Microsoft Word - 60848225-file00.docx

15 Animals strongly regulate the amount of protein that they consume. The quantity of 16 individual essential amino acids (EAAs) obtained from dietary protein depends on the 17 protein source, but how much EAA proportions in diet affect nutrient balancing has been 18 rarely studied. Recent research using the Geometric Framework for nutrition has revealed 19 that forager honeybees who receive much of their dietary EAAs from floral nectar and not 20 from solid protein have relatively low requirements for dietary EAAs. Here, we examined 21 the nutritional requirements for protein and carbohydrates of foragers of the buff-tailed 22 bumblebee, Bombus terrestris. By using protein (sodium caseinate) or an equimolar mixture 23 of the 10 EAAs, we found that the intake target (nutritional optimum) of adult workers 24 depended on the source and proportion of dietary EAAs. When bees consumed caseinate25 containing diets in a range of ratios between 1:250 and 1:25 (protein-to-carbohydrate), they 26 achieved an intake target (IT) of 1:149 w/w. In contrast to those fed protein, bees fed the 27 EAA diets had an IT more biased towards carbohydrates (1:560 w/w) but also had a greater 28 risk of death than those fed caseinate. We also tested how the dietary source of EAAs 29