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Importance of the microphytobenthos in the foodweb of tropical mudflats
No full textInternational audienceMudflats are peculiar dynamic ecosystems, at the interface of terrestrial and aquatic ecosystems, known for their large carbon storage ability. Mudflats also provide food source and constitute important habitats for photosynthetic organisms and consumer communities. Tropical mudflats are highly unstable and only temporarily accessible to either aquatic or aerial consumers because of tides, which raises the question of the trophic functioning of these habitats. Their importance in terms of trophic resources for species that temporarily feed there as well as the carbon origin of mudflat foodweb deserve to be explored. This was assessed, over a year in a tropical mudflat (French Guiana) at two sites (Sinnamary and Awala-Yalimapo), from primary producers to predators, using stable isotope ratios (δ13C and δ15N) as a proxy of their diet. The results showed that trophic interactions were similar in each site and only a few influences of the seasons were detected for the meiofauna (Halomonhystera sp.), and fish (Gobionellus oceanicus only in Sinnamary). The microphytobenthos constituted the dominant primary source incorporated by the meiofauna, which in turn was an important one for the fish. The three shorebird species depended mainly on the microphytobenthos, green algae and Tanaidacea and secondarily on the meiofauna. The two resident fishes relied on the same sources as the birds but incorporating higher proportions of the meiofauna taxa (Copepoda, Nematoda, and Ostracoda). The analyses of species niche overlaps between the three shorebirds and the two resident fish demonstrated that they might compete for resources. The results are discussed in relation to the central place of the MPB as a direct or indirect source of carbon for the vast majority of organisms present on these tropical mudflats, whether transient or resident species
Single‐Step Isolation of Phyllacanthone From Cnidoscolus quercifolius Using Centrifugal Partition Chromatography
No full textInternational audienceABSTRACT Favelines, benzocycloheptene diterpenes exclusively found in Cnidoscolus quercifolius , have shown promising anticancer properties, particularly phyllacanthone. Nevertheless, the isolation of these compounds remains challenging due to their similar polarity. The use of centrifugal partition chromatography (CPC) has enabled the quick and efficient purification of phyllacanthone from C. quercifolius crude extract with a yield of 4.5% (w/w) and a purity of 83%. Favelines‐enriched fractions were also obtained and purified by preparative HPLC, resulting in the isolation of faveline, isofavelol, and deoxofaveline. In addition, phyllacanthone B, a previously unreported derivative, was identified and characterized. Pharmacological evaluations revealed the significant anti‐melanoma activity of purified metabolites, with distinct structure–activity relationships. These results shed light on the mechanism of action of favelines, suggesting their potential as hits for the development of novel anticancer agents
Better together than alone: sociality mitigates the negative impact of early family disruption on adult problem-solving performance in zebra finches
No full textInternational audienceAdolescent cognitive development, characterized by social learning and innovation, is sensitive to social disruptions. We investigated how family disruption during emancipation affects adult problem-solving performance in social contexts. We manipulated the social environment of 22 zebra finch ( Taeniopygia guttata ) broods during emancipation by replacing the biological father with an unfamiliar male or by leaving the family intact. In adulthood, offspring underwent a social task, solving a novel problem with their siblings. Then, they had to complete the same task on their own to evaluate the persistence of the treatment effects after the social task. Experimental individuals were less successful than controls in the social task. Although average brood performance was similar, experimental broods showed greater heterogeneity than controls. In the isolated trial, the differences between experimental and control individuals disappeared. Our findings suggest that family disruption during emancipation affects individual problem-solving skills in social settings. However, the success of a few siblings in experimental broods, who likely shared their discoveries, compensated for this impairment and improved overall brood performance. These individuals likely provided social information during the social trial, and this probably benefitted their siblings during the isolated trial. We emphasize the importance of studying animal cognition in social settings and the role of social learning in mitigating cognitive impairments
Polytopic approach for stability and control design of Saint-Venant equations
No full textInternational audienceThe polytopic approach offers a powerful framework for addressing the stability and controldesign of systems with parameter-dependent dynamics, especially when these parameters varywithin a known range. Applying this to the Saint-Venant equations, which are nonlinear partialdifferential equations (PDEs) modeling shallow water flows (such as in rivers, channels, orurban drainage), is a way to handle uncertainties and nonlinearities.Indeed, the Saint-Venant equations describe the conservation of mass and momentum in open-channel flow. They are typically nonlinear and can be quite challenging for stability and controldesign due to their inherent nonlinearities and the presence of varying physical parameters suchas water height, flow velocity, channel slope, and friction coefficients. These parameters areoften subject to uncertainties and spatial-temporal variations, making classical linear controlmethods inadequate or overly conservative.The polytopic approach helps by approximating these nonlinear PDEs with a set of linearparameter-varying (LPV) models, whose parameters stay within a convex polytope. The keyadvantage of the polytopic method is that by guaranteeing stability and performance at thesevertex systems through Linear Matrix Inequalities (LMIs), one can ensure robust stability andcontrol for all parameter variations within the polytope due to convexity properties.Furthermore, by seeking a common Lyapunov function valid for all vertices, the methodensures global stability over the entire operating range, which is essential for the practicalcontrol of water systems exposed to dynamic inflows, environmental disturbances, andstructural uncertainties.The polytopic approach thus provides a systematic and computationally tractable way to designcontrollers capable of regulating water levels, flow rates, or other objectives in open-channelflows while explicitly considering model uncertainties and nonlinearities through the convexhull of parameter variations. This makes it an appealing strategy for modern water managementchallenges, where safety, resilience, and efficiency are critical under uncertain and time-varying conditions
Toward a unified approach to modelling adaptation among demographers and evolutionary ecologists
No full textInternational audience1. Demographic and evolutionary modelling approaches are critical to understanding and projecting species responses to global environmental changes. Population matrix models have been a favoured tool in demography, but until recently, they failed to account for short-term evolutionary changes. Evolutionary-explicit demographic models remain computationally intensive, difficult to use and have yet to be widely adopted for empirical studies. Researchers focusing on short-term evolution often favour individual-based simulations, which are more flexible but less transferable and computationally efficient. Limited communication between fields has led to differing perspectives on key issues, such as how life-history traits affect adaptation to environmental change. We develop a new EvoDemo hyperstate matrix population model (EvoDemo-Hyper MPM) that incorporates the genetic inheritance of quantitative traits, enabling fast computation of evolutionary and demographic dynamics. We evaluate EvoDemo-Hyper MPM against individual-based simulations and provide analytical approximations for adaptation rates across six distinct scales in response to selection. We show that different methods yield equivalent results for the same biological scenario, although semantic differences between fields may obscure these similarities. Our results demonstrate thatEvoDemo-Hyper MPM provides accurate, computationally efficient solutions, closely matching outcomes from individual-based simulations and analytical approximations under similar biological conditions. Adaptation rates per generation remain constant across species when selection acts on fertility but vary with other vital rates. Adaptation per time decreases with generation time unless selection targets adult survival, where intermediate life histories adapt fastest. Rates per generation, defined as the relative change in individual fitness, remain constant across species and vital rates.4. We discuss that no general prediction emerges about which species or life-history traits yield higher adaptation rates, as outcomes depend on life cycles, vital rates | 1645 VAN de WALLE et al. </div
Le chevalier a la robe vermeille - Édité d'après le ms. BnF fr. 837
No full textLe chevalier a la robe vermeille - Édité d'après le ms. BnF fr. 83
Une seule santé en droit : avancées et perspectives, in (SFE2) RO27 Regards: R027, Société Française d'Ecologie et d'Evolution SFE2, Regards
No full textSociété Française d'Ecologie et d'Evolution, RegardsLes liens entre environnement et santé sont reconnus au plan international et national depuis de nombreuses années dans différents domaines scientifiques. Le concept « One health » (en anglais) ou « Une seule santé » (en français) vise quant à lui à développer une approche plus globale et systémique prenant en considération l’interdépendance entre les humains, les animaux, les végétaux et des écosystèmes. Or, depuis la définition du principe « Une seule santé » par le groupe consultatif indépendant auprès de l’Alliance Quadripartite le One Health High-Level Expert Panel (OHHLEP), il est devenu particulièrement important d’avoir une définition juridique du principe. La Société Française pour le Droit de l’Environnement (SFDE) a ainsi lancé un travail pour élaborer un projet/proposition de loi « Une seule santé » adaptée à la France, sous l’égide de l’Alliance Santé Biodiversité (ASB). Les conclusions de ce travail collectif et le projet de loi résultant sont présentés dans ce Regard
Bout time for krill: contrasting Adélie penguin foraging behaviour during years of high and low krill availability
No full textInternational audienceUnderstanding how marine predators structure and adjust their foraging in response to prey-field characteristics is a longstanding objective in marine ecology. This is particularly challenging in Southern Ocean ecosystems, where logistical and financial constraints hinder assessment of predator foraging and prey-field information at relevant spatial and temporal scales. Here, we examine how Adélie penguins (Pygoscelis adeliae) -a key Southern Ocean indicator species -perform and organise their foraging behaviour during two contrasting years of krill (Euphausia superba) abundance. Using multi-year krill-acoustic data from King George Island in the West Antarctic Peninsula (WAP), we assess broad seasonal conditions in krill availability. We also analyse a suite of penguin bio-logging data (spatial location, dive and accelerometry-derived activities) during the same period to identify broad behavioural differences in their bout-diving activity, a classical measure of the temporal organisation of foraging in diving predators. During years of high krill abundance and availability, penguins perform shorter dive bouts (consisting of shallower and shorter duration dives), which are more concentrated in time and space. Despite these differences in bout structure, prey capture attempts occur at the same rate within bouts. These findings challenge traditional interpretations assuming that an increased bout duration (and related proxies of prey capture effort) signals increased krill patch abundance and profitability. Although additional data are required to understand the full scope of penguin bout diving and krill prey-field associations, our work improves understanding of penguin behavioural variation and provides insights into how foraging behaviours could potentially be used to interpret krill availability at predator and management-relevant scales
High resolution data reveal fundamental steps and turning points in animal movements
No full textInternational audienceAnimal movement paths display substantial complexity and variability, leading researchers to seek underlying rules that govern these patterns and mathematical models that best describe them. Using high-resolution (≥ 10 Hz) movement from 43 vertebrate species across diverse taxa, mass, and lifestyles, we show that movement paths are universally composed of straight-line steps interspersed with sharp turns, echoing a pattern documented for lower taxa such as bacteria. We report how these vertebrate ‘fundamental step lengths’ and ‘fundamental turn angles’, which are intrinsically different from the straight-line paths detailed in studies using low resolution position data, vary with species’ mass, lifestyle, behaviour, and environmental context. To explain these, we posit that animals inherently move in a straight line until sensory information signals a perceived better heading, which instigates a turn. The constellation of fundamental step lengths and turn angles over varying time intervals affects how well different models of animal movement (such as random walk or Lévy flight) fit lower resolution data. By examining turns as decision points, we can seek drivers of animal movement patterns and thereby work to predict future paths under varying conditions
Mass mortality events in the sub-Antarctic Indian Ocean caused by long-distance circumpolar spread of highly pathogenic avian influenza H5N1 clade 2.3.4.4b
No full textInternational audienceSince 2020, the outbreak of highly pathogenic avian influenza (HPAI) virus clade 2.3.4.4b has turned into the largest documented panzootic to date, reaching the sub-Antarctic region and Antarctica via the tip of South America in 2023. Here, we describe its recent arrival into the Indian Ocean sub-Antarctic archipelagos of Crozet and Kerguelen, where we first detected the virus in October 2024 in dead southern elephant seals, king penguins, gentoo penguins, brown skuas and kelp gulls. While the panzootic is ongoing, it has already caused unprecedented and alarming mortalities of southern elephant seals. We collected brain swabs from various seal and bird carcasses, subsequently isolated the virus and obtained 25 novel HPAI H5N1 clade 2.3.4.4b sequences. Our phylogenetic and phylogeographic analyses show that there have been independent introductions of the virus to Crozet and Kerguelen, from the distant South Georgia Islands in the Southern Atlantic, and not from the more nearby coasts of South Africa. Our results point to a year-long gap in genomic surveillance in the south polar region, obscuring how HPAI H5N1 clade 2.3.4.4b is spreading in the sub-Antarctic and illustrating the difficulties in tracking pathogen dispersal in the region. Locally, our phylogenetic analyses show that the virus is transmitted between different species. Moreover, our serological analyses show that some southern elephant seal pups had mounted an anti-H5 antibody response. With the spread to Crozet and Kerguelen, HPAI H5N1 2.3.4.4b is moving ever closer to Australia and New Zealand, which currently remain free from infections with this strain, and represents a major threat to the sub-Antarctic wildlife. Our results provide key elements to enable stakeholders to anticipate the arrival and spread of the virus in remote areas of critical wildlife conservation concerns