Sublethal effects of chronic exposure to CdO or PbO nanoparticles or their binary mixture on the honey bee (Apis millefera L.)

Cadmium and lead-based nanotechnologies are increasingly used in agricultural, industrial, and biological processes; however, potential adverse effects of nanomaterials on honey bees had not been assessed. In this study, effects of exposures to sublethal concentrations of PbO and CdO nanoparticles (NPs), either separately or in combination on honey bee (Apis mellifera) workers, were assessed. Honey bee workers were orally exposed for 9 days under laboratory conditions to sublethal concentrations (20% of LC50) of CdO (0.01 mg/ml⁻) and PbO (0.65 mg/ml⁻) NPs either separately or combined. Effects on survival, feeding rate, activity of acetylcholinesterase (AChE), and expression of selected stress-related detoxifying enzymes were quantified. Survival and feeding rates decreased particularly in bees fed sugar syrup containing CdO NPs or binary mixtures of NPs of both metal oxides. Expressions of genes involved in detoxification of xenobiotics were affected by various combinations. Expression of catalase was 13.6-fold greater in bees consumed sugar syrup diet containing binary mixture of sublethal concentrations of both CdO and PbO NPs than it was in unexposed, control bees. AChE activity in heads of honey bees was inhibited by 3.8-, 3.0-, and 2.8-fold relative to control, respectively, in response to exposure to Cd or/and Pb oxide NPs. This result indicates potential neurotoxic effects of these NPs to honey bees. CdO NPs exhibited greater potency to honey bees. Overall, sublethal concentrations of CdO or/and PbO NPs resulted in detrimental effects on honeybee workers.

• October 2018 
• • • Environmental Science and Pollution Research

• DOI: 
• 10.1007/s11356-018-3314-2
• • • Yahya Al Naggar
    • Khaled Dabour
    • Saad H. D. Masry

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Cellular alterations in midgut cells of honey bee workers (Apis millefera L.) exposed to sublethal concentrations of CdO or PbO nanoparticles or their binary mixture

Beside many beneficial applications in industry, agriculture and medicine, nanoparticles (NPs) released into the environment might cause adverse effects. In the present study, effects of exposure to sublethal concentrations of PbO and CdO NPs, either separately or in combination on honey bee (A. mellifera) workers were assessed. Honey bee workers were fed sugar syrup contained (20 % of LC50) of CdO (0.01 mg ml-1) and PbO (0.65 mg ml-1) NPs either separately or combined for nine days under laboratory conditions. Control bees were fed 1.5 M sucrose syrup without NPs. Effects on histological and cellular structure of mid gut cells were investigated using light and electron microscope. Percentages of incidence of apoptosis or/and necrosis in mid gut cells were also quantified by use of flow cytometry. Rapture of the peritrophic membrane (PM) was among the most observed histopathological alteration in bees fed sugar syrup contained CdO NPs separately or combined with PbO NPs. Common cytological alterations observed in epithelial cells were irregular distribution or/and condensation of nuclear chromatin, mitochondrial swelling and lysis, and rough endoplasmic reticulum (rER) dilation, fragmentation, and vesiculation and were quite similar in all treated groups compared to control. The greatest incidence (%) of necrosis was observed in bees fed the diet that contained CdO NPs alone. The greatest % of both apoptosis and necrosis was observed in bees fed sugar syrup spiked with sublethal concentrations of both metal oxide NPs. Joint action of the binary mixture of Cd and Pb oxide NPs on honey bees was concluded to be antagonistic. Collectively, exposure of honey bees to these metal oxide NPs even at sublethal concentrations will adversely affect viability of the colony and further studies are still required to determine the effects of these metal oxide NPs on behavior and pollination ecology of honeybees.

• September 2018
• Science of The Total Environment 651(2019):1356–1367

• DOI: 
• 10.1016/j.scitotenv.2018.09.311

• Khaled Dabour
• Yahya Al Naggar
• Saad H. D. Masry

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