Measurement of protein and sugar consumed by bumblebee larvae under standard and food stress conditions using lanthanide complexes

Abstract

Measurement of food consumed by larvae of progressive provisioning bees requires an experimental approach that marks the food sources appropriately. This paper aims to measure the amount of sugars and proteins consumed by a single bumblebee larva and to define, how the proportion between protein and sugar changes under stress conditions. We marked sugar and pollen sources using lanthanide (gadolinium, dysprosium) complexes with diethylene-triamine-pentaacetic acid (DTPA) chelator. We precisely quantified the amount of Gd and Dy in feces, and thus quantified linearly correlated protein and sugar consumed by males and females (workers) of Bombus terrestris during their development. We compared body mass, total amount of ingested sugar and total amount of ingested protein in colonies which are fed ad libitum and in colonies with restricted feeding. Males fed ad libitum during their development ingested 0.52 mg of protein and 4.43 mg of sugar, and workers fed ad libitum ingested 0.54 mg of protein and 4.26 mg of sugar per 1 mg of dry body weight on average. Food-stressed workers ingested 0.51 mg of protein and 4.65 mg of sugar per 1 mg of dry body weight on average. Strong positive correlation between body mass, total protein ingested, and total sugar ingested in all our experiments was present. However, the consumption of sugar grew steeper with the consumption of protein in colonies under food stress compared to the ad libitum-fed colonies. In conclusion, we show the existence of different patterns in ingestion of protein and sugar between well-fed and food-stressed bumblebee colonies.