Imidacloprid Pesticide Causes Unexpectedly Severe Bioelement Deficiencies and Imbalance in Honey Bees Even at Sublethal Doses

SIMPLE SUMMARY: Honey bees deliver many valuable products and pollinate many crucial crops, and pesticides impair honey bee health in many ways. It is a serious problem of the contemporary agroecosystem, but the mechanisms of these phenomena have not been sufficiently explored. Therefore, we investigated the impact of the imidacloprid pesticide (IMD) on the bioelement body content in honey bees in field experiments using both sublethal considered field-relevant (5 ppb), and adverse (200 ppb) doses, which has not been studied before. Our findings revealed for the first time that IMD causes unexpectedly severe bioelement deficiencies in 69% of bioelements (32 assayed) and disturbs the balance between the levels of the remaining ones even at sublethal doses. The increase in three toxic bioelements was alarming. Consequently, we have suggested a new physiological mechanism regarding how nicotinoids may interfere with honey bee health status. This also sets out new directions for further research, pointing to the bioelement supplementation of the diet as an important element of honey bee preventive health care when the bee farms or amateur apiaries are located in an agrocenosis exposed to pesticides. ABSTRACT: Pesticides impair honeybee health in many ways. Imidacloprid (IMD) is a pesticide used worldwide. No information exists on how IMD impact the bees’ body bioelement balance, which is essential for bee health. We hypothesized that IMD disturbs this balance and fed the bees (in field conditions) with diets containing 0 ppb (control), 5 ppb (sublethal considered field-relevant), and 200 ppb (adverse) doses of IMD. IMD severely reduced the levels of K, Na, Ca, and Mg (electrolytic) and of Fe, Mo, Mn, Co, Cu, Ni, Se, and Zn, while those of Sn, V, and Cr (enzymatic) were increased. Levels of P, S, Ti, Al, Li, and Sr were also decreased, while only the B content (physiologically essential) was increased. The increase in Tl, Pb, and As levels (toxic) was alarming. Generally, IMD, even in sublethal doses, unexpectedly led to severe bioelement malnutrition in 69% of bioelements and to a stoichiometric mismatch in the remaining ones. This points to the IMD-dependent bioelement disturbance as another, yet unaccounted for, essential metabolic element which can interfere with apian health. Consequently, there is a need for developing methods of bioelement supplementation of the honey bee diet for better preventing bee colony decline and protecting apian health status when faced with pesticides.