Communal Nutrition in Ants

School of Biological Sciences and Centre for Mathematical Biology, The University of Sydney, NSW 2006, Australia.
Current biology: CB (Impact Factor: 9.57). 05/2009; 19(9):740-4. DOI: 10.1016/j.cub.2009.03.015
Source: PubMed


Studies on nonsocial insects have elucidated the regulatory strategies employed to meet nutritional demands [1-3]. However, how social insects maintain the supply of an appropriate balance of nutrients at both a collective and an individual level remains unknown. Sociality complicates nutritional regulatory strategies [4-6]. First, the food entering a colony is collected by a small number of workers, which need to adjust their harvesting strategy to the demands for nutrients among individuals within the colony [4-7]. Second, because carbohydrates are used by the workers and proteins consumed by the larvae [7-14], nutritional feedbacks emanating from both must exist and be integrated to determine food exploitation by foragers [4-6, 15, 16]. Here, we show that foraging ants can solve nutritional challenges for the colony by making intricate adjustments to their feeding behavior and nutrient processing, acting both as a collective mouth and gut. The amount and balance of nutrients collected and the precision of regulation depend on the presence of larvae in the colony. Ants improved the macronutrient balance of collected foods by extracting carbohydrates and ejecting proteins. Nevertheless, processing excess protein shortened life span--an effect that was greatly ameliorated in the presence of larvae.

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Available from: Audrey Dussutour
    • "When restricted to a single nutritionally imbalanced diet, food intake is driven essentially by carbohydrate, increasing as the percentage of carbohydrate in the diet decreases (Dussutour & Simpson, 2009). Therefore, when ants are on a highproteinelow-carbohydrate diet, they compensate for the shortage of carbohydrate by drastically increasing their food intake to meet their carbohydrate requirements (Dussutour & Simpson, 2009, 2012). However, this compensation comes at a cost: when ants consume a higher proportion of protein than required, mortality is higher, as observed in many other insects (Hamilton, Cooper, & Schal, 1990; Lee et al., 2008; Maklakov et al., 2008; Pirk, Boodhoo, Human, & Nicolson, 2010). "
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    ABSTRACT: In social insects, food collection for the entire colony relies on a minority of its workers. How can the colony choose between resources, determine the task allocation of workers and exhibit a flexible food storage strategy from the foraging decisions taken only by a minority? We addressed this question by posing nutritional challenges to trap-jaw ants, Odontomachus hastatus, and explored their response in terms of survival, foraging behaviour and energy storage. In the first challenge, ants alternated between long periods of confinement to a high-protein diet and short periods of confinement to a high-carbohydrate diet. In the second challenge, ants alternated between long periods of confinement to a high-carbohydrate diet and short periods of confinement to a high-protein diet. In the third challenge, ants were given simultaneously a high protein and high-carbohydrate diet. First, we showed that (1) mortality increased with protein consumption, (2) a brief exposure to a high-carbohydrate diet lessened the negative consequence of high protein consumption and (3) ants given a choice of complementary diets regulated intake and minimized mortality. We also demonstrated that ants used an energy-saving strategy to overcome challenging nutritional environments. In addition we showed that the ants had an extraordinary capacity to regulate the amounts of food entering the nest both at the collective level by allocating more workers to foraging on a high-protein diet and at the individual level by collecting more food on a high-carbohydrate diet. Our study provides new insights into the strategies used by ants facing nutritional challenges and deepens our understanding of the nutritional ecology of ants and, thereby, their vast ecological success.
    No preview · Article · Jan 2016 · Animal Behaviour
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    • "The latter is particularly important when parents and offspring have disparate nutritional needs (e.g., Fewell and Winston 1992), forcing parents to apportion their foraging effort between resources for themselves versus their offspring. Behavioral mechanisms for coping with variation in need include separate foraging trips for self-versus offspring-optimal resources (e.g., Welcker et al. 2009), or foraging proportionately more for offspring as their demand increases (e.g., Eckert et al. 1994; Dussutour and Simpson 2009). Faced both with the need to collect multiple resources and to feed offspring, 2 major questions arise: 1) what resource(s) (and how much of each resource) should organisms collect during a foraging bout? "
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    ABSTRACT: How foragers cope with complexity in both needs and resources is a major question in behavioral ecology. When faced with nutritionally diverse resources, or when foraging for offspring with divergent nutritional needs, animals must meet the challenge of how to structure their foraging bouts, including what resources to forage for and in what order (how) to collect them. We investigated how nutritional variation in resources and requirements shapes the structure of bumble bee foraging bouts. Bumble bee workers collect 2 nutritionally distinct resources for consumers with different nutritional needs, floral nectar (largely carbohydrates) for their own needs and that of larvae, and pollen (largely protein) that is used primarily by larvae. We maintained colonies of the Eastern Bumble Bee (Bombus impatiens) in the laboratory on either protein-rich or protein-limited diets and assessed bees’ foraging bout structure on artificial flowers that offered low, medium, or high ratios of pollen to nectar. We analyzed bout structure using both traditional floral constancy metrics as well as hierarchical Bayesian analyses. Bees from pollen-satiated colonies responded to variation in floral pollen:nectar ratios, tending to collect pollen consecutively when nectar volumes were high. In contrast, foragers from pollen-limited colonies were relatively insensitive to floral reward ratio, tending to collect pollen in long runs regardless of nectar volume. We discuss the implications of these findings for the pollination services that bees provide plants.
    Full-text · Article · Jan 2016 · Behavioral Ecology
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    • "Many animals also live in groups or populations that simultaneously contain individuals of differing developmental stages, and there is abundant evidence that nutritional requirements change throughout an individual's life cycle (Raubenheimer et al. 2007; Simpson and Raubenheimer 2012). Social insects such as ants, for example, live in colonies with overlapping generations, where optimal diets range from the protein-rich diet needed by growing larvae to the carbohydrate-rich diet eaten by nonreproductive adults for colony maintenance (Dussutour and Simpson 2009). Finally , even where individuals appear the same sex and age, heterogeneity in many other traits that may correlate with nutritional requirements is readily observable; examples include between-individual variation in metabolic rate, body size, and life-history strategy (Cam et al. 2002; Honěk 1993; Huchard et al. 2014; Lim et al. 2014; Mathot and Dingemanse 2015). "
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    ABSTRACT: The determinants of diet breadth are of interest to nutritionists, ecologists, and evolutionary biologists. A recent synthesis addressing this issue found conflicting evidence for the relationship between diet breadth and mean individual fitness. Specifically, it found that while, on average, a mixed diet does increase mean fitness, in some instances, a single food provides equal (or higher) fitness than a mixed diet. Critical to ecological and evolutionary considerations of diet, however, is not only mean fitness but also variance in fitness. We combine contemporary meta-analytic methods with models of nutritional geometry to evaluate how diet affects between-individual variance in fitness within generalist consumers from a range of trophic levels. As predicted by nutritional geometry, we found that between-individual variance in fitness-related traits is higher on single-food than mixed diets. The effect was strong for longevity traits (57% higher) and reproductive traits (37%) and present but weaker for size-related traits (10%). Further, the effect became stronger as the number of available foods increased. The availability of multiple foods likely allows individuals with differing nutritional optima to customize intake, each maximizing their own fitness. Importantly, these findings may suggest that selection on traits correlated with nutritional requirements is weak in heterogeneous nutritional environments.
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