Beside many beneficial applications in industry, agriculture andmedicine, 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. (c) 2018 Elsevier B.V. All rights reserved.