About the dose-dependent effect of exogenous 20-hydroxyecdysone on the hypopharyngeal gland and behavior of adult bees Apis mellifera L.

20-Hydroxyecdysone (20E) is a biologically active substance that has multiple effects on both vertebrates and invertebrates. In arthropods, the steroid hormone 20E is primarily known as the molting hormone in imaginal phases; relatively recent studies indicate the activity of 20E on imago. However, the results of studies of its effects are contradictory, and an attempt to commercially use 20E preparations in beekeeping was unsuccessful, probably due to the tolerance of Apis mellifera L. to exogenous 20E due to increased metabolism or activation of the blood-brain barrier. In the present work, in a model experiment, we have shown that the biological effect of 20E on young bees is manifested in a dose-dependent effect on food storage in honeycomb cells, on the development of the pharyngeal gland, and the accumulation of proline secreted by it in honey. The aim of the study was to identify the dose of exogenous 20E that activates the compensatory reaction to its intake into the body, and peculiarities of this reaction. In a laboratory experiment, 50 newly emerged workers each were supplied with 50 % sugar syrup, an empty comb and kept in 120×105×40 mm cages in a hygrothermostat at 35.0±0.2 °С and relative air humidity 50±5 % for 7 days. The sugar syrup in the experiment contained the additive 20E at a concentration of 4×10-10 to 1×10-5 mol/l with daily dose from 0.01 to 250 pmol per bee. The lowest studied daily dose of 20E (0.01 pmol per bee) does not have a significant effect on the size of the hypopharyngeal gland acini. The maximum reduction (by 1/4, p 1/5, p -10 to 2×10-9 mol/l (from 0.01 to 0.05 pmol/bee per day). We suggest that 20E fed at a daily dose of 0.05 pmol per bee activates oxidation of 20E, causing a decrease in the 20E accumulation in the hemolymph and a sharp change in the influence, including change to the opposite biological effects.