Unbalanced fatty acid diets impair discrimination ability of honey bee workers to damaged and healthy brood odors

Authors: Bennett, Meghan; Welchert, Ashley; Carroll, Mark; SHAFIR, S. - Hebrew University Of Jerusalem; SMITH, B. - Arizona State University; Corby-Harris, Vanessa

Submitted to: Journal of Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2022
Publication Date: 4/7/2022
Citation: Bennett, M.M., Welchert, A.C., Carroll, M.J., Shafir, S., Smith, B., Corby-Harris, V.L. 2022. Unbalanced fatty acid diets impair discrimination ability of honey bee workers to damaged and healthy brood odors. Journal of Experimental Biology. 225(7);jeb244103. https://doi.org/10.1242/jeb.244103.
DOI: https://doi.org/10.1242/jeb.244103

Interpretive Summary: Honey bee colonies rely on adequate nutrition to perform essential colony functions. Young worker bees eat pollen, while older workers consume mostly nectar. Pollen is nutrient dense, containing lipids and proteins vital for young worker so they can develop glands that produce food for developing babies. One problem is honey bee colonies go through significant nutritional dearths seasonally, and when being used for pollination services in mono-culture settings. Without diverse pollen available, bees can be consuming nutritionally unbalanced diets. Previous studies have showed diets unbalanced in fatty acids impaired cognition of bees. We asked the question, do these unbalanced diets affect young worker bee ability to tell the difference between damaged and healthy babies? Young worker bees use their sense of smell to locate diseased or dead nest mates. Thus, we tested the hypothesis that young worker bees fed unbalanced diets would impair their ability to sniff out the dead. We trained bees to learn healthy or damaged baby odors and tested their ability to tell the difference between the two when fed balanced or unbalanced diets. Balanced fatty acid diets enabled bees to tell the difference, but unbalanced diets impaired their ability to tell the difference between damaged and healthy odors. These data are encouraging that fatty acids are an important angle to study how nutrition affects cognition and behavior. It is possible that if a colony can not sniff out the dead, then they could be more prone to spreading of disease in the hive.

Technical Abstract: Nutrition supports social insect colonies by regulating both individual performance and colony growth. In honey bee colonies, task-related behaviors such as nursing and foraging are partially mediated by nutrition. Young workers (nurses) consume almost all of the pollen in the hive, while foragers consume mostly nectar. Pollen provides vital proteins and lipids, consumed by nurse bees for approximately 1 week post-eclosion. The role that lipids play in the physiology and behavior of adult bees is gaining significant attention. Recent research suggests that diets with balanced ratios of fatty acids increase olfactory learning in honey bees. Olfaction is crucial for young worker bees to perform brood care and cell cleaning behaviors, which is important for hive health and disease control. Thus, we targeted the early adult, pollen-feeding stage to examine how fatty acids affect cognition to hive-relevant odors. We fed young workers (days 0–9) diets balanced or unbalanced in their ratio of essential fatty acids ('-6:3) sourced from pollen or cooking oils. We then measured their ability to learn healthy and damaged brood odors, as well as their ability to discriminate between the two. Workers fed balanced diets could learn and discriminate between brood odors better than workers fed unbalanced diets. Consumption of both diet types decreased with age, but their cognitive effects remained. These results suggest that diet affects young worker cognitive development, which may affect task-related behaviors and colony hygiene.