JCJC SVSE 7 - JCJC - SVSE 7 - Biodiversité, évolution, écologie et agronomie

Communal nutrition in ants – NUTRIANTS

Communal nutrition in ants

The proposed project on nutrition and social organization in ants addresses a question that has long been recognized, but rarely studied: how are the collective nutritional needs of a colony regulated through the actions of their individual members

Role of nutrition in sociality, division of labour, caste determination and aging.

The proposed work on nutrition and social organization in ants addresses a question that has long been recognized, but rarely studied: how are the collective nutritional needs of a colony regulated through the actions of their individual members? The main strength of the proposal is the rigorous study at the collective level of phenomena previously examined only at the individual level to understand emergence of sociality

A common approach in nutritional studies is to assume, for simplicity, that one environmental factor, such as the energy, protein or the toxin content of foods, and one animal attribute, for example intake rate or food choice, dominates in the relationship between animals and their nutritional environment. In many cases, however, important questions about animal nutrition can only be answered using an integrative approach, which takes into account several attributes of the environment and of the animal, and enables the researcher to study the interactions among these components. The Geometric Framework has been successfully been applied to study nutrient regulation in other animals, including chickens , rats, mice, fish, monkeys and humans and has helped to answer a range of important questions in nutritional biology, from the relationships between nutrition, ageing and reproduction, to the vulnerability of humans to obesity.

Using the geometric framework we were able to demonstrate that the key determinant of the relationship between diet and longevity in ants is the balance of protein to non-protein energy ingested. Lifespan was reduced when ants were fed with high-protein, low-carbohydrate diets.

As we have shown in a study we just completed, eating excess protein relative to non-protein energy shortens lifespan in ants. However it remains unclear how high protein diets increase mortality rates. We will first investigate if the result obtain previously is not simply due to a difficulty for ants to digest protein. Ants are known to possess low level of protease. We will then design a diet with the same ratio of protein to carbohydrates but using amino-acids instead of protein. If as we expect, mortality rate remain unchanged using amino acids we will then investigate other mechanisms to account for this lethal effect of eating excess of protein

Dussutour A. and Simpson S. J 2012 «Ant workers die young and colonies collapse when fed a high-protein diet« Proceedings of the Royal Society London B 279, 2402-2408

So far, most of the researchers have viewed the world of nutrition from the perspective of individual animals. But individuals interact with one another - in family groups, aggregations, swarms and societies - and many of these interactions involve nutrition. Animal groups often appear to act as if they possess a single mind. Whereas it might appear that such groups have collective intelligence, we now know that complex, coordinated behavioural patterns can arise from simple local interactions between individuals. By individuals interacting locally with no knowledge of the behaviour of others except their close neighbours, a group can switch in an instant from disorder to order, or between one collective pattern and another. Subtle changes in the ways in which individuals interact can therefore have profound effects at the collective level, but can an individual’s nutritional state influence how a group behaves? We are beginning to appreciate that the answer to this question is yes.
A major challenge for any animal is maintaining an appropriate amount and balance of nutrients ingested to meet requirements in the face of a nutritionally heterogeneous environment and changing demands of growth, development and reproduction. Extensive studies on non-social insects have elucidated the nutritional regulatory strategies and mechanisms employed by a range of insects and other animals. Animals have been shown to possess separate appetites for protein and carbohydrate, which underlie an ability to compensate for changes in nutrient density in foods and to select among nutritionally complementary foods to achieve a nutritional ‘intake target’. A fundamental question that remains in nutritional biology is how distributed systems maintain an optimal supply of multiple nutrients essential for life and reproduction. We will address this question using highly organised societies of ants in which food for the whole colony is collected by a minority of workers. More broadly, our project will provide an example of how nutrient-specific interactions between individuals can lead to complex collective behaviours.
Being an ant adds a level of complexity to nutritional regulatory strategies. Contrary to other insects, the food entering a social insect colony is assessed and collected by only a small number of its workers. These foragers need to adjust their harvesting strategy to the internal demands for nutrients within the nest, where larvae and workers have different needs. Numerous studies have shown that the distribution of food among the individuals of the colony depends upon the type of nutrient collected, with carbohydrates used mostly by the workers and proteins mainly consumed by the larvae. Consequently, nutritional feedbacks emanating from brood and workers must exist and somehow be integrated to determine food-source exploitation by foragers some of whom may be specialized for the collection of particular nutritional resources. Discovering the mechanisms that social insects use to balance nutrient acquisition and storage is necessary for understanding the allocation of colony foraging labour and the ecological impacts of social insect foraging. However, how social insects such as ants maintain nutrient supply at both a collective and an individual level remain virtually unknown. In this project, we propose to study the importance of nutrition in sociality, division of labour, caste determination and aging.

Project coordination

Audrey DUSSUTOUR (CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE MIDI-PYRENEES) – dussutou@cict.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CNRS/CRCA CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE MIDI-PYRENEES

Help of the ANR 239,975 euros
Beginning and duration of the scientific project: December 2011 - 48 Months

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