Collective self-medication in ants.

Nutrition is a major factor influencing host-parasite interactions. Animals can fight parasites by modifying their food choices to strengthen their immune systems and the parasites, on the other hand, can manipulate their host's foraging behavior to obtain the nutrients they need to thrive.

In this study, Eniko Csata, Alfonso Pérez-Escudero, Emmanuel Laury, Gérard Latil and Audrey Dussutour (CRCA-CBI) and their collaborators studied the role of nutrition in the host-parasite system: the Argentine ant (Linepithema humile) and the entomopathogenic fungus (Metarhizium brunneum), and revealed that the modification of food choices observed in ants infected by a fungus is not dictated by the parasite, but by a form of collective self-medication.

Read the CNRS Biology press release :

Champignon sur le régime optimal riche en acides aminés (en haut à gauche), fourmis non infectées choisissant un régime riche en sucre (en haut à droite), fourmis infectées choisissant le régime optimal du champignon riche en acides aminés (au centre), fourmi injectée avec des cellules de champignon inerte (en bas à droite).

Reference :

Csata E, Pérez-Escudero A, Laury E, Leitner H, Latil G, Heinze J, Simpson SJ, Cremer S, DussutourA.

Fungal infection alters collective nutritional intake of ant colonies

Current Biology. :February 01, 2024. DOI:


 Contact : Audrey Dussutour

How digital traces promote cooperation or deception in human groups?

Over the past thirty years, the digitization of society has profoundly changed people's ways of life and communication. The information exchanged between individuals is increasingly taking the form of digital traces that are widely exploited by social networks and online commerce on the Internet, in particular through the use of rating and recommendation systems which allow users to discover new options or guide their choices.

Researchers from the Research Center on Animal Cognition, the Theoretical Physics Lab and the Toulouse School of Economics have studied how and under what conditions digital traces could allow groups of individuals to cooperate in an information search task and how reliable was the information imbedded in these traces. The researchers have analyzed and modeled the tagging behaviors of individuals and the way theyr use of digital traces thanks to a dedicated interactive web application integrating a rating system similar to that used by many e-commerce platforms.

The results published in PNAS show that groups of individuals can spontaneously and without any prior comunication between them use the fingerprints resulting from their notations to coordinate their search and collectively find the cells with the highest values in a table of hidden numbers. However, this study has also revealed that in competitive situations, the use of digital traces promotes deception because a large proportion of individuals then reduces the reliability of the information contained in the traces they leave.

Read the CNRS press release

Figures 1 & 2. Experimental setup consisting of a computer network used to study the impact of digital traces on collective information search behavior in human groups.

Figures 3 & 4. Interactive web application used by participants during the experiment. This application allows groups of subjects to independently explore the same table of numbers through a graphical interface and to interact indirectly with each other through the color traces that result from their actions.


Bassanetti, T., Escobedo, R., Cezera, S., Blanchet, A., Sire, C. & Theraulaz, G.

Cooperation and deception through stigmergic interactions in human groups.

Proceedings of The National Academy of Sciences USA

October 10, 2023, 120 (42) e2307880120,



  • Pour l’Institut des Sciences Biologiques :

Guy Theraulaz

Centre de Recherches sur la Cognition Animale (CRCA), Centre de Biologie Intégrative (CBI)

& Institute for Advanced Study in Toulouse (IAST)

Centre National de la Recherche Scientifique (CNRS)

Université de Toulouse (Paul Sabatier)

31062 Toulouse, France

  • Pour l’Institut de Physique :

Clément Sire

Laboratoire de Physique Théorique

Centre National de la Recherche Scientifique (CNRS)

Université de Toulouse (Paul Sabatier)

31062 Toulouse, France


Social tolerance can be restored in aggressive spiders after molting.

In many taxa, the subsocial route is considered the main pathway to permanent sociality, but the relative contribution of offspring interactions and parental care to the maintenance of cohesion and tolerance at advanced developmental stages remains poorly studied.

Spiders are relevant models for this question because they all show a transient gregarious phase before dispersal, and the transition to permanent sociality, which concerns approximately 20 of the ∼50,000 species, is assumed to rely on the subsocial route.

Using spiderlings of the solitary species Agelena labyrinthica, we manipulated the social context to demonstrate that tolerance in aggressive juveniles can be restored when exposed to siblings after moulting. We propose that moulting can reopen closed critical periods and renew the imprinting to social cues and thus lead to the reacquisition of tolerance. Our study highlights the critical role of contacts between juveniles in the expression of tolerance, which opens novel avenues for understanding social transitions.


Social recapitulation: moulting can restore social tolerance in aggressive spiderlings.

Emilie Mauduit, Raphaël Jeanson

J Exp Biol (2023) 226 (7): jeb245387.




In the blob, aging could be reversible!

© David VILLA / ScienceImage, CBI / CRCA / CNRS

How behaviour changes with correlates of age in unicellular organisms remains an open question.

The main reason for this might be that single-cell organisms were mistakenly believed to be short-lived and immune to ageing.

It has now been demonstrated that some unicellular organisms such as bacteria, paramecia and yeast, undergo intrinsic changes over time that affect their behavior and physiology.

In this study, Audrey Dussutour, Angèle Rolland, Emilie Pasquier, Paul Malvezin, Cassandra Craig and Mathilde Dumas (CRCA-CBI) studied how the behavior of the slime mold Physarum Polycephalum, a unicellular organism, varies over the lifetime of individuals, and they showed that aging in the blob might be partially reversible.

En haut : vitesse de déplacement des blobs en fonction de l’âge. Six groupes de blobs de différents âges (1, 17, 32, 54, 74 et 94 semaines) ont été utilisés pour réaliser cette expérience. Les substrats étaient constitués de gel d’avoine. En bas : Vitesse de déplacement des blobs avant et après la fusion d’un blob âgé et d’un blob jeune. Les substrats étaient constitués de gel d’avoine. © Audrey Dussutour CBI / CNRS


Behavioural changes in slime moulds over time

A. Rolland, E. Pasquier, P. Malvezin, C. Craig, M. Dumas et A. Dussutour

Philosophical Transactions of the Royal Society B le 20 février 2023. DOI:

More information


Audrey Dussutour


Resource sharing is sufficient for the emergence of division of labour

Division of labour occurs in a broad range of organisms. Yet, how division of labour can emerge in the absence of pre-existing interindividual differences is poorly understood.

Using a simple but realistic model, we show that in a group of initially identical individuals, division of labour emerges spontaneously if returning foragers share part of their resources with other group members. In the absence of resource sharing, individuals follow an activity schedule of alternating between foraging and other tasks. If non-foraging individuals are fed by other individuals, their alternating activity schedule becomes interrupted, leading to task specialisation and the emergence of division of labour. Furthermore, nutritional differences between individuals reinforce division of labour. Such differences can be caused by increased metabolic rates during foraging or by dominance interactions during resource sharing.

Our model proposes a plausible mechanism for the self-organised emergence of division of labour in animal groups of initially identical individuals. This mechanism could also play a role for the emergence of division of labour during the major evolutionary transitions to eusociality and multicellularity.

Reference :

Kreider, J.J., Janzen, T., Bernadou, A. et al.

Resource sharing is sufficient for the emergence of division of labour.

Nat Commun 13, 7232 (2022).

Contact :


Moving in a single file

Considering pairs of sheep, in group size 2, 3 and 4, we explore the relevancy of the following interactions: aligning (V), moving toward (simple attraction P) or a combination of both (V+P). Using our experimental date and mathematical simulation, three models of interactions were tested: all can interact with all (IN1); all groups members moving in front of you are possibly influential (IN2); only the closest neighbor in front of you is influential (IN3). In each moving phase, every individual could be a leader until the collective motion stops. We found that the best scenario is the following one: when an individual decide to move and become a leader, most often group members abide by moving in a cascade of departures, toward the group member (V) that precede in the file (IN3).

Figure extacted from the paper in Gómez-Nava, Bon et Peruani. 2022. ( (a) A snapshot of a large group summering In French Alps. (b) One image obtained from a simulation of a group of 40 sheep on the move using the most relevant model. Leader : darked greyed spot and its movement represented by an arrow. (c) Representation of interaction network in a goup of 13 animals, based on the IN3 model. The cascade of influence (arrow) : it propagates down the hierarchical network, individuals being represented by a circle.


Gómez-Nava, L., Bon, R. & Peruani, F.
Intermittent collective motion in sheep results from alternating the role of leader and follower.
Nat. Phys. (2022).


Richard BON

Female fruit flies copy the acceptance, but not the rejection, of a mate

Acceptance and avoidance can be socially transmitted, especially in the case of mate choice.

In Drosophila melanogaster, when a female observes a conspecific female (called demonstrator female) choosing to mate with one of two males, the former female (called observer female) can memorize and copy the latter female’s choice. Traditionally in mate-copying experiments, demonstrations provide two types of information to observer females, namely, the acceptance (positive) of one male and the rejection of the other male (negative).

To disentangle the respective roles of positive and negative information in Drosophila mate copying, we performed experiments in which demonstrations provided only one type of information at a time. We found that positive information alone is sufficient to trigger mate copying. This suggests that Drosophila females learn to prefer the successful males, implying that the underlying learning mechanisms may be shared with those of appetitive memory in non-social associative learning.

Following an observation by a female observer of a female demonstrator copulating with a green but not a pink, this observer copulates with the green male not because she rejects the pink, but because she chooses the green. Photo by David Villa ScienceImage CBI CNRS


Nöbel S., Monier M., Fargeot L., Lespagnol G., Danchin E., Isabel G.

Female fruit flies copy the acceptance, but not the rejection, of a mate.

Behavioral Ecology, 2022 Aug.


Guillaume ISABEL

Insulin modulates emotional behavior through a serotonin-dependent mechanism

In mice, insulin injection reduces the level of anxiety by modulating the activity of this neuronal population. On the contrary, in mice fed a “high fat diet”, serotonin neurons become resistant to insulin and the beneficial behavioural effects of this hormone disappear.

This work offers interesting prospects, in particular the repositioning of oral antidiabetics – which improve insulin sensitivity – in the treatment of anxiety-depressive episodes.

Extrait de la figure 1 de l’article de Martin, Bullich et al., 2022 (doi: 10.1038/s41380-022-01812-3). Identification de la présence du récepteur à l’insuline sur les neurones sérotoninergiques du noyau dorsal du raphé. Images de microscopie confocales représentant les neurones sérotoninergiques en rouges (cellules TPH2 positives) et l’ARNm du récepteur à l’insuline (points verts) détecté par fluorescence après hybridation in situ. Le panel de droite (à fort grossissement) signale le co-marquage (triangles blancs) illustrant la présence du récepteur à l’insuline sur les neurones sérotoninergiques.


Martin H, Bullich S, Martinat M, Chataigner M, Di Miceli M, Simon V, Clark S, Butler J, Schell M, Chopra S, Chaouloff F, Kleinridders A, Cota D, De Deurwaerdere P, Pénicaud L, Layé S, Guiard BP, Fioramonti X
Insulin modulates emotional behavior through a serotonin-dependent mechanism.
Mol Psychiatry. 2022 Oct 7. doi: 10.1038/s41380-022-01812-3




Remodeling the hippocampus for allowing Alzheimer’s mice to remember others

© Laure Verret, CRCA-CBI

The area CA2 of the hippocampus is a brain structure necessary for social memory, a function profoundly impaired in Alzheimer’s disease. This study led by Laure Verret (CRCA-CBI) and collaborators from Toulouse and Paris, published in iScience, shows that mice modeling Alzheimer’s disease are unable to remember a conspecific, and that this is associated with anatomical and functional abnormalities in CA2. However, a single injection of the protein NRG1 into CA2 restores social memory ability of Alzheimer’s mice.

Among the cognitive disorders in Alzheimer’s disease (AD) patients, their inability to remember others, is one of the most excruciating. However, little is known about the neural mechanisms underlying social memory. The hippocampus is a brain structure that is pivotal for memory processes, that is deeply affected in AD. In particular, the inhibitory neurons expressing the parvalbumin protein are known to be dysfunctional in the hippocampus of Alzheimer’s patients, as well as in mouse models of the disease. These neurons, often referred to as “conductors of the orchestra”, play an essential role in organizing the information flow in the brain, and thus in the emergence of complex cognitive functions, such as formation or recall of memories via the hippocampus. Within the hippocampus, the are CA2 appears crucial for the formation of social memory, specifically. This area is very rich in parvalbumin neurons and their extracellular matrix (perineuronal net, PNN). This matrix plays a protective role and ensures the maintenance of synapses on parvalbumin neurons.

In this study, the scientists observed some alterations of CA2 in AD mice that could be involved in social memory deficits. In particular, they revealed that parvalbumin neurons are less present, and that those remaining are less surrounded by PNN, in the CA2 of AD mice. This anatomical disruption is associated with a decrease of the synaptic plasticity that underlies social learning. Subsequently, the scientists conducted tests to evaluate the social behavior of AD mice. They observed that they had normal sociability, i.e., they were just as interested in their peers as healthy mice, but they were unable to remember a mouse with which they had repeatedly interacted within a few minutes ago. In order to establish a link between anatomical and functional perturbations of area CA2 and social memory deficits, the scientists then showed that a specific disruption of PNN in CA2 is sufficient to induce a alteration of social memory in healthy mice. Finally, the scientists sought to restore the presence of parvalbumin neurons and their PNN only in CA2 of AD mice. To do this, they used a protein normally present in the hippocampus during brain maturation. Surprisingly, a single injection of this protein, neuregulin-1 (NRG1), into the CA2 of Alzheimer’s mice induced in 5 days, an increase in parvalbumin neurons and their PNN. This anatomical improvement is associated with a complete recovery of the social memory ability of the AD mice, without improving other types of memory. These neural mechanisms thus revealed in a mouse model of AD could open up avenues for restoring social memory in Alzheimer’s disease.


Altered inhibitory function in hippocampal CA2 contributes in social memory deficits in Alzheimer’s mouse model.
Rey CC, Robert V, Bouisset G, Loisy M, Lopez S, Cattaud V, Lejards C, Piskorowski RA, Rampon C, Chevaleyre V, Verret L.
iScience. 24 février 2022. doi: 10.1016/j.isci.2022.103895.


Laure Verret


CO2, a social cue for memory expression in Drosophila

© David Villa / Guillaume Isabel

In this study published in the journal Current Biology, scientists show that CO2 released by Drosophila flies in a group recruits a long-lasting cryptic memory, which adds to the existing individual memory.

They identify the neural network underlying this CO2-dependent memory and suggest that natural variations in CO2 can modulate cognitive processes in insects.

The animal has the ability to establish associative links between distinct events, or between its own behavior and its direct consequences. Faced with an environment with changing and complex sources of information, the animal can thus rapidly adapt its behavior by integrating its past experiences, thus optimizing the quality of its decision making. Interactions between animals are an important source of information. The contribution of social interactions in the acquisition of new information has thus attracted much attention. However, the influence of the social context on the restitution of previously acquired information is still little known.

Read more


Reference :

Social facilitation of long-lasting memory is mediated by CO2 in Drosophila.

Muria A, Musso PY, Durrieu M, Portugal FR, Ronsin B, Gordon MD, Jeanson R, Isabel G.

Curr Biol. 2021 Mar 12. doi: 10.1016/j.cub.2021.02.044

Contact :

Guillaume ISABEL