HAL Portal UPF (Université de la Polynésie française)
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Substantial gene expression shifts during larval transitions in the pearl oyster Pinctada margaritifera
No full textInternational audienceEarly development stages in marine bivalve are critical periods where larvae transition from pelagic free‐life to sessile mature individuals. The successive metamorphosis requires the expression of key genes, the functions of which might be under high selective pressure, hence understanding larval development represents key knowledge for both fundamental and applied research. Phenotypic larvae development is well known, but the underlying molecular mechanisms such as associated gene expression dynamic and molecular cross‐talks remains poorly described for several nonmodel species, such as P. margaritifera . We designed a whole transcriptome RNA‐sequencing analysis to describe such gene expression dynamics following four larval developmental stages: d ‐shape, Veliger, Umbo and Eye‐spot. Larval gene expression and annotated functions drastically diverge. Metabolic function (gene expression related to lipid, amino acid and carbohydrate use) is highly upregulated in the first development stages, with increasing demand from d ‐shape to umbo. Morphogenesis and larval transition are partly ordered by Thyroid hormones and Wnt signaling. While larvae shells show some similar characteristic to adult shells, the cause of initialization of biomineralization differ from the one found in adults. The present study provides a global overview of Pinctada margaritifera larval stages transitioning through gene expression dynamics, molecular mechanisms and ontogeny of biomineralization, immune system, and sensory perception processes
Leveraging Noisy Observations in Zero-Sum Games
No full textInternational audienceThis paper studies an instance of zero-sum games in which one player (the leader) commits to its opponent (the follower) to choose its actions by sampling a given probability measure (strategy). The actions of the leader are observed by the follower as the output of an arbitrary channel. In response to that, the follower chooses its action based on its current information, that is, the leader's commitment and the corresponding noisy observation of its action. Within this context, the equilibrium of the game with noisy action observability is shown to always exist and the necessary conditions for its uniqueness are identified. Interestingly, the noisy observations have important impact on the cardinality of the follower's set of best responses. Under particular conditions, such a set of best responses is proved to be a singleton almost surely. The proposed model captures any channel noise with a density with respect to the Lebesgue measure. As an example, the case in which the channel is described by a Gaussian probability measure is investigated
Artificial Light Increases Nighttime Prevalence of Predatory Fishes, Altering Community Composition on Coral Reefs
No full textInternational audienceArtificial light at night (ALAN) is an anthropogenic pollutant that is intensifying and expanding in marine environments, but experimental studies of community‐level effects are generally lacking. The inshore, shallow, and clear‐water locations of coral reefs and their diverse photosensitive inhabitants make these ecosystems highly susceptible to biological disturbances; at the same time, their biodiversity and accessibility make them model systems for wider insight. Here, we experimentally manipulated ALAN using underwater LED lights on a Polynesian reef system to investigate the influence on localised nighttime fish communities compared to control sites without ALAN. We collected infrared video censuses of baseline communities prior to manipulation, which we repeated following short‐term (mean of three nights) and prolonged (mean of 25 nights) exposures to ALAN. Short‐term ALAN exposure did not induce any significant alterations to the nighttime fish community, but prolonged ALAN exposure increased nighttime species richness. Species compositions exposed to prolonged ALAN were more dissimilar from their baseline compared to control sites. The difference between community compositions at prolonged ALAN exposure and control sites was not apparent at the family level; instead, it was observed from the composition of trait guilds. Following prolonged ALAN exposure, more diurnal and nocturnal predatory species (piscivores, invertivores, and planktivores)—particularly those that are site‐attached or mobile within reefs—were present in nighttime assemblages. Our experimental findings show that coastal ALAN could cause trophic imbalances and circadian disturbances in localised nighttime reef fish communities. Given that community‐wide consequences were only apparent after prolonged ALAN exposure suggests that management of the duration of artificial lighting could potentially be used to reduce impacts on marine ecosystems
L'agriculture urbaine tahitienne : les jardins collectifs, des tiers lieux entre bienfaits sociaux et sociétaux
No full textInternational audienceA place for socialising and socialising, a community garden is a meeting place where you can extend your social network. The gardens studied have a civic and even political dimension, which means that they can be likened to ‘third places’. As part of the public realm, they are new spaces for leisure, learning, sharing, working together, innovation and entrepreneurship. With the development of community gardens in the Papeete area, this study confirms the importance of links between urban dwellers and these leisure spaces. In the words of the people we met, these gardens represent hybrid places that lie between the public and private spheres, and between collective and individual space.Espace de socialisation et de sociabilisation, un jardin collectif est un lieu de rencontre, permettant d’étendre son réseau social. Ceux étudiés sont assortis d’une dimension d’expression citoyenne, voire politique, qui revient à assimiler les jardins collectifs à des « tiers lieux ». Au sein de l’espace public, ils caractérisent de nouveaux espaces de loisirs, d’apprentissage, de partage, de travail en commun, d’innovation et d’entrepreneuriat. Face au développement des jardins collectifs dans l’agglomération de Papeete, cette étude confirme l’importance des liens entre les urbains et ces espaces de loisirs. Dans les discours des personnes rencontrées, ces jardins représentent des lieux hybrides qui se situent entre la sphère publique et privée, puis entre l’espace collectif et individuel
Jurys de concours : de la difficulté à concilier impartialité et collégialité
No full textInternational audienceNote sous TA Paris, 13 mars 2024, no 222028
Application de la rétroactivité in mitius à la répression disciplinaire : que faire lorsque la loi est plus douce et plus sévère à la fois ?
No full textInternational audienceNote sous CE 5 mars 2024, no 461548 (Lebon T.
Epigenetic then genetic variations underpin rapid adaptation of oyster populations (Crassostrea gigas ) to Pacific Oyster Mortality Syndrome (POMS)
No full textDisease emergence is accelerating in response to human activity-induced global changes. Understanding the mechanisms by which host populations can rapidly adapt to this threat will be crucial for developing future management practices. Pacific Oyster Mortality Syndrome (POMS) imposes a substantial and recurrent selective pressure on oyster populations ( Crassostrea gigas) . Rapid adaptation to this disease may arise through both genetic and epigenetic mechanisms. In this study, we used a combination of whole exome capture of bisulfite-converted DNA, next-generation sequencing, and (epi)genome-wide association mapping, to show that natural oyster populations differentially exposed to POMS displayed signatures of selection both in their genome (single nucleotide polymorphisms) and epigenome (CG-context DNA methylation). Consistent with higher resistance to POMS, the genes targeted by genetic and epigenetic variations were mainly related to host immunity. By combining correlation analyses, DNA methylation quantitative trait loci, and variance partitioning, we revealed that a third of the observed phenotypic variation was explained by interactions between the genetic sequence and epigenetic information, ∼14% by the genetic sequence, and up to 25% by the epigenome alone. Thus, as well as genetic adaptation, epigenetic mechanisms governing immune responses contribute significantly to the rapid adaptation of hosts to emerging infectious diseases
L'obligation de reclassement des agents contractuels territoriaux en cas de suppression d'emploi
No full textInternational audienceNote sous TA Toulon, 10 novembre 2023, no 2201036, Commune de La Seyne-sur-me
Combiner l’approche sociologique et psychométrique pour étudier les performancesscolaires : le cas du calcul mental au Sénégal
No full textInternational audiencePlusieurs études montrent que les représentations sociales associées aux mathématiques ont un impact sur les performances scolaires des élèves dans cette discipline. Ces représentations –en tant que produit d'une culture dominante – émergent au sein d'un écosystème d'apprentissage et dépendent de facteurs socio-économiques : dans certains territoires, elles sont modelées par des préjugés et des stéréotypes hérités du passé colonial, comme dans plusieurs pays d’Afrique. Cet article présente les résultats d'un enquête psychométrique (basée sur le Test de Repérage des Difficultés en Mathématiques) réalisée au Sénégal en novembre 2021 auprès de 2973 élèves de l’école primaire afin d’évaluer les performances en calcul mental. L'étude a été complétée par une enquête sociologique sur les représentations associées aux mathématiques à laquelle ont participé 470 enfants. L'analyse des résultats des deux enquêtes, parfois contradictoires, a requis une approche épistémologique complexe mais elle permis d'identifier des pistes concrètes permettant d'imaginer des stratégies didactiques plus contextualisées et plus efficaces pour l’apprentissage des mathématiques (et du calcul mental)
