and gut microbial community of
AU - Xi Xu
AU - Shuang Wang
AU - Yunfei Xue
AU - Shaozi Xu
AU - Rujie He
AU - Dan Yue
AU - Danyin Zhou
AU - Kun Dong
AU - Yakai Tian
PY - 2026
DA - 2026/11/05
JO - Ecotoxicology and Environmental Safety
DO - 10.1016/j.ecoenv.2026.121013
UR - https://doi.org/10.1016/j.ecoenv.2026.121013
AB - Climate warming has increased the frequency and intensity of extreme heat events, while neonicotinoid insecticides such as thiamethoxam are widely applied in agroecosystems. These two stressors frequently co-occur, yet their combined effects on pollinator health remain poorly understood. Here, we aimed to investigate the individual and interactive impacts of sublethal thiamethoxam and heat stress on bumblebee microcolonies. We examined the median lethal concentration (LC₅₀), food intake, survival rate, oviposition performance, biochemical activity, gene expression, and gut microbiota in Bombus terrestris microcolonies. The findings revealed that thiamethoxam and heat stress, alone and in combination, exerted effects on bumblebees across different dimensions. Heat stress markedly weakened worker tolerance to thiamethoxam: the LC₅₀ at 32 °C was 0.69 times and 0.52 times that at 26 °C at the 24 h and 48 h time points, respectively. Food intake declined significantly under all three exposure scenarios, whereas survival remained unaffected. The combined treatment significantly altered egg size and VgR expression. Heat stress offset the thiamethoxam-induced decline in SOD and GSH, but MDA remained elevated, indicating that maintained antioxidant markers did not restore protection against lipid peroxidation. Neither thiamethoxam nor heat stress, whether applied singly or in combination, significantly changed the alpha diversity indices of the gut microbiota; however, the microbial community composition underwent marked restructuring. The heat stress alone group yielded the highest number of unique ASVs. Thiamethoxam treatment noticeably shifted the gut microbial community profile, and the combined treatment produced a shift similar to that of thiamethoxam alone but with additional synergistic modulation. LEfSe analysis identified distinct sets of differentially abundant bacterial taxa across the treatment groups, confirming substantial community restructuring; the heat stress alone group harbored the largest number of significantly discriminant taxa. Overall, heat stress synergistically amplifies the sublethal toxicity of thiamethoxam in bumblebees, altering egg traits and reproductive gene expression and reshaping the gut microbiota, which underscores the urgency of incorporating temperature scenarios into pesticide risk assessment and pollinator conservation strategies.
SN - 0147-6513
SN - 1090-2414
ER -