Nutrional ecology in social insects

Most living organisms must regulate their nutrient intake to survive and reproduce. This regulation is challenging because animals must manage the fluctuating demands of their own metabolism within the context of nutritionally heterogeneous environments. For social insects, the survival of the group relies on the efforts of only a small number of individual foragers. These foragers do not possess a direct knowledge of the colony’s nutritional state, yet they are able to accurately regulate their intake to meet the varying needs of their nestmates. To further our knowledge of the nutritional ecology of social insects, we need to understand the rules that foragers follow in order to maintain the collective nutrition of the group. Most advances in the field of collective nutrition come from the development of the Nutritional Geometric Framework (NGF). The NGF is a modelling platform that allows the integration of: the animal’s nutritional state, the optimal state it could reach, the foods available and the consequences of eating those foods. The present study combines the use of modelling and experiments implementing the NGF to explore how social insects utilise collective nutrition to fight pathogens and how specialist feeders meet their nutritional needs. Solitary species have been shown to alter their intake of nutrients to fight infections, but how would such a response be achievable on a collective scale? We adapted an existing individual based model of nutrition to investigate the impact of collective nutrient balancing on pathogen spread in a social insect colony. In our model, foragers not only altered their food collection according to their own infection status but also to the status of nestmates, and this social immunity strategy was highly beneficial to the colony when immune responses were short lived. Impaired foraging in infected workers favoured colony resilience when pathogen transmission rate was low (by reducing contact between colony members), or triggered colony collapse when transmission rates were fast (by depleting the pool of foragers). Our findings therefore suggest a new mechanism by which colonies could defend themselves against pathogens and provide a conceptual framework for experimental investigations of the nutritional immunology of social animals. For the rest of my PhD, we investigated the regulation of nutrition in groups of specialist feeders. We developed artificial diets and experimental setups to run the first NGF study on termite macronutrient regulation. We confined termite groups to single diets with varying macronutrient compositions. Diet composition did not affect food intake, but impacted lifespan and foraging. This finding is in direct contrast observation of generalist insects studied thus far. The amount of carbohydrate eaten had a strong effect on lifespan, and foraging activity increased with global intake. We subsequently offered termites various food pairing with highly different protein:carbohydrate ratios. Foragers collected the same amount of food, regardless of protein type or group caste composition. These results validate a nutritional ecology theory predicting that animals specialised on an invariant food type would lose the ability to regulate nutrient composition and would instead only regulate the amount of food collected.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 201

What is really social about social insect cognition?

It is often assumed that social life imposes specific cognitive demands for animals to communicate, cooperate and compete, ultimately requiring larger brains. The “social brain” hypothesis is supported by data in primates and some other vertebrates, but doubts have been raised over its applicability to other taxa, and in particular insects. Here, we review recent advances in insect cognition research and ask whether we can identify cognitive capacities that are specific to social species. One difficulty involved in testing the social brain hypothesis in insects is that many of the model species used in cognition studies are highly social (eusocial), and comparatively little work has been done in insects that live in less integrated social structures or that are solitary. As more species are studied, it is becoming clear that insects share a rich cognitive repertoire and that these abilities are not directly related to their level of social complexity. Moreover, some of the cognitive mechanisms involved in many social interactions may not differ from those involved in non-social behaviors. We discuss the need for a more comparative and neurobiologically grounded research agenda to better understand the evolution of insect brains and cognition

Archéologie du christianisme éthiopien : quinze ans de collaboration scientifique entre le Centre français d’études éthiopiennes et l’Inrap

Depuis une quinzaine d’années, des recherches archéologiques conduites sous l’égide du Centre français d’études éthiopiennes (Cfee) ont contribué à revisiter le christianisme éthiopien et son contexte géographique et historique. De nombreux archéologues de l’Afan puis de l’Inrap ont participé à ces recherches, qui sont désormais inscrites dans le cadre d’un partenariat scientifique. D’autres collaborations ont également été mises en place au cours des dernières années, notamment au sujet de l..

Male attractiveness is subjective to exposure to males of different attractiveness in fruit flies

Abstract Mate choice is a crucial decision in any animal. In terms of fitness, the best mate is the one that leads to the most abundant and productive offspring. Pairing with a low-quality mate would reduce fitness, generating selection for accurate and subtle mate choice in all animal species. Hence, mate choice is expected to be highly context dependent, and should depend on other potential options. For instance, a medium-quality male can constitute the best option when all other males are in poorer condition, but not when there are better-quality males available. Therefore, animals are predicted to gather information about their social context and adapt their mate choice to it. Here, we report on experiments in which we manipulated the social environment of females of Drosophila melanogaster and found that after encountering a high or a low-quality male, they take more or less time to accept copulation with another male, suggesting that females adapt their mating strategy to their social context. We also report on a similar effect in D. biarmiceps. Thus, male attractiveness appears to depend on the quality of recently met males, suggesting that male attractiveness is subjective, indicating plastic and context dependent mate choice

Regulation of macronutrient intake in termites: A dietary self-selection experiment

International audienceMany animals have been shown to select among nutritionally complementary foods to reach a specific balance of nutrients that optimizes key life history traits. Nutritional ecology theory, however, predicts that an animal with a diet that is very stable in its composition, and with nutritional requirements that do not vary in their balance through time, would not need to display such mechanisms of regulation. Here we use the Australian termite Nasutitermes exitiosus as a model to test this prediction for the first time. We used the nutritional geometric framework to investigate the regulation of carbohydrate and protein, as well as the effects on foraging behaviour of protein type and group caste composition and size. Our results support the prediction of nutritional ecology, as termites failed to actively defend a well-defined macronutrient ratio. Termites maintained food collection relatively constant across protein type and group composition, and only appear to vary their collection by avoiding diets too rich in protein

Table_1_What is really social about social insect cognition?.XLSX

It is often assumed that social life imposes specific cognitive demands for animals to communicate, cooperate and compete, ultimately requiring larger brains. The “social brain” hypothesis is supported by data in primates and some other vertebrates, but doubts have been raised over its applicability to other taxa, and in particular insects. Here, we review recent advances in insect cognition research and ask whether we can identify cognitive capacities that are specific to social species. One difficulty involved in testing the social brain hypothesis in insects is that many of the model species used in cognition studies are highly social (eusocial), and comparatively little work has been done in insects that live in less integrated social structures or that are solitary. As more species are studied, it is becoming clear that insects share a rich cognitive repertoire and that these abilities are not directly related to their level of social complexity. Moreover, some of the cognitive mechanisms involved in many social interactions may not differ from those involved in non-social behaviors. We discuss the need for a more comparative and neurobiologically grounded research agenda to better understand the evolution of insect brains and cognition.</p

Archéologie du christianisme éthiopien : quinze ans de collaboration scientifique entre le Centre français d'études éthiopiennes et l'Inrap

National audienc

Tunnelling

Tunnelling activity for each nest, measured every 6 days

Data from: Nutrition in extreme food specialists: an illustration using termites

1. Recent nutritional ecology theories predict that an organism feeding on a single, highly predictable food should lack the typical active regulation of nutrient balance observed in all other organisms studied so far. It could instead limit itself to controlling the amount of food eaten alone. Such an animal would however be strongly affected by nutrient imbalances. 2. Termites are an ideal model animal to test those predictions. 3. We investigated how the nutritional content of food affected termites’ intake and performance by constraining groups of Nasutitermes exitiosus to artificial diets varying in their macronutrient ratios. 4. We showed that (1) termites, contrary to other insects, did not compensate for nutrient imbalance by adjusting food collection (2) longevity in workers was strongly influenced by carbohydrate intake, while in soldiers it depended almost entirely on the number of workers remaining to feed them (3) tunnelling activity increased with the quantity of food collected and (4) intake had very little influence on lipid and protein termite body contents. 5. We provide evidence that extreme food specialists might have lost the ability to regulate macronutrient intake

Ant survival according to the protein type and protein to carbohydrate ratio.

<p>N = 8 experimental colonies of 200 individuals per treatment. Mortality dynamics were consistent between colonies of the same treatment. The dotted lines represent the confidence intervals.</p