Behavioural regulation of mineral salt intake in the adult worker honey bee, Apis mellifera

Abstract

Honey bees are important insect pollinators, which social existence displays remarkable physiological and behavioural traits. These are tightly controlled by dietary cues. Detection, selection and ingestion of food entail the regulation of nutrient intake that leads to nutritional homeostasis. This study was motivated by the lack of information on mineral salt feeding preferences and regulation by adult honey bees. Here, in laboratory-based assays, I assessed the behavioural responses associated with feeding behaviour of adult worker honey bees to eight prevalent minerals in pollen (K, Na, Mg, Ca, Fe, Zn, Cu, Mn). In Chapter 3, using the classical Proboscis Extension Reflex approach and drinking assays, I tested the gustatory responses of forager bees to single minerals in either water or nectar-like solutions at four levels of concentration. I found that foragers (mixed-age) can detect individual salts/metals mineral salts with responses depending on mineral identity. Overall, bees found low mineral levels in water phagostimulatory. But when in sucrose solutions, only high Mg, Fe and Cu were rejected. In Chapter 4, using choice cohorts, I tested whether newly-emerged bees preferred a “salty” vs. “unsalty” diet and assessed the effects of single minerals on consumption responses and survival over 6 days. I verified that young bees 1) perceived and selected specific minerals in food; 2) showed behavioural regulation of mineral intake, but not all minerals were regulated to the same extent; 3) not all minerals acted as phagostimulants at low levels, but were deterrent at sufficiently high levels. This work is one of the firsts to evaluate gustatory responses of minerals, especially metals, and, to my knowledge, the first to assess the dietary self-selection of salts and metal nutrients in the context of behavioural regulation of intake in adult worker honey bees. The current study lays the groundwork for exploring mineral salt requirements, feeding preferences and regulatory mechanisms of salt intake in honey bees. Keywords: Apis mellifera, workers, taste model, Bertrand’s rule, micronutrients, behavioural regulation, self-selection, gustation.