How does adulteration of wax foundation affect phenoloxidase and lysozyme activities as selected parameters of immunity in Apis mellifera?

Abstract

Introduction: The adulteration of wax foundation is, for many reasons, a growing problem of modern beekeeping not only in Europe but also around the world. Wax foundation contaminated with stearin addition leads to a brood die-off, while paraffin addition negatively affects the strength of combs. It is tenable that such adulterated wax foundation reduces bees' immunity. The aim of the study was to determine the activities of two bee immune enzymes, lysozyme and phenoloxidase, in the haemolymph of worker bees which had emerged from combs with wax foundations contaminated with stearin or paraffin.

Material and methods: Combs built with stearin- or paraffin-adulterated wax (both adulterants at concentrations of 10%, 30% or 50%) or pure wax (0% adulterated) foundations were placed in the colonies, one for each adulterant and percentage. The workers were marked upon emergence from these combs and those bees were introduced into one strong colony per adulterant and percentage. Phenoloxidase and lysozyme activities were determined in the haemolymph of 1-, 7- and 14-day-old workers.

Results: The higher the concentrations of stearin and paraffin in the wax foundation, the lower the phenoloxidase activities were. These activities increased with the bee age. In contrast, the trends in lysozymes were opposite. Paraffin seems to be less toxic than stearin.

Conclusion: Adulteration of wax foundation with even a small amount of stearin or paraffin has negative effects on the functioning of the bee.

Keywords: humoral immunity; lysozyme; paraffin; phenoloxidase; stearin; wax adulteration.

Fig. 1.

Effect of adulteration of wax foundation with paraffin and stearin on phenoloxidase (A) and lysozyme (B) activities in the haemolymph of A. mellifera worker bees PA10% – paraffin 10%, n = 30; PA30% – paraffin 30%, n = 30; PA50% – paraffin 50%, n = 30; ST10% – stearin 10%, n = 30; ST30% – stearin 30%, n = 30; ST50% – stearin 50%, n = 30; * – statistically significant difference within an age cohort between the control group and a group with a certain percentage of adulteration with paraffin or stearin (P-value ≤ 0.01); horizontal lines – statistically significant difference within an age cohort between an adulteration level of wax with paraffin and the same adulteration level of wax with stearin (P-value ≤ 0.01); a, b, c – statistically significant differences between age cohorts for the same adulteration level of wax and the same adulterant (P-value ≤ 0.01); bars and whiskers – standard deviation