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.
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.
Kreider, J.J., Janzen, T., Bernadou, A. et al.
Resource sharing is sufficient for the emergence of division of labour.
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. (doi.org/10.1038/s41567-022-01769-8). (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.
Acceptance and avoidance can be socially transmitted, especially in the case of mate choice.
In Drosophila melanogaster, when afemale 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.
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.
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.
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.
For the past 30 years, agrochemicals have been identified as important causes of pollinator decline. However, the impacts of other equally widespread pollutants, such as heavy metals, have received much less attention. These metal compounds occur naturally in the environment, but their use in industry, agriculture, and domestic applications has significantly elevated their concentrations in soil, water, air, and plants. Lead is of particular concern on a global scale and raises many public health issues related to lead poisoning and certain cancers. Despite the ubiquity of heavy metals in the environment, little or nothing is known about their effects on pollinating insects.
To test these potential effects, the researchers fed hives of honeybees nectar containing lead at low concentrations (below the European regulatory thresholds for the environment) for 10 weeks.
For the first time, Matthias Durrieu, Antoine Wystrach, Patrick Arrufat, Martin Giurfa and Guillaume Isabel from the CRCA have just experimentally showed that fruit flies can solve a more complex learning task.
This study was recently published in the scientific journal Proceedings of the Royal Society B.
Matthias Durrieu, Antoine Wystrach, Patrick Arrufat, Martin Giurfa and Guillaume Isabel
What happens in an animal’s head when it moves? How does it look for food, sexual partners or a migration site? Does it plan its route or does it move randomly? Ethologists from the Centre de Recherche sur la Cognition Animale de Toulouse (CRCA-CBI / CNRS / Université Toulouse III Paul Sabatier) have joined forces with ecologists from the Laboratoire Évolution et Diversité Biologique de Toulouse (EDB – CNRS / Université Toulouse III Paul Sabatier / IRD), Researchers from the École Nationale Vétérinaire de Toulouse (ENVT), together with a company specialising in radio-tracking tools (Xerius), have developed a new methodology within everyone’s reach, based on network analysis, in order to simplify and characterise animal movements in space and time. This new study was published in the journal Methods in Ecology and Evolution.
The multiplication of automated tracking tools now makes it possible to easily obtain high-resolution movement data for a large number of animal species. At the most basic level, it is possible to visualize the sequence of animal positions by joining them by a line, i.e. plotting the animal’s trajectory. Speed, the distance travelled between two successive positions, the time spent in a specific position and changes in direction are some of the main parameters that can be extracted from this trajectory. Variation in these parameters tends to be correlated with changes in an individual’s behaviour. However, until now, these variations have provided little information on the time dimension of trajectories.