Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2017
Publication Date: 1/11/2018
Citation: Corby-Harris, V.L., Snyder, L.A., Meador, C.A., Ayotte, T.C. 2018. Honey bee (Apis mellifera) nurses do not consume pollens based on their nutritional quality. PLoS One. 13(1):e0191050. https://doi.org/10.1371/journal.pone.0191050.
Interpretive Summary: Honey bees choose from a variety of floral resources from which to gather pollen, the primary source of their protein and lipid requirements. Past research has shown that bumble bees optimize the types of pollens they eat in order to optimize their health. We reasoned that honey bee nurse workers would perform similar behaviors, and prefer pollens that confer the greatest degree of tissue development. We conducted studies to assess the nutritional value of pollen and a series of assays to test whether nurses choose among natural pollen, supplemented pollens, or liquid diets with lipid and protein content similar to natural pollens. We find that, although pollen, protein, and lipids, are important for hypopharyngeal gland (HG) development, nurse bees do not discriminate between high and low quality diets. This suggests that, although certain pollens provide a greater benefit per unit of consumption, honey bee nurses either cannot or do not discriminate among pollens based on nutrition.
Technical Abstract: Honey bees (Apis mellifera) consume a variety of pollens to meet the majority of their requirements for protein and lipids. Recent work indicates that at both the colony and individual levels, honey bees prefer diets that reflect the proper ratio of nutrients necessary for optimal survival and homeostasis. This idea relies on the precept that honey bees evaluate the nutritional composition of the foods provided to them. While this has been shown in bumble bees, the data for honey bees are mixed. Here, we tested the hypothesis that honey bee nurses choose diets that optimize their development. We first determined the nutritional profile, number of plant taxa (richness), and degree of hypopharyngeal gland (HG) growth conferred by three honey bee collected pollens. We then presented nurses with these same three pollens in paired choice assays and measured consumption. To test whether the content or ratios of these macronutrients influenced preference, we presented bees with natural pollens supplemented with protein or lipids and liquid diets with protein and lipid ratios equal to the natural pollens. Different pollens conferred different degrees of HG growth, and nutritious pollens had higher levels of certain nutrients and lower protein to lipid ratios. Plant taxon richness did not influence HG size. Bees did not always choose the most nutritious pollens. Adding protein and/or lipids to less desirable pollens minimally increased pollen attractiveness, and nurses did not exhibit a strong preference for any of the three liquid diets. We conclude that different pollens provide different nutritional benefits, taxon richness does not impact HG size, and choice does not reflect pollen nutritional value.