Effects of amitraz and age on sweetness perception, learning, and memory in Apis mellifera workers

Pesticide use in colonies of Apis mellifera (honey bee) is widespread. Determining whether these pesticides have deleterious unwanted side effects on honey bee physiology and behavior is a challenging endeavor. Amitraz is a neuroactive formamidine pesticide applied to hives to manage Varroa destructor, an ectoparasite of honey bees. It is a high affinity octopaminergic agonist. Previous studies have described various effects (or no effects) of exposure to amitraz on honey bee sucrose sensitivity, learning, and memory but have not factored in age at exposure as a variable. With the goal of improving apicultural practices, this study conducted gustatory response assays, learning trials, and memory recall trials to examine the effects of amitraz on honey bees with age as a controlled variable. Topical application of amitraz dissolved in acetone acutely increased sucrose sensitivity in foraging age bees and restored original sensitivity in newly emerged bees after acetone alone decreased it. Topical amitraz dissolved in acetone had no effect on learning and memory in intermediate age and foraging age bees, whereas acetone alone hindered performance. These results are consistent with previous demonstrations that stimulation of octopamine receptors can increase sensitivity to sucrose and facilitate olfactory association learning, and they demonstrate that amitraz has short-term effects on honey bee behavior.