title: 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.
authors.affiliation: University of California San Diego, Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, 9500 Gilman Drive, MC0116, La Jolla, CA 92093-0116, USA plau0168@tamu.edu.
authors.forename: Pierre W
authors.initials: PW
authors.lastname: Lau
authors.affiliation: University of California San Diego, Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, 9500 Gilman Drive, MC0116, La Jolla, CA 92093-0116, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Nieh
mesh_terms: D000818:Animals; D001070:Appetitive Behavior; D001516:Bees / Q000502:physiology*; D005247:Feeding Behavior; D008274:Magnesium; D010710:Phosphates; D011188:Potassium; D012018:Reflex; D054712:Salinity; D012623:Seawater; D012964:Sodium; D014867:Water / Q000737:chemistry*
chemical_list: D010710:Phosphates; D014867:Water; D012964:Sodium; D008274:Magnesium; D011188:Potassium
keywords: Apis mellifera; PER; Salt concentration; Sodium preference; Water foraging