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How the diet influences lepidopteran reproduction: Morpho-functional, behavioral, and endocrine aspects
No full textInternational audienceIn insects, diet influences the accomplishment of physiological functions, such as reproduction. The study of interactions between diet and reproduction, which involve morpho-functional, behavioral, and endocrine aspects, is necessary for identifying the features of the adaptive strategies of insects in their natural environment. This review delves into the intricate relationship between nutrition and reproductive processes in female and male Lepidoptera. Indeed, nutrient-rich diets are crucial for reproductive success by accelerating ovarian and testicular development, egg maturation, sperm synthesis and migration, and accessory sex gland maturation. Moreover, such diets boost the biosynthesis and release of sex pheromones and promote pheromonal detection by the olfactory system, thus eliciting sexual displays. These physiological and behavioral changes increase fertilization rate and offspring production, highlighting the importance of balanced diets in sustaining insect populations. Then, the review explores the molecular mechanisms by which the evolutionary conserved insulin signaling pathway acts as a transducer of nutritional inputs in linking with the regulatory actions of a major reproductive hormone, namely juvenile hormone. Finally, this review provides a greater comprehensive and integrated understanding of adult diet influence on lepidopteran reproduction, and also opens up new research avenues in the fields of agricultural pest control and ecotoxicology
Deciphering the biosynthetic landscape of biofilms in glacier-fed streams
No full textInternational audienceGlacier-fed streams are permanently cold, ultra-oligotrophic, and physically unstable environments, yet microbial life thrives in benthic biofilm comm
Evenness peaks in fire-resilient vegetation preceded ecosystem shifts in East Africa
No full textInternational audienceFire is often assumed to be a key driver in shaping tropical vegetation structure and composition in grass-dominated ecosystems, while forests experience infrequent but impactful fires that influence ecosystem resilience. Although short-term interactions between fire and vegetation are well-documented, long-term dynamics remain underexplored. This study examines fire regimes, vegetation dynamics, and its biodiversity over the past 17 000 years in southwest Tanzania, using sedimentary charcoal and pollen. Major ecological transformations of vegetation and fire regimes were recorded, with vegetation changes consistently preceded shifts in fire regimes. Increased grass pollen correlated with more frequent or larger fires, while high tree cover in Miombo woodland reduced fire activity. Interestingly, pollen evenness was a precursor to major ecological transformations as peaks preceded changes in ecosystem states. Changes in precipitation and moisture seems the major top–down drivers of these changes in vegetation and fire. Fire regimes were indirectly controlled by water availability, and vegetation exhibited resilience to fire at centennial timescales before reaching ecosystem shifts at 12 400 and 1700 cal BP. Our results emphasize the critical role of tree and grass cover in shaping fire regimes and highlight the interplay between climate, vegetation structure, and fire in East African ecosystems
Aggregation Behaviour as an Adaptive Reproductive Strategy in a Marine Ecosystem Engineer
No full textInternational audienceAggregation behaviour is a key process shared by numerous organisms, providing benefits such as predator protection, resistance to abiotic stressors and enhancing reproductive success. In coastal waters, mussel aggregations shape ecosystems and increase biodiversity; however, many aspects of this ecologically key behaviour remain unexplored. Here, we investigated the potential link between aggregation rate and reproductive maturity stages in the blue mussel Mytilus edulis over a seasonal cycle. We showed that the seasonality of M. edulis aggregation rate was a significant sinusoidal function of the mean reproductive maturity stage. Specifically, aggregation increased during gamete maturation until the onset of spawning and subsequently declined, following a cyclical pattern, supporting a reproductive function of this aggregation behaviour in mussels. Given the ubiquity of plastics as marine contaminants and their known harmful effects on organisms, we subsequently assessed how the temporal patterns observed in aggregation behaviour may be impacted by an exposure to leachates from plastic pellets. Thus, an exposure to plastic leachates led to a loss of the cyclical pattern observed in control seawater, potentially compromising mussel reproduction and the stability of mussel bed habitat. Our study showed the relationship between aggregation behaviour, reproduction and contaminants in mussels. Understanding these complex interactions is crucial, given the pivotal role mussels and their aggregations play in shaping marine ecosystems, offering new insights into the resilience of this habitat facing contemporary challenges
Quand Fa (ne) parle (pas) d’esclavage : une mémoire en filigrane
No full textThis paper offers a specular exploration of the presence—or absence—of traces of the transatlantic slave trade and slavery within the Fa divination narratives from the Bight of Benin. Rooted in a ritual practice primarily oriented towards immediate action and the resolution of individual concerns, these narratives prioritize contemporary and personal issues, relegating the memory of slavery to the margins of ritual consultation. The theme of slavery, as either a collective or individual threat, only appears marginally and does not constitute a dominant motif within the corpus.The study is based on the analysis of 232 divination narratives, supplemented by in-depth interviews with several major diviners from Cotonou. It reveals that references to slavery, when they do occur, take on indirect forms—lexical, metaphorical, or anecdotal—without resulting in an explicit transmission of historical memory of the trade. However, five distinctive narratives stand out for their ability to evoke, through symbolic motifs—animal figures, inversions of order, valorizations of creative processes—implicit forms of resistance, survival, and resilience.By proposing a contemporary reading of the corpus, attentive both to silences and to subtle emergences of memory, this study interrogates the dynamics of the transmission of a buried, displaced, or metamorphosed memory. In doing so, it sheds light, through a mirror effect, on the resonances between African narratives and the memorial echoes present in Afro-diasporic societies.Cette communication propose une exploration spéculaire de la présence — ou de l'absence — de traces de la traite transatlantique et de l'esclavage dans les récits de divination Fa issus du Golfe du Bénin. Ancrés dans une pratique rituelle principalement orientée vers l’action immédiate et la résolution des préoccupations individuelles, ces récits privilégient des enjeux contemporains et personnels, reléguant ainsi la mémoire de l’esclavage à la périphérie de la consultation rituelle. La thématique de l'esclavage, en tant que menace collective ou individuelle, n’émerge que de manière marginale, ne constituant pas un motif dominant au sein du corpus.L'étude s'appuie sur l’analyse de 232 récits divinatoires, ainsi que sur des entretiens approfondis avec plusieurs devins majeurs de Cotonou. Elle met en évidence que les références à l'esclavage, lorsqu'elles existent, se déploient sous des formes détournées — lexicales, métaphoriques, ou anecdotiques — sans donner lieu à une transmission explicite d'une mémoire historique de la traite. Toutefois, cinq récits singuliers se démarquent par leur capacité à faire affleurer, à travers des motifs symboliques — figures animales, renversements d’ordre, valorisation des processus créatifs —, des formes implicites de résistance, de survie et de résilience.En proposant une lecture contemporaine du corpus, attentive aux silences autant qu'aux émergences subtiles de la mémoire, cette étude interroge les dynamiques de transmission d'une mémoire enfouie, déplacée ou métamorphosée. Elle éclaire ainsi, par effet de miroir, les résonances entre les récits africains et les échos mémoriels présents dans les sociétés afro-diasporiques
Inorganic carbon dynamics and their relation to autotrophic community regime shift over three decades in a large, alkaline river
No full textInternational audienceHow much of the excess CO 2 in running waters comes from in‐stream respiration of organic carbon? To answer this, we developed a 30‐yr metabolism‐carbonate system database at an hourly resolution for the Loire River, France, a large, alkaline river. We asked the following questions: what are the intra‐annual patterns of in‐stream (“internal”) CO 2 production, what processes drive these patterns, and how do these patterns depend on autotrophic community composition? We estimated internal CO 2 production as the ratio of net ecosystem production to CO 2 water‐to‐air flux (FCO 2 ). We also estimated the daily ecosystem quotient (EQ, O 2 released: dissolved inorganic carbon [DIC] consumed) and the prevalence of non‐CO 2 autotrophic DIC uptake pathways under CO 2 depletion. Median internal CO 2 production was 49% of FCO 2 in the Loire from 1990 to 2022. The river predictably shifted from a heterotrophic, CO 2 source to an autotrophic, CO 2 sink as a function of discharge, leading to four trophic‐flux (“trophlux”) states: autotrophic‐sink, autotrophic‐source, heterotrophic‐sink, and heterotrophic‐source. During autotrophic states (41% of the time), CO 2 depletion (FCO 2 ≤ 0, median pCO 2 = 135 μ atm) led to the use of and of CO 2 released by CaCO 3 precipitation as alternative DIC sources to autotrophs to support their high rates of primary production (occurring on average for 33% of the growing season). Finally, during a period of phytoplankton dominance, the median EQ was 1.3, which was reduced to 1.0 under macrophyte dominance. This work describes a dynamic coupling among autotrophic communities, calcium carbonate equilibria, and discharge‐controlled FCO 2 that together imply lower‐than‐predicted FCO 2 magnitude and greater‐than‐predicted internal CO 2 production for the Loire River
Temperature-dependent versatility shapes invasiveness in the tropical freshwater gastropod Melanoides tuberculata: Versatility shapes invasiveness in M. tuberculata
No full textInternational audienceInvasive species cause major losses in biodiversity worldwide and alter ecosystem functioning. Once established, invaders are often impossible to remove from ecosystems, especially in eco-insular systems such as the African Great Lakes. How intrinsic biological properties of invasive taxa interact with human-induced ecosystem modifications is a crucial factor determining invasiveness and our ability to anticipate, prevent and manage bioinvasions. Here we investigate the influence of temperature on key life-history traits, including fecundity, growth, offspring size, survival and parental immune investments, of invasive Asian Melanoides tuberculata (Müller, 1774) from Lake Malawi/ Nyassa (morph LMI). We subjected populations of this parthenogenetic (clonal) lineage to uniform temperature treatments of 20 °C, 26 °C and 32 °C and monitored adult and juvenile life-history traits. Constitutive (preventative) and infection-induced immune investments of adults were estimated via antibacterial responses to a natural pathogen. Fecundity was low during our experiment and did not differ amongst temperature treatments, but a burst of offspring release occurred in the first two weeks of the experiment. Juvenile size and growth increased with temperature, which resulted in decreasing generation times. Juvenile mortality was, however, elevated at 32 °C. Temperature differences prompted a shift in immune investments. Under cold temperatures, adults invested in costly constitutive immunity, but they did not in warm environments, where strong investments in infection-induced immune responses occurred. This strategy may enable adults in warm environments to redirect energy from immunity to growth and reproduction, therewith, enhancing competitiveness at the cost of reduced offspring survival. We observed contrasting responses in various studied traits, suggesting that Melanoides tuberculata adopts compensatory mechanisms to cope with environmental changes. This versatility favours invasiveness and contributes to the competitive pressure which invasive Melanoides exerts on native taxa amid global warming and ecosystem change. Understanding the intricate interactions between bioinvasions and environmental change is essential for effective conservation of native species, the stability of their ecosystems and for policy development. Species-specific versatility of invasive species and associated competitive advantages remain understudied, but are critical to predict invasion dynamics in the context of multidimensional anthropogenic stressors, for informed risk assessment and decision-making.</div
Cultures afro-descendantes des Amériques: entre survivance et effacement
No full textCultures afro-descendantes des Amériques: entre survivance et effacementInternational audienceThis article explores the stark contrast between Afro-descendant cultures across the Americas. While countries such as Brazil, Cuba, and Haiti display rich and ongoing African cultural survivals, the African-American culture in the United States seems, by comparison, to exhibit an absence or erasure of African roots. The author argues that this is not a result of assimilation, but of a deliberate symbolic destruction engineered by the American slave system.The U.S. model of slavery aimed to break familial ties, eradicate languages, and erase religious and cultural practices, effectively attempting to produce a new kind of being: culturally void, socially isolated, and politically neutralized. In contrast, Latin American slavery, though also violent, allowed for more cultural blending and African retention.American creations like jazz, gospel, and blues are interpreted here not as signs of assimilation but as artistic responses to cultural suffocation—forms of survival through reinvention under constraint. These expressions were often misread by white society as integration, masking their radical resistance nature.The article critiques generalized theories such as creolization, particularly as developed by scholars like Mintz, Price, and Glissant. While valuable in some contexts, the concept may act as a conceptual smokescreen, obscuring the historical singularity and trauma of the African-American experience. A theoretical framework that overemphasizes blending risks depoliticizing the unique cultural genocide faced by African Americans.In conclusion, the piece calls for a differentiated analysis of Afro-diasporic histories, cautioning against overly universal frameworks that fail to account for structural and ideological differences between colonial regimes.Cet article analyse les contrastes entre les cultures afro-descendantes des Amériques, en mettant en lumière la survivance culturelle africaine manifeste dans des pays comme le Brésil, Cuba ou Haïti, et l’effacement symbolique observé dans la culture afro-américaine des États-Unis. Il avance que cette différence ne relève pas d’un simple processus d’assimilation, mais d’un projet idéologique de destruction culturelle propre au système esclavagiste américain, fondé sur la déshumanisation, la rupture des filiations, et l’interdiction des langues et religions africaines.Les expressions culturelles afro-américaines telles que le jazz, le blues ou le gospel sont ainsi interprétées comme des formes de résistance créative, issues d’un contexte de vide culturel imposé, souvent mal comprises ou récupérées comme signes d’intégration. L’article critique également les généralisations théoriques autour de concepts comme la créolisation, qui tendent à neutraliser la spécificité du traumatisme afro-américain en l’insérant dans une logique trop uniforme de métissage ou de résilience culturelle.La conclusion insiste sur la nécessité de reconnaître les singularités historiques des différents systèmes esclavagistes pour ne pas dépolitiser les mémoires afro-descendantes sous couvert d’universalité théorique
Escherichia coli in the Niger River: Links to environmental variables and anthropogenic activities in Niamey city, Niger
No full textInternational audienceStudy region: Middle Niger River, upstream to downstream of Niamey city, Sahel, West Africa.Study focus: Understanding surface water pollution dynamics and identifying its main drivers isparticularly important in regions where surface waters are largely used without proper treatment.This study is focused on the Niger River water and assesses E. coli numbers, and physicochemicalparameters upstream and downstream of Niamey. Data collected over three years, supplementedby occasional campaigns, aimed to determine the spatial and temporal variability of waterquality.New hydrological insights for the region: SPM and E. coli showed high values during the rainyseason, peaking before the Red flood. E. coli increased from the first rainfall events in Niameywith a peak occurring before SPM peak. Distinct sources play an important role on their seasonaldynamics; E. coli mainly originates from urban areas along the Niger River, while SPM comesfrom right-hand tributaries upstream of Niamey. Downstream of Niamey, E. coli were significantlyhigher than upstream, highlighting the city’s substantial contribution to fecal contaminationthrough wastewater discharges, particularly on the left bank. No significant differences betweenupstream and downstream were observed in the other physicochemical parameters analyzed.Considering spatial distribution in E. coli sources and environmental parameters such as rainfalland SPM is of major and global importance for understanding and addressing fecal contaminationin urban environments
SARRA, histoire d'un modèle de simulation des cultures pour les zones intertropicales
No full textInternational audienceThe SARRA (Regional Analysis System for Agroclimatic Risks) model family has been under development by the French Agricultural Research Centre for International Development (CIRAD) since the 1970s. Used in intertropical regions, the early versions of the model were designed to assess the impact of water stress—that is, the lack of accessible water for crops—on production and seedling losses. Their objectives were to improve riskestimation, optimize sowing management, and serve as a regional-scale early warning system for food security. Since the 2000s, the model has been increasingly used to analyze the impacts of climate change on agroclimatic risks. Several developments have enabled the integration of, on the one hand, the genetic characteristics of crops, and on the other hand, a better consideration of spatio-temporal dynamics, particularly through the use of remote sensing. Additionally, SARRA has gradually evolved from a descriptive model into a scenario-based anticipation tool, requiring structural transformations and the adoption of modern programming and versioning techniques to ensure traceability and reproducibility of simulations. Recognized for their simplicity, parsimony, and robustness, these models have proven effective for monitoring agricultural seasons, managing foodsecurity, and supporting decision-making in the face of climate risks. This article provides a retrospective analysis of their development, highlighting major innovations and their potential to guide resilient agricultural practices in response to current climate challenges.La famille de modèles SARRA (Système d'Analyse Régional des Risques Agroclimatiques) est développée par le CIRAD depuis les années 1970. Utilisées dans les régions intertropicales, les premières versions du modèle permettaient d'évaluer l'impact des stress hydriques, c'est-à-dire le manque d'eau accessible par la culture, sur sa production ainsi que les pertes de semis. Elles avaient pour objectif d'améliorer l'estimation des risques, la gestion des semis et de servir de système d'alerte à l'échelle régionale pour la sécurité alimentaire. À partir des années 2000, le modèle a été sollicité pour analyser les effets du changement climatique sur les risques agroclimatiques. Plusieurs évolutions ont permis d'intégrer, d'une part, les caractéristiques génétiques des plantes et, d'autre part, une meilleure prise en compte des dynamiques spatio-temporelles, notamment par le biais de la télédétection. Par ailleurs, SARRA a progressivement évolué d'un modèle descriptif vers un outil d'anticipation et de simulation de scénarios, nécessitant des transformations structurelles et l'adoption de techniques modernes de programmation et de versioning afin d'assurer la traçabilité et la reproductibilité des simulations.Reconnus pour leur simplicité, parcimonie et robustesse, ces modèles se sont avérés efficaces pour le suivi des campagnes agricoles, la gestion de la sécurité alimentaire et la prise de décision face aux risques climatiques. Cet article propose une rétrospective de leur développement et met en lumière les innovations majeures ainsi que leur potentiel pour guider des pratiques agricoles résilientes face aux défis climatiques actuels