How to know which food is good for you: bumblebees use taste to discriminate between different concentrations of food differing in nutrient content

Abstract

In view of the ongoing pollinator decline, the role of nutrition in bee health has received increasing attention. Bees obtain fat, carbohydrates and protein from pollen and nectar. As both excessive and deficient amounts of these macronutrients are detrimental, bees would benefit from assessing food quality to guarantee an optimal nutrient supply. While bees can detect sucrose and use it to assess nectar quality, it is unknown whether they can assess the macronutrient content of pollen. Previous studies have shown that bees preferentially collect pollen of higher protein content, suggesting that differences in pollen quality can be detected either by individual bees or via feedback from larvae. In this study, we examined whether and, if so, how individuals of the buff-tailed bumblebee (Bombus terrestris) discriminate between different concentrations of pollen and casein mixtures and thus nutrients. Bumblebees were trained using absolute and differential conditioning of the proboscis extension response (PER). As cues related to nutrient concentration could theoretically be perceived by either smell or taste, bees were tested on both olfactory and, for the first time, chemotactile perception. Using olfactory cues, bumblebees learned and discriminated between different pollen types and casein, but were unable to discriminate between different concentrations of these substances. However, when they touched the substances with their antennae, using chemotactile cues, they could also discriminate between different concentrations. Bumblebees are therefore able to discriminate between foods of different concentrations using contact chemosensory perception (taste). This ability may enable them to individually regulate the nutrient intake of their colonies.

Macronutrient ratios in pollen shape bumble bee ( Bombus impatiens ) foraging strategies and floral preferences

“…In the field, we observed bees antennating pollen, potentially assessing its quality. Bumble bees appear to determine pollen quality by its protein content through tactile chemoreceptors and show preferences for high-protein pollen (26,52), whereas honey bees do not appear to share the same preference (25,29,30). Although both species may be sensitive to protein quality, the preferences observed in previous studies may reflect species-specific differences in nutritional requirements for protein and lipids.…”

“…While foraging in the same landscape, bumble bees foraged preferentially on plant species with higher protein content than did honey bees (25), suggesting species-specific differences in protein acquisition. Bumble bee workers can taste and discriminate among diets with different protein or pollen concentrations (26), and their foraging activity has been positively correlated with pollen protein content using modified (diluted with cellulose powder) single-source pollen diets (27,28) or a single plant species in which pollen protein content varied with soil conditions (20). [Note that in field studies honey bees do not appear to forage preferentially on pollen with higher protein concentrations (29,30)].…”

Consistent pollen nutritional intake drives bumble bee (Bombus impatiens) colony growth and reproduction across different habitats

“…Evolutionarily, this preference aligns with a goal of providing optimal resources for their brood, because suboptimal pollen quality can lead to reproductive deficit, egg cannibalism, and larval ejection (Génissel, Aupinel, Bressac, Tasei, & Chevrier, 2002; Tasei & Aupinel, 2008). In the laboratory, bumble bees prefer pollen diets with higher protein concentrations (Kitaoka & Nieh, 2008; Konzmann & Lunau, 2014; Ruedenauer, Spaethe, & Leonhardt, 2015; Ruedenauer et al., 2016), and these preferences extend to the field among plant species or within the same species (Cardoza et al., 2012; Hanley et al., 2008). Furthermore, bumble bee colonies will increase their foraging efforts to higher quality pollen (or nectar), or reduce foraging efforts to low‐quality pollen, even if no alternative is available (Dornhaus & Chittka, 2001, 2004; Kitaoka & Nieh, 2008).…”

Support for the reproductive ground plan hypothesis in a solitary bee: links between sucrose response and reproductive status

“…The dietary needs and mechanisms that regulate variation in nectar and pollen preferences have been well documented for honeybees (Apis mellifera) [1 -6] and bumblebees (Bombus sp.) [7][8][9], but almost nothing is known of the nutritional preferences of solitary bees or the mechanisms underlying these preferences. This is important, because one of the major causes of global bee decline is reduced availability of floral resources [10 -12].…”