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Impacts of Nearby Algae on Recruitment Success and Early Microbiome Development of the Coral Acropora cytherea
No full textInternational audienceThe persistence of coral reefs is dependent on the arrival and settlement of coral larvae followed by their post‐settlement growth and survival. Despite evidence showing that benthic algae have variable effects on corals, it is still unclear how benthic communities of the coral nursery habitat impact the early development of the coral microbiome and if these impacts relate to the survival and growth of newly settled corals. Here, we tested whether the survival and growth of Acropora cytherea recruits are impacted by surrounding algae, and whether specific algae influence their associated bacterial and Symbiodiniaceae communities. A 6‐month survey of coral larvae experimentally settled near different algae showed that crustose coralline algae enhanced recruit survival. However, despite variation in their microbiome, the presence of different algae did not impact the coral microbial community composition. The recruit microbiome was colonised by bacteria shared among all benthic substrates rather than bacteria unique to specific algae. Furthermore, the microbiome of coral larvae was different from that of the recruits. We conclude that the microbiome of corals in their early life stages is structured by host ontogeny rather than by their surrounding benthos, but that the surrounding benthos contributes to the transfer of opportunistic bacteria
New species of Endaeus Schoenherr, 1826 (Curculionidae: Curculioninae: Ochyromerini) associated with Annonaceae and Clusiaceae
No full textInternational audienceRepresentatives of the weevil tribe Ochyromerini (Coleoptera: Curculionidae: Curculioninae) have been increasingly reported as specialized pollinators of Annonaceae Juss., with some species in the genus Endaeus Schoenherr, 1826 engaging in brood-site pollination with their host. Recent investigations into the poorly documented life history of these pollinators have led to the discovery of new species in the genus Endaeus and provided details of their life histories. The following species are herein described: E. canangae Haran sp. nov. from Southeast Asia, associated with Cananga odorata (Lam.) Hook.f. and Thomson (Annonaceae); E. lenticulatus Haran sp. nov. from Central Africa, associated with Uvariodendron molundense (Diels) R.E.Fr. (Annonaceae); E. xylopiae Haran and Zelvelder sp. nov., E. jaculifer Haran and Zelvelder sp. nov. and E. convexiculus Haran and Zelvelder sp. nov. from Central Africa, associated with Xylopia aethiopica (Dunal) A.Rich. (Annonaceae) and E. staminicola Haran sp. nov. also from Central Africa, associated with Allanblackia floribunda Oliv. (Clusiaceae Lindl.). Pictures of habitus and terminalia of adults, molecular and morphological diagnostic tools along with life history data are provided for each species. These new associations are discussed in light of the general patterns of specialized brood-site pollination mutualism between plants and weevils
How Random Connectivity Shapes the Fluctuating Dynamics of Finite-Size Neural Populations
No full textInternational audienceMesoscopic models of finite-size neuronal populations are crucial to understand the dynamics of neural networks in the brain, especially their fluctuations and response to stimuli. However, current theories to derive such models are based on the assumption of homogeneous all-to-all (full) connectivity, neglecting the variance in the connectivity of biologically realistic networks with connection probabilities p<1 (nonfull connectivity). To gain insight into the different fluctuation mechanisms underlying the neural variability of populations of spiking neurons, we derive and analyze a stochastic mean-field model for finite-size networks of Poisson neurons with random connectivity (including nonfull connectivity), external noise, and disordered mean inputs. We treat the quenched disorder of the connectivity by an annealed approximation enabling a doubly stochastic description of synaptic inputs for finite network size. A further reduction leads to a low-dimensional closed system of coupled Langevin equations for the mean and variance of the neuronal membrane potentials as well as a variable capturing finite-size fluctuations arising specifically in the case of connectivity disorder. Comparing to microscopic simulations, we find that the mesoscopic model describes the fluctuations and nonlinearities well and outperforms previous mesoscopic models that neglected the variance in the connectivity. The joint effect of connectivity disorder and finite network size can be analytically understood by a softening of the effective nonlinearity and the multiplicative character of spiking noise. The mesoscopic theory shows that quenched disorder can stabilize the asynchronous state, and it correctly predicts large quantitative and nontrivial qualitative effects of connection probability on the variance of the population firing rate and its dependence on stimulus strength. Our theory thus elucidates how disordered connectivity shapes nonlinear dynamics and fluctuations of neural populations at the mesoscopic scale and showcases a useful mean-field method to treat random connectivity in finite-size, spiking neural networks
How generics obscure the logic of conditionals
No full textInternational audienceThis paper discusses counter‐examples to modus ponens and modus tollens involving modals and quantificational adverbs, and presents new counter‐examples with generic conditionals. We argue that the counter‐examples are spurious, and are explained by the domain‐restricting effects of if ‐clauses. Generic conditionals are especially problematic because the generic operator is silent and detectable only through its interpretive effects. A second, experimental case study involving nested conditionals illustrates the ease with which generic conditionals can mislead theorists about the logic of conditionals. To avoid pitfalls, theorists choosing examples and designing experimental materials must pay close attention to the special linguistic properties of generics
Microfluidics Resolves Non-Classical Lysozyme Nucleation Driven by Attractive Protein Interactions
No full textInternational audienceProtein crystalline nucleation pathways still remain a hot research topic after decades, due to the experimental challenges involved in its study and its vast implications in several applied and research fields. Here, we report a comprehensive investigation of lysozyme crystal nucleation, employing a high-throughput droplet-based microfluidic chip, developed ad-hoc for performing crystal nucleation kinetic measurements, and Dynamic Light Scattering (DLS) for local solution structure analysis. A temperature-controlled system with 500 independent nL-scale droplet microreactors enabled statistical analysis of nucleation events, and two distinct nucleation rates were identified, one attributed to prevalent heterogeneous nucleation (likely on impurities and/or denatured protein molecules), and the other to nucleation in the bulk of the solution. CNT-derived kinetic parameters for bulk nucleation aligned with previously reported values, yet deviated significantly from classical homogeneous predictions: the estimated density of active nucleation sites was found to be several orders of magnitude lower than the protein monomer concentration, strongly contradicting a homogeneous mechanism. Furthermore, when approaching the binodal, nucleation kinetics exhibited a marked deviation from the CNT trend, indicating a rupture in the nucleation behavior. DLS analysis further indicated that in supersaturated conditions, proteins do not remain monomeric but form dynamic locally densified regions. Results show that lysozyme nucleation proceeds via transient densifications driven by attractive intermolecular interactions, challenging the classical view of a homogeneous, monomer-dominated solution and underscoring the importance of mesoscopic solution structure.</div
Compte-rendu François Dolbeau , Bibliothèques médiévales. Inventaires et lecteurs. Recueil d’articles en l’honneur de son 75 e anniversaire , éd. Benedetta Valtorta , Florence, SISMEL–Edizioni del Galluzzo, 2023
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Intermediate-complexity parameterisation of blowing snow in the ICOLMDZ AGCM: development and first applications in Antarctica
No full textInternational audienceRecent regional model findings suggest that the aeolian erosion of surface snow is a significant contribution to the overall Antarctic surface mass balance (SMB) through ice crystals sublimation and export outside of the ice sheet. Such findings raise the question of the relevance of accounting for such a process also in global climate models. This study presents the development of an intermediate-complexity parameterisation of blowing snow for the ICOLMDZ atmospheric general circulation model, the atmospheric component of the IPSL Coupled Model. The parameterisation is designed to be a trade-off between physical complexity and applicability in a general circulation model, with constraints on numerical cost and stability. The parameterisation is evaluated with in situ observations using limited-area simulations over Adélie Land. The model exhibits satisfactory results in terms of summer wind speed, temperature and intensity of blowing snow fluxes. In winter, blowing snow intensity and occurrences are overestimated close to the coast, concurring with a positive wind speed bias. In terms of blowing snow occurrences throughout the year, ICOLMDZ exhibits comparable performance with the regional atmospheric model MAR. Boundary-layer moistening and cooling as well as changes in surface radiative fluxes due to blowing snow crystals are also quantified in the simulations. Global simulations at standard global climate model resolution are carried out to investigate how the Antarctic SMB is modified with the activation of the blowing snow parameterisation. Results show an overall decrease of the net snow accumulation in the escarpment region due to surface snow erosion and an increase along the coast due to blowing snow deposition and increase in precipitation
“The EU borders and their procedures. Considerations relative to the fictions of non-entrée”, communication durant la conférence annuelle du European Immigration Law Network, Paris, 29 mai 2026.
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“Legal Modelling of EU Borders: a Three Dimensions Approach”, communication durant The Fez Border Studies Conference II - Interdisciplinary Dialogues on Borders, Walls, and Security, Université Sidi Mohammed Ben Abdellah (Laboratory of Legal and Political Studies), en collaboration avec l'Université de Québec à Montréal (Chaire Raoul-Dandurand), l'INALCO (France), la Arizona State University (School of Transborder Studies, USA), et la South Asia University (India), Fès, 18-21 mai 2026.
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