Changes in the bioelement content of summer and winter western honeybees (Apis mellifera) induced by Nosema ceranae infection

Abstract

Proper bioelement content is crucial for the health and wellness of all organisms, including honeybees. However, the situation is more complicated in these important pollinators due to the fact that they change their physiology during winter in order to survive the relatively harsh climatic conditions. Additionally, honeybees are susceptible to many diseases such as nosemosis, which during winter can depopulate an entire colony. Here we show that summer bees have a markedly higher content of important bioelements such as: Al, Cu, P, V, (physiologically essential); Ca, K, Mg, (electrolytic); Cr, Se, Zn, (enzymatic); As, Hg, (toxic). In contrast, a markedly higher content of: Fe (physiologically essential); Mn, Ni, (enzymatic); Cd (exclusively toxic) were present in winter bees. Importantly, N. ceranae infection resulted in an increased honeybee bioelement content of: S, Sr (physiologically essential) and Pb (exclusively toxic), whereas the Nosema-free worker-bees had higher amounts of B and Si (physiologically essential). We propose that the shortages of Fe, Mn, Ni, and Na observed in Nosema-infected bees, could be the reason for the higher mortality of Nosema-infected bees throughout overwintering. In addition, a shortage of bioelements such as B and Si may be a reason for accelerated aging in foragers that is observed following N. ceranae infection. Therefore, in winter, bioelement content was more strongly affected by N. ceranae infection than during summer. We found a strong correlation between the bioelement content of bees and seasons (summer or winter) and also with Nosema infection. We conclude that the balance of bioelements in the honeybee is altered by both seasonal affects and by Nosema infection.

Fig 1. Principal component analysis (PCA) of twenty two bioelements for honeybees from different conditions.

(a) A variable graph showing the position of the load vectors relative to the first two principal components; physiologically essential bioelements are marked in green (Al, B, Cu, Fe, P, S, Si, Sr, and V), electrolytic in black (K, Na, Ca, Cl, and Mg), enzymatic in blue (Cr, Mn, Se, Zn, and Ni) and exclusively toxic in red (Cd, Hg, Pb, and As). (b) The graph shows a strong correlation of bioelement content with seasons (summer, winter), and further with a Nosema infection.