Abstract
Honeybees (Apis mellifera) can be exposed via numerous potential pathways to ambient nanoparticles (NPs), including rare earth oxide (REO) NPs that are increasingly used and released into the environment. Gut microorganisms are pivotal in mediating honeybee health, but how REO NPs may affect honeybee health and gut microbiota remains poorly understood. To address this knowledge gap, honeybees were fed pollen and sucrose syrup containing 0, 1, 10, 100, and 1000mgkg−1 of nano-La2O3 for 12days. Nano-La2O3 exerted detrimental effects on honeybee physiology, as reflected by dose-dependent adverse effects of nano-La2O3 on survival, pollen consumption, and body weight (p<0.05). Nano-La2O3 caused the dysbiosis of honeybee gut bacterial communities, as evidenced by the change of gut bacterial community composition, the enrichment of pathogenic Serratia and Frischella, and the alteration of digestion-related taxa Bombella (p<0.05). There were significant correlations between honeybee physiological parameters and the relative abundances of pathogenic Serratia and Frischella (p<0.05), underscoring linkages between honeybee health and gut bacterial communities. Taken together, this study demonstrates that nano-La2O3 can cause detrimental effects on honeybee health, potentially by disordering gut bacterial communities. This study thus reveals a previously overlooked effect of nano-La2O3 on the ecologically and economically important honeybee species Apis mellifera.
Highlights
Honeybees (e.g., Apis mellifera) provide essential pollination services for agricultural ecosystems and valuable apiary products for human nutritional needs (Klein et al, 2007)
La residue in the honeybees treated with medium dosage (10 mg kg−1) nano-La2O3 exposure were comparable to the background La residue in wild honeybees (p > 0.05; Figure 1)
The medium dosage of nano-La2O3 used in this study could be taken into account to predict the natural La exposure to honeybees, it remains a challenge to characterize the complex forms of La during translocation in environmental matrices (Ma et al, 2011; Li et al, 2014)
Summary
Honeybees (e.g., Apis mellifera) provide essential pollination services for agricultural ecosystems and valuable apiary products for human nutritional needs (Klein et al, 2007). The fertilizers, pesticides, and germination stimulants containing or engineered with REO NPs have been widely used to enhance the efficiency and sustainability of agricultural practices, and nano-La2O3 is reported to account for approximately 30% of REO NPs additives and have higher cytotoxicity compared with other REO NPs (De la Torre Roche et al, 2015; Mastronardi et al, 2015; Servin et al, 2015; Gao et al, 2017) This make honeybees highly susceptible to the exposure and toxicity of REO NPs, through contacting with and ingesting these particles directly or indirectly from the surrounding environments, especially the agricultural ones, such as plant and flower surfaces, pollen and nectar, and soil and dust (Ma et al, 2011; De la Torre Roche et al, 2015; Kos et al, 2017; RadziwillBienkowska et al, 2018). Despite the fact that honeybee gut microorganisms take important roles in maintaining host immunity, metabolism, and health (Kwong and Moran, 2016), it is unknown whether and how REO NPs exposure will cause deterioration of honeybee health and dysbiosis of honeybee gut microbiota and whether the gut dysbiosis will further mediate the toxic effect of environmental contaminants on honeybees health
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