Sub-lethal effects at stake: Does the acaricide Coumaphos and fungicide Folpet affect the hypopharyngeal glands size?

Abstract

Background: Pesticides are increasingly suspected to be involved at a global scale in honey bee decline. Most studies focuses on acute effects on mortality, whereas sub-lethal effects are poorly understood. Hypophryngeal glands (HPG), producing royal jelly to feed brood, are established marker to assess sub-lethal effects of pesticides where for example the size of the acini can be measured. The size of the later depends of different natural factors: the age of the bee and the type of task performed by the bee. The HPG are the best developed at the age of 10 days by nursing bees. Regarding the data requirements of the new EFSA bee guidance document and the recently developed OECD larva test 237 and 239 a data GAP regarding residues of PSM in the produced Royal Jelly by pesticide exposed bees which might have an adverse impact on larva development from day 1 to day 3 is recognized. Method: The effects on the commonly and widely used varroacide coumaphos in hives and the fungicide folpet in agriculture are currently unknown. Here we measured the size of the acini of new emerged bees treated with field realistic and non-realistic doses of both substances dissolved in pollen patties fed ad libitum for nine days (N=3 cages with 20 bees in each group) and in small encaged colonies without queens. An untreated and acetone control were established. The effects of the pesticides on workers and residues in gelee royal were tested with and without brood to take into consideration variations according to the tasks performed by the bees due to labor division. . After staining HPG activity was measured as a proxy via acini size. The results will be discussed. Results: Our results may help to improve knowledge in the development and validation of methods to evaluate the risk of bees exposed to pesticides for plant protection product authorization in an appropriate and comparable way which could be consequently implemented in standardized ring-test.