12 research outputs found
Group Living Enhances Individual Resources Discrimination: The Use of Public Information by Cockroaches to Assess Shelter Quality
In group-living organisms, consensual decision of site selection results from the interplay between individual responses to site characteristics and to group-members. Individuals independently gather personal information by exploring their environment. Through social interaction, the presence of others provides public information that could be used by individuals and modulates the individual probability of joining/leaving a site. The way that individual's information processing and the network of interactions influence the dynamics of public information (depending on population size) that in turn affect discrimination in site quality is a central question. Using binary choice between sheltering sites of different quality, we demonstrate that cockroaches in group dramatically outperform the problem-solving ability of single individual. Such use of public information allows animals to discriminate between alternatives whereas isolated individuals are ineffective (i.e. the personal discrimination efficiency is weak). Our theoretical results, obtained from a mathematical model based on behavioral rules derived from experiments, highlight that the collective discrimination emerges from competing amplification processes relying on the modulation of the individual sheltering time without shelters comparison and communication modulation. Finally, we well demonstrated here the adaptive value of such decision algorithm. Without any behavioral change, the system is able to shift to a more effective strategy when alternatives are present: the modification of the spatio-temporal distributions of individuals leading to the collective selection of the best resource. This collective discrimination implying such parsimonious and widespread mechanism must be shared by many group living-species
De l'individuel au collectif: dynamiques d'agrégation et choix collectifs chez un arthropode grégaire, la blatte Periplaneta americana
En milieu naturel, la vie en sociĂ©tĂ© implique que de nombreuses actions, activitĂ©s ou dĂ©cisions soient rĂ©alisĂ©es en groupe. Dans la littĂ©rature, nous retrouvons un certain nombre de dĂ©finitions concernant ces dĂ©cisions collectives, mais trĂšs peu de travaux se sont intĂ©ressĂ©s aux mĂ©canismes gouvernant l'apparition de ces formes de coopĂ©ration. En particulier, l'Ă©tude d'espĂšces dâarthropodes sociaux ou grĂ©gaires a Ă©tĂ© dĂ©laissĂ©e au profit des espĂšces eusociales et des groupes de vertĂ©brĂ©s. Ce travail de thĂšse repose sur un ensemble d'expĂ©riences et de modĂ©lisations destinĂ©es Ă approfondir notre comprĂ©hension des mĂ©canismes gouvernant les dĂ©cisions collectives chez les insectes grĂ©gaires. Pour mener Ă bien ce travail, nous avons quantifiĂ© les rĂ©ponses individuelles et collectives chez la blatte Periplaneta americana, dans un milieu caractĂ©risĂ© par la prĂ©sence de sites de repos (de qualitĂ© identique ou diffĂ©rente). Il s'agit de comprendre et de caractĂ©riser les diffĂ©rentes dynamiques qui, sur base des prĂ©fĂ©rences individuelles pour les diffĂ©rents sites de repos et des interactions sociales, permettent Ă l'Ă©chelle de la population l'Ă©mergence dâun choix collectif, et au niveau individuel, Ă lâexploitation optimale de son environnement. Nos rĂ©sultats ont montrĂ© que malgrĂ© l'absence de communication ou de perception Ă longue distance (ex :orientation visuelle, phĂ©nomĂšnes de suivi de piste), sans comparaison ni connaissance parfaite du milieu (ex :la localisation et le nombre dâabris ou de congĂ©nĂšres) les blattes sont capables de discriminer collectivement entre des alternatives spatialement dispersĂ©es et de faire le meilleur choix (associĂ© au maintien de la cohĂ©sion). Ce phĂ©nomĂšne de choix collectif est un sous-produit des diffĂ©rentes dynamiques agrĂ©gatives gouvernĂ©es par les compĂ©titions entre processus dâamplification et permet au groupe de rĂ©soudre un problĂšme qui est au-dessus des capacitĂ©s individuelles. Dans nos expĂ©riences, cela se manifeste par une double augmentation en fonction de la taille du groupe: (1) un individu tend Ă s'installer plus souvent dans un site de repos et (2) un individu a plus de chances de se retrouver sous le site de repos optimal. Une analyse plus fine des comportements individuels, rendue possible par l'utilisation de la RFID, a montrĂ© quâau sein des blattes, deux stratĂ©gies existaient: les initiateurs et les explorateurs. Enfin, l'utilisation de robots (sociĂ©tĂ©s mixtes blattes/robots) nous a permis de valider notre modĂšle thĂ©orique mais aussi dâintroduire artificiellement des conflits d'intĂ©rĂȘt entre les membres du groupes :la prĂ©sence de ces individus clefs peut modifier la rĂ©ponse collective de maniĂšre dramatique.AprĂšs avoir comparĂ© nos travaux avec la littĂ©rature actuelle, nous avons discutĂ© de la valeur gĂ©nĂ©rique de tels processus agrĂ©gatifs, prĂ©requis essentiel pour la coordination et la synchronisation des activitĂ©s des individus. L'agrĂ©gation constitue une des conditions nĂ©cessaires et indispensables Ă l'apparition dâune vie sociale permettant le dĂ©veloppement dâune coopĂ©ration plus Ă©laborĂ©e.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe
Weak individual preference versus strong collective sensitivity:a density-dependent process
info:eu-repo/semantics/nonPublishe
Self-amplification as a source of interindividual variability: Shelter selection in cockroaches
Although group effect and collective decisions have been described in many insect species, the behavioral mechanisms involved in the process remain poorly documented at the individual level. We examined how individual behavior depends on the environmental context and we precisely characterized the behavioral rules leading to settlement of individual cockroaches in resting site. We focused on the spatial and temporal distribution of individuals in absence of conspecifics. Using isolated adult males of the cockroach Periplaneta americana, we showed that the quality of resting sites and the duration of the settlement exerted an influence on the individual decision-making: the probability of leaving a resting site decreased with the time spent under a shelter. A numerical model derived from experimental data suggested that this simple rule of self-amplification can also account for the interindividual variability.info:eu-repo/semantics/publishe
Collective decision and interindividual variability in cockroaches
info:eu-repo/semantics/nonPublishe
Dynamic of sheltering behavior.
<p>Change over time (min) of the mean fraction of cockroaches under shelters for groups confronted with a choice between 1 (nâ=â16, triangles), 2 (nâ=â21, diamonds), 6 (nâ=â21, squares), or 10 identical shelters (nâ=â32, circles).</p
Surface and diameter of the shelters for the 4 experimental conditions.
<p>Surface and diameter of the shelters for the 4 experimental conditions.</p
Theoretical and experimental spatial distribution.
<p>Frequency distribution of the cluster size at tâ=â480 minutes for (a) F2, (b) F6, and (c) F10. Histogram: experimental distribution. Solid line: theoretical distribution generated by our model (eq.1). Dashed line: binomial distribution with random behavior. Parameters values: ÎŒâ=â0.0007, Ξâ=â0.0049, nâ=â2.5, kâ=â4, Ïâ=â1296.</p
Theoretical and experimental influence of fragmentation on the sheltering behavior.
<p>Mean fraction of the total population under shelters (± S.D.) at tâ=â480 minutes for F1, F2, F6, and F10. Comparison of the experimental (black) and theoretical (white) data. Parameters values: ÎŒâ=â0.0007, Ξâ=â0.0049, nâ=â2.5, kâ=â4, Ïâ=â1296.</p
Lipids containing medium-chain fatty acids are specific to post-whole genome duplication Saccharomycotina yeasts
Background: Yeasts belonging to the subphylum Saccharomycotina have been used for centuries in food processing and, more recently, biotechnology. Over the past few decades, these yeasts have also been studied in the interest of their potential to produce oil to replace fossil resources. Developing yeasts for massive oil production requires increasing yield and modifying the profiles of the fatty acids contained in the oil to satisfy specific technical requirements. For example, derivatives of medium-chain fatty acids (MCFAs, containing 6-14 carbons) are used for the production of biodiesels, cleaning products, lubricants and cosmetics. Few studies are available in the literature on the production of MCFAs in yeasts. Results: We analyzed the MCFA content in Saccharomyces cerevisiae grown in various conditions. The results revealed that MCFAs preferentially accumulated when cells were grown on synthetic media with a high C/N ratio at low temperature (23 degrees C). Upon screening deletion mutant strains for genes encoding lipid droplet-associated proteins, we found two genes, LOA1 and TGL3, involved in MCFA homeostasis. A phylogenetic analysis on 16 Saccharomycotina species showed that fatty acid profiles differed drastically among yeasts. Interestingly, MCFAs are only present in post-whole genome duplication yeast species. Conclusions: In this study, we produced original data on fatty acid diversity in yeasts. We demonstrated that yeasts are amenable to genetic and metabolic engineering to increase their MCFA production. Furthermore, we revealed that yeast lipid biodiversity has not been fully explored, but that yeasts likely harbor as-yet-undiscovered strains or enzymes that can contribute to the production of high-value fatty acids for green chemistry