Resistance to nutritional stress in ants: when being fat is advantageous

Abstract

In ants, nutrient acquisition for the whole colony relies on a minority of workers, the foragers, which are often old and lean. Some studies have shown that the link between age, physiology and foraging activity is more flexible than once thought, especially in response to colony or environmental perturbations. This great plasticity offers the intriguing possibility to disentangle the effect of age, behaviour and physiology on the ants' abilities to cope with nutritional stresses. In this paper, we first looked at the capacity of groups of foragers and inner-nest workers to resist starvation and macronutrient imbalance. Second, we investigated whether behavioural task reversion modified the tolerance to nutritional stresses and by extension, changed mortality rate. We found that inner-nest workers live longer than foragers under nutritional stresses but not under optimal conditions. The reversion from foraging to inner-nest activities is followed by an increase in fat content and longevity. Finally, we demonstrated that changes in fat content associated with behavioural transition are highly flexible and strongly correlated to tolerance of nutritional stress. Our results have considerable implications for our understanding of the population dynamics of social insects under adverse nutritional conditions.

Parsing the life-shortening effects of dietary protein: effects of individual amino acids

“…To examine the physiological response of ants to the various diets, we measured their lipid storage. Some species of ants respond to high-protein diets by increasing their lipid reserves as a possible strategy to survive sugar scarcity [17,18] and others, as observed here in the Argentine ant, see their lipid reserves decrease [19,41,42]. In our experiment, ants collected less free amino acid than whole protein diet, but they presented on average a higher body mass proportion of lipids than those feeding on whole proteins.…”

“…Like many other organisms, ant workers die prematurely on high-protein diets [6, [16][17][18][19]. To find out why, we first focused on the potential toxicity of protein digestion.…”

“…The protein content of the 'whole protein diets' consisted of a mixture of casein, whey powder and white egg proteins as in [6,18,19]. The 'free amino acid diet' contained the same amount of each amino acid as found in the whole protein diet, but in the form of free amino acids instead of whole proteins.…”

Validation of Body Condition Indices and Quantitative Magnetic Resonance in Estimating Body Composition in a Small Lizard

“…Body composition has strong ecological implications. For example, the level of stored fat can influence reproductive output (Bonnet et al., 2001; Milenkaya et al., ), and affect an individual's likelihood of survival under certain environments (e.g., food shortages or nutrient imbalances; Dussutour et al., ) or during critical events (e.g., migration, Sandberg and Moore, ). Body water mass could also be important for survival in arid environments or during periods of drought (Hillman and Gorman, ).…”

Social nutrition: an emerging field in insect science

“…At the most basic level, animals may attract each other to feeding sites, potentially leading to collective foraging dynamics for nutrient balancing [21]. However more complex interactions may occur, as for instance in provisioning species, when adults must simultaneously choose foods to address their nutritional needs as well as the different needs of their offspring [22].…”