Salt preferences of honey bee water foragers

Abstract

The importance of dietary salt may explain why bees are often observed collecting brackish water, a habit that may expose them to harmful xenobiotics. However, the individual salt preferences of water-collecting bees were not known. We measured the proboscis extension reflex (PER) response of Apis mellifera water foragers to 0-10% w/w solutions of Na, Mg and K, ions that provide essential nutrients. We also tested phosphate, which can deter foraging. Bees exhibited significant preferences, with the most PER responses for 1.5-3% Na and 1.5% Mg. However, K and phosphate were largely aversive and elicited PER responses only for the lowest concentrations, suggesting a way to deter bees from visiting contaminated water. We then analyzed the salt content of water sources that bees collected in urban and semi-urban environments. Bees collected water with a wide range of salt concentrations, but most collected water sources had relatively low salt concentrations, with the exception of seawater and swimming pools, which had >0.6% Na. The high levels of PER responsiveness elicited by 1.5-3% Na may explain why bees are willing to collect such salty water. Interestingly, bees exhibited high individual variation in salt preferences: individual identity accounted for 32% of variation in PER responses. Salt specialization may therefore occur in water foragers.

A matter of taste: the adverse effect of pollen compounds on the pre-ingestive gustatory experience of sugar solutions for honeybees

“…Bees were not pre-fed water like in some other studies (e.g. Pankiw et al 2001 ) and some might have been thirsty as response levels came close to those found in water collecting foragers that were stimulated with pure water (around 30–60% PE, Lau and Nieh 2016 ). But importantly, we did not see an increase in response to sucrose in the control (S) group over time.…”

The nutritional geography of ants: Gradients of sodium and sugar limitation across North American grasslands

“…This Na and K must be replenished. Solutions laced with Na are attractive to pollinators (Arms et al, ; Lau & Nieh, ), and floral nectars can vary 24‐fold in Na concentration within plant communities (Hiebert & Calder, ). We suggest the working hypothesis that gives Na a more functional role in plant community ecology, one in which the plants spike nectar and exudates with Na required to attract mutualists and deter enemies.…”

Ecological stoichiometry of the honeybee: Pollen diversity and adequate species composition are needed to mitigate limitations imposed on the growth and development of bees by pollen quality

“…Even if 100% Na assimilation is considered, it is unlikely that bees concentrate the scarce Na available in pollen to a great extent, and nectar cannot serve as a source of nutritional elements other than C. Thus, it is likely that the bees supplement Na from sources other than pollen and nectar. For bees, the source of non-C elements may be “dirty water”, as honeybees are known to willingly utilize liquid waste and “dirty water”, which are rich in decomposing matter and salts [ 89 , 90 ]. We hypothesize that bees are able to produce stoichiometrically balanced jelly for the reared larvae by supplementing Na deficiencies with “dirty water”.…”