Nutritional balance of essential amino acids and carbohydrates of the adult worker honeybee depends on age

Abstract

Dietary sources of essential amino acids (EAAs) are used for growth, somatic maintenance and reproduction. Eusocial insect workers such as honeybees are sterile, and unlike other animals, their nutritional needs should be largely dictated by somatic demands that arise from their role within the colony. Here, we investigated the extent to which the dietary requirements of adult worker honeybees for EAAs and carbohydrates are affected by behavioural caste using the Geometric Framework for nutrition. The nutritional optimum, or intake target (IT), was determined by confining cohorts of 20 young bees or foragers to liquid diets composed of specific proportions of EAAs and sucrose. The IT of young, queenless bees shifted from a proportion of EAAs-to-carbohydrates (EAA:C) of 1:50 towards 1:75 over a 2-week period, accompanied by a reduced lifespan on diets high in EAAs. Foragers required a diet high in carbohydrates (1:250) and also had low survival on diets high in EAA. Workers exposed to queen mandibular pheromone lived longer on diets high in EAA, even when those diets contained 5× their dietary requirements. Our data show that worker honeybees prioritize their intake of carbohydrates over dietary EAAs, even when overeating EAAs to obtain sufficient carbohydrates results in a shorter lifespan. Thus, our data demonstrate that even when young bees are not nursing brood and foragers are not flying, their nutritional needs shift towards a diet largely composed of carbohydrates when they make the transition from within-hive duties to foraging.Electronic supplementary materialThe online version of this article (doi:10.1007/s00726-014-1706-2) contains supplementary material, which is available to authorized users.

Macronutrient ratios in pollen shape bumble bee ( Bombus impatiens ) foraging strategies and floral preferences

“…Although the nutritional requirements of bees vary throughout their lifetime and differ substantially between developing brood and adult foragers (9,42), the foraging preferences of B. impatiens workers in our study remained consistent in the presence and absence of their mother colony. In our experiment involving the foraging of host-plant pollen, workers collected pollen for their colonies, which had queens and developing larvae.…”

“…3 and 4), although lipids appeared to have had a phagostimulatory effect at lower concentrations. Thus, B. impatiens, and likely other bumble bee and generalist bee species, appears to have a sophisticated ability to assess pollen nutritional quality and forage selectively to reach nutritional intake targets (6,(41)(42)(43).…”

“…4). Additional studies are needed to determine if these ratios are optimal to support bumble bee fitness (6,42,43). Indeed, in studies using the geometric framework for nutrition approach (6,60,61), bees can regulate their protein and carbohydrate intake (42,43), and other arthropod species can regulate their protein and lipid intake to support fitness (37)(38)(39).…”

Antioxidant supplementation can reduce the survival costs of excess amino acid intake in honeybees

“…Similarly, excess intake of amino acids can reduce survival in insects (Paoli et al, 2014;Troen et al, 2007) and mammals (Miller et al, 2005). The physiological costs of eating these nitrogen rich nutrients are not well understood but may include the production of nitrogenous waste, which can have toxic effects (Wright, 1995), disruption of immune function (Povey et al, 2009) and interference with cellular signalling pathways (Simpson and Raubenheimer, 2009).…”

“…A poor diet, due to land use changes reducing the availability and diversity of floral resources, may help drive these declines (Vanbergen and the Insect Pollinators Initiative, 2013). In keeping with this idea, nutrition is a key determinant of honeybee survival (Altaye et al, 2010;Archer et al, 2014a): African honeybees (Apis mellifera scutellata) fed high protein diets experience reduced survival and European honeybees (Apis mellifera) survive poorly when fed diets rich in essential amino acids (EAAs) (Paoli et al, 2014). To protect declining and threatened honeybee populations (Pirk et al, 2014) it is important that we better understand the association between diet and honeybee survival, and find ways of mitigating the costs of poor nutrition, especially in populations which are underrepresented in the literature (Archer et al, 2014b).…”