The impact of sublethal concentrations of copper and zinc on honey bee (Apis mellifera carnica) was investigated in our study. Bees were fed with different concentrations of copper sulphate and zinc chloride for 10 days. Number of dead bees, feeding rate and changes in behaviour were examined daily. Our results showed significant increase in death rate for both test solutions at almost every concentration. The only concentration that did not show significantly different death rate was 0.5 mM ZnCl2. LC50 for CuSO4 was determined at 0.95 mM, and 2.17 mM for ZnCl2, which shows that copper is more toxic for honeybees. Feeding rate was not significantly different than control (sucrose solution) at any concentration of both test solutions. However, graphical presentation of results for experiment with ZnCl2 show a decrease of feeding rate with increasing concentrations. At higher concentrations of both test solutions a significant and frequent change of behaviour, like dragging abdomen and uncoordinated and decreased movement intensity, was noted. For second part of our study we performed a two-choice experiment, in which we investigate honeybee preference for each of test metals. Two-choice experiment was performed for 24h and honeybees were able to choose between control sucrose solution and sucrose solution with different concentrations of CuSO4 and ZnCl2 respectively. We did not observe any significant difference in uptake between control solution and solution containing CuSO4, for any concentrations tested. . This shows no attraction or deterrence of honeybees by CuSO4 . On contrary, in experiment with ZnCl2 honeybees preferred sucrose solutions containing ZnCl2, however statistical significance was shown only for 0,5 mM ZnCl2. This indicates that bees are probably able to detect zinc chloride in a sucrose solution or a change in sweetness of sucrose solution. Further studies are needed for explanation of shown honeybee preference for zinc solutions.
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