Accelerated abdominal lipid depletion from pesticide treatment alters honey bee pollen foraging strategy, but not onset, in worker honey bees

Authors: Deeter, Megan; Snyder, Lucy; MEADOR, C.A.D. - Former ARS Employee; Corby-Harris, Vanessa

Submitted to: Journal of Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2023
Publication Date: 4/1/2023
Citation: Deeter, M.E., Snyder, L.A., Meador, C., Corby-Harris, V.L. 2023. Accelerated abdominal lipid depletion from pesticide treatment alters honey bee pollen foraging strategy, but not onset, in worker honey bees. Journal of Experimental Biology. 226(7). Article jeb245404. https://doi.org/10.1242/jeb.245404.
DOI: https://doi.org/10.1242/jeb.245404

Interpretive Summary: Food intake behavior helps maintain homeostasis. For honey bees, food intake for the entire colony is delegated to a demographic of workers that forage for pollen, nectar and water. Stressed bees may exhibit changes in foraging behavior, but the physiological mechanisms underlying these changes are unknown. We speculate that chronic stress depletes abdominal adipose tissue to disrupt appetitive patterns and increase food intake. To test this, we treated bees with pesticides and sampled them as foragers to assay both their abdominal and pollen lipid content. Stressed bees had less abdominal lipid and collected less, yet fattier pollen. Our results show that a stress-induced depletion of abdominal lipid signals a change in conscious feeding behavior to collect fattier foods.

Technical Abstract: Honey bee abdominal lipids decline with age, a change thought to be associated with the onset of foraging behavior. Stressors, such as pesticides, may accelerate this decline by mobilizing internal lipid to facilitate the stress response. Whether bees with stressor-induced accelerated lipid loss vary from controls in both the onset of foraging and nutritional quality of collected pollen is not fully understood. We asked whether stressors affect foraging behavior through the depletion of abdominal lipid, and whether stress-induced lipid depletion causes bees to forage earlier and for fattier pollen. We tested this by treating newly emerged bees with one of two pesticides, pyriproxyfen (a juvenile hormone analog) and spirodiclofen (a fatty acid synthesis disruptor), that may affect energy homeostasis in non-target insects. Bees fed these pesticides were returned to hives to observe the onset of foraging behavior. We also sampled foraging bees to assay both abdominal lipids and dietary lipid content of their corbicular pollen. Initially, spirodiclofen-treated bees had significantly more abdominal lipids, but these declined faster compared with controls. These bees also collected less, yet more lipid-rich, pollen. Our results suggest that bees with accelerated lipid decline rely on dietary lipid content and must collect fattier pollen to compensate. Pyriproxyfen treatment reduced the age at first forage but did not affect abdominal or collected pollen lipid levels, suggesting that accelerated fat body depletion is not a prerequisite for precocious foraging.