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Area-dependent environmental effects shape physiological characteristics in three small pelagic fish populations
No full textInternational audienceIdentifying and monitoring the processes underlying changes in individual life-history traits and population size are essential to better predict natural populations' responses to environmental changes and sustainably manage natural resources. In marine ecosystems, the global decline in small pelagic fish (SPF) growth and survival capacities was linked to overfishing and climate change, but the underlying mechanisms remain elusive, although SPF play a central ecological role and sustain large fisheries. To address this issue, we combined a set of physiological markers (assessing digestive enzyme activity, oxidative, chronic, and nutritional stress) and environmental variables for sardine (Sardina pilchardus) in three environmentally contrasted areas surrounding the French coast. Overall, we found sardines with higher chronic stress, lower content in eicosapentaenoic acid (EPA), and lower digestive enzyme activity in the Gulf of Lions, an area marked by a 30% decline in sardine size-at-age and a strong adult overmortality. In contrast, sardines from the English Channel, where no such demographic decline is observed, exhibited better physiological conditions. Sardines appeared to be in poorer physiological health under warmer sea surface temperatures and lower phytoplankton concentrations. However, links between physiology and environmental variability were less clear in the Bay of Biscay, an area with similar growth and survival declines than in the Gulf of Lions. These findings highlight the critical impact of environmental factors on the physiological status and overall health of sardine populations but with global and local patterns of response, emphasizing the unique challenges faced by each population of this species
Effect of consumption temperature of whole milk on in vitro gastric digestion using a biomimetic digestion simulator
No full textInternational audienceThis study evaluates the effect of consumption temperature on the gastric digestion behaviour of whole milk using a dynamic in vitro model (NERDT™, computer-controlled biomimetic system). Human intragastric temperature profiles in response to cold, warm, and hot beverages were accurately reproduced to mimic the conditions encountered after consumption of milk at 4 • C, 37 • C and 60 • C. For comparison, control experiments were performed with milk at 37 • C without any pepsin addition. Results show that milk coagulated more rapidly within the stomach when consumed at 37 • C or 60 • C compared to 4 • C and 37 • C without pepsin. Moreover, the gastric emptying rate of milk proteins in the presence of pepsin was slower with milks at 37 • C and 60 • C compared with the milk at 4 • C. The hydrolysis of milk proteins also appeared to be temperature-dependant, with proteolysis increasing with higher milk temperatures towards the end of digestion. Regarding the fat fraction of milk, our data suggest that both hot (60 • C) and cold milk (4 • C) could plausibly increase the gastric emptying rate of milk fat, compared to a 37 • C milk, but further studies remain needed to verify this hypothesis. At the end of the experiments, the wet and dry masses of the residual gastric digesta was similar across the three conditions with pepsin, but significantly lower than in the absence of pepsin at 37 • C. This study enhances our understanding of how consumption temperature influences the kinetics of pepsin-induced milk coagulation and the subsequent gastric disintegration of dairy particles
Marine heatwaves deeply alter marine food web structure and function
No full textInternational audienceMarine heatwaves (MHWs) are becoming longer, more frequent and more intense in recent decades. MHWs have caused large-scale ecological impacts, such as coral bleaching, mass mortality of seagrass, fishes and invertebrates, and shifts in abundance and distribution of marine species.However, the implications of these MHW-induced impacts on marine species for the structure and functioning of marine food webs are not clearly understood. In this study, we use the EcoTroph-Dyn 15 ecosystem modelling approach to examine the impacts of MHWs occurring during the year's warmest month on the trophodynamics of marine ecosystems. EcoTroph-Dyn represents marine ecosystem dynamics at a spatial resolution of 1° longitude by 1° latitude and a temporal resolution of 14 days. We applied the model to simulate changes in trophodynamic processes, energy transfer and ecosystem biomass using daily temperature and monthly net primary production (NPP) that were derived from 20 satellite observation from 1998 to 2021. We compared and contrasted the simulated changes in biomass by trophic levels with results generated from temperature and NPP time series that had been filtered to remove MHWs. Our results show a significant decline in biomass between 1998 and 2021 specifically caused by MHWs. For example, in the Northeast Pacific Ocean, our model simulated a specific MHW decline in biomass of 8.7% ± 1.0 (standard error) in the region from 2013 to 2016. 25 Overall, MHW-induced biomass declines are more pronounced in the northern hemisphere and Pacific Ocean. Moreover, the MHW-induced declines in high trophic level biomass were larger than lower trophic levels and lasted longer post-MHW. Finally, this study highlights the need to integrate MHWs into modelling the effects of climate change on marine ecosystems. It shows that the EcoTroph approach, and especially its new dynamic version, provides a framework to understand more 30 comprehensively the implications of climate change for marine ecosystem structure and functioning.</p
Pilot-scale in situ assessment of desealing strategies under different pedo climatic conditions
No full textInternational audienceSoil sealing (i.e., covering the soil with impermeable material) is one of the main causes of soil degradation in Europe. Although the strongly negative consequences of sealing on the bio-physicochemical properties and the functioning of soils are known, very little work has so far been devoted to the evaluation of the potential for soil renaturation after unsealing. The DESSERT project (Desealing of soils, ecosystem services and territory resilience – 2020-2024) supported by the French Agency for Ecological Transition (ADEME) aimed at (i) acquiring knowledge on the quality, functioning and capacity of unsealed urban soils to provide ecosystem services, (ii) proposing a typology of unsealing processes, (iii) evaluating of the performances of different unsealing practices in terms of renaturation of cities, (iv) implementing of laboratory experiments for the optimization of soil management following unsealing processes, (v) implementing and monitoring over time of in situ pilot sites and (vi) contributing to decision support via the development and wide dissemination of a multi-attribute tool to assist in the design of urban soils unsealing projects.Within the framework of this project, in situ pilot scale plots were implement between November 2021 and March 2022 under three contrasted pedo climatic condition of Metropolitan France territory. For each site an impervious area of about 140 m2 was desealed (i.e. the surface impervious layer was removed) and separated into four subplots to test different soil management practices. Along an increasing intervention gradient the four modalities were: i) no further action on the soil; ii) decompaction and mixing of the top 30 cm; iii) decompaction, addition and mixing of green waste compost in the top 30 cm in a 1:3 ratio; iv) excavation of the top 30 cm and replacement with a mixture of “natural” topsoil and compost in a 1:3 ratio. All treatments and sites were then sown with the same mixture of ten herbaceous species in spring 2022. Soil evolution (composition, functioning) was then analysed with regular sampling and in situ probes (temperature, humidity) and vegetation cover evolution was followed in terms of diversity, surface coverage and biomass production
Comprehensive annotation of olfactory and gustatory receptor genes and transposable elements revealed their evolutionary dynamics in aphids
No full textInternational audienceGene duplication and transposable elements (TEs) are major drivers of genomic innovation that can fuel adaptation. While the roles of duplication and TE-driven diversification are documented in plant pathogens, they remain insufficiently explored in insect pests such as aphids, where olfactory (OR) and gustatory receptor (GR) genes are key to host recognition. We analyzed 521 OR and 399 GR genes, alongside TEs, across 12 aphid genomes with varying host ranges. Aphid lineages with broader host ranges exhibited higher evolutionary rates, driven by gene family expansions linked to host interaction, including lipid metabolism, immune function, and transposase activity. OR and GR genes evolved through proximal and tandem duplications and were shaped by diversifying selection, with bursts of positive selection followed by prolonged purifying selection, consistent with adaptation to novel hosts. Younger TEs were significantly enriched near OR genes compared to GRs and other genomic regions, suggesting a catalytic role of TEs in their diversification. However, OR proteins encoded by TE-associated ORs exhibited reduced functional potential. In contrast, GR proteins encoded by TE-associated GRs retained signatures of adaptation, as inferred from deep learning models predicting functionally important protein regions. These findings suggest that TE activity may facilitate functional innovation in GRs while alleviating constraints or pseudogenization in ORs. This study reveals how duplication, selection, and TE dynamics shape gene evolution in insect pests. It also provides the first chromosome-scale genome assembly of Dysaphis plantaginea, with comprehensive annotations and functional predictions of OR/GR genes, bridging adaptive evolution with mechanistic insights
How many prey does a predator eat in a day?
No full textInternational audienceVery few interactions are as decisive as trophic interactions to understand the structure and dynamics of ecological communities. Initiated as such in the early days of ecological research [Elton 1927, Lindeman 1942, Odum 1968], works on food webs have recently benefited from the development of molecular analyses [Pereira et al. 2023], especially DNA-based analyses such as PCR-diagnostic or Metabarcoding. Applied to gut content or faeces indeed, molecular analyses greatly facilitate the description of food webs, and can provide novel insights on diet diversity and food references. However, despite commendable efforts [e.g. Zhang et al. 2007a], molecular analyses remain largely qualitative (presence/absence of prey) [Furlong et al. 2015]. Furthermore, molecular evidences of prey consumption decay at a different rate for each predator-prey pair, which impedes the quantification of prey consumption rates based on prey detection frequency. Previous works circumvented this issue by adjusting detection frequencies with prey DNA half-lives [Greenstone et al. 2010, Uuiterwaal et al. 2020] calibrated on voracity experiments [Greenstone et al. 2014], allowing the inference of relative consumption rates. In line with those works, we propose a Hierarchical Bayesian Model that integrates field detection frequencies and voracity data in a novel mechanistic framework to infer posterior probability distributions of key parameters encompassing possible uncertainties. By explicitely discriminating predation and digestion, the model provides an estimate of the slope and intercept of the digestion curve and an estimate of the number of preys consumed by a predator in a day, hereby referred to as predation intensity. At second order of hierarchy, moreover, each parameter is broken down into a prey, a predator and a pair effect which allows information to be leveraged from widely observed species to inform and improve estimates on rare species. Through a case study with 27 carabid beetles’ species preying on 5 types of preys in agricultural fields (wheat and beet), we use our model to investigate the main drivers of predation intensity at species scale (i.e. traits such as predator diet or size) and at community scale (i.e. characteristics such as community size or alpha diversity)
A Salivary Effector of the Pea Aphid Interacts with Pea Proteins and Enhances Its Performance on the Host Plant
No full textInternational audienceAphids have intricate interactions with their host plants, but the molecular mechanisms behind these interactions remain largely unknown. The pea aphid Acyrthosiphon pisum is a legume specialist, which forms a complex of several biotypes, each specialized in feeding on a few legume species. Aphids inject a cocktail of salivary effector proteins into plants to suppress plant immunity and promote their performance such as fecundity. Previous studies showed that subsets of salivary effector genes of A. pisum are differentially expressed between the pea- and alfalfa-adapted biotypes. We hypothesized that the salivary effector genes that are important for A. pisum to feed on pea (Pisum sativum) are highly expressed in pea-adapted biotype compared to non-adapted ones and selected such genes for functional characterization. We have examined ten candidate genes and found that expression of the salivary gene LOC100159932 (Ap4) in pea leaves increased the fecundity of the A. pisum pea biotype. A yeast two hybrid screening using Ap4 as a bait identified two pea proteins named PsBPL1 and PsBPL2 that showed high homology with Arabidopsis BPL (Binding Partner of ACD11-Like) proteins, which are conserved in plants and fungi and known to be involved in plant immunity. GFP-tagged Ap4 proteins produced puncta in Nicotiana benthamiana cytoplasm and a bimolecular fluorescence complementation experiment confirmed the interaction of Ap4 and PsBPL1 and PSBPL2 in planta. These results highlight Ap4's role as an effector and suggest the involvement of BPL proteins in pea-aphid interactions
Detection of soil management practices using Sentinel-1 time series: the challenges raised by the diversified management sequences in vineyards
No full textInternational audienceCharacterization of soil management strategies in the complex agroecosystems of vineyards is crucial to evaluate their impact on vineyards soil health, particularly in the context of increasing soil threats posed in semi-arid environments [1], [2], [3], [4]. This study evaluates the potential of Sentinel-1 (S1) radar times series to detect soil management practices in Spanish vineyards. Two trellis-trained vineyards plots (ca. 4 ha each) located in the Toledo province (Spain) were studied, each subjected to a distinct soil management practice: conventional tillage (TILL) and a cover cropping system (CC), respectively. A farmer survey was conducted to thoroughly document the sequence, timing, and spatial distribution of management operations carried out between October 2020 and August 2024. A methodology based on S1 radar signal change detection was applied to detect soil surface roughness associated with these practices. The survey data served as a reference to evaluate the accuracy of the S1-derived detections. Results revealed a very high degree of variability in vineyards management practices, in terms of type, spatial distribution and frequency within these fields. Despite such diversified management sequence, satellite-based detection was effective on average, over more than 60% of the plot surface area, for tillage for both TILL and CC plots, weed control and rolling for only CC plot. Additionally, mechanical pruning was successfully detected in the TILL plot. Our further research will explore the integration of S1 radar data with S2 optical imagery to refine this detection and assessment of soil management practices in viticultural systems
Shrimp Hydrolysate-Based Palatability Enhancer: A Circular Economy and Cost-Effective Strategy to Reduce Fish in Fish Out Ratio in Marine Fish Species
No full textInternational audienceReducing the reliance of the aquaculture industry on wild fish resources remains a key challenge. Generally obtained from food coproducts, protein hydrolysates have emerged as promising functional and sustainable protein sources that can help compensate for the limitations of alternatives to marine proteins. In this study, we evaluated their use as a palatability enhancer (PE) by top-coating them directly on the feed, as a liquid and at low dose. We tested a PE made primarily from a shrimp liquid hydrolysate, as a cost-effective dietary solution to replace significant amounts of fish meal (FM) with plant proteins in juvenile red sea bream diets. The experimental feeds consisted in a high FM diet (HFM, 30% FM), a low FM diet (LFM, 15% FM) and two additional diets with 2% PE top-coated (HFM+PE and LFM+PE). Six replicate tanks, each containing fish weighing 27.2 ± 0.2 g, were provided with one of the test diets twice daily until apparent satiety for a duration of 15 weeks. Half of the 2 tanks were exposed to an intermittent stress consisting in a 1 min net-chasing, 1 hour before their first meal. After the nutritional trial, individuals were subjected to an Edwarselia tarda challenge through injections. The basal diets, LFM and HFM, achieved comparable growth and feed efficiency. The use of LFM, therefore, mechanically reduced wild fish use by 25% if referring to the eFIFO index (Kok et al., 2020). PE supplementation in both diets resulted in enhanced fish growth and health performance, and improved feed use. Consequently, we estimated that PE use can significantly, and additionally, reduce by 6% the use of wild fish biomass in these conditions. The beneficial effects of PE on the growth performance were stable despite the stress challenge, which led however to overall strong reduction in growth performances in all groups. Survival was significantly increased by PE addition in response to the bacterial challenge compared to the LFM diet. All these results were supported by underlying physiological results. We concluded that liquid hydrolysate PE represent a great potential for feed formulators to cost-effectively reduce pressure on wild resources, while maintaining high performance of their feed
Agriculture, aquaculture et pêche : impacts des modes de production labellisés sur la biodiversité. Rapport scientifique de l'étude
No full textLa loi Climat et résilience de 2021 a instauré la mise en place d’un affichage environnemental sur les produits alimentaires afin d’informer les consommateurs du coût environnemental de leurs achats. La construction de cet affichage a suscité un important travail méthodologique ouvert aux acteurs. Un bilan intermédiaire a souligné la difficulté à appréhender toutes les dimensions de la biodiversité. C’est dans ce cadre que les ministères en charge de la transition écologique, et de l’agriculture et de l’alimentation, ainsi que l’ADEME, ont sollicité INRAE et l’Ifremer courant 2022 pour mieux documenter ce volet biodiversité, en se focalisant sur les pratiques de production. Afin d’éclairer plus largement les politiques publiques, les pouvoirs publics ont choisi de s’appuyer sur les labels dont les cahiers des charges certifient des pratiques et parce que leur développement les place au cœur de nombreux débats sur les relations entre production et consommation durables. L’étude, intitulée « BiodivLabel », a été menée par un comité pluridisciplinaire d’experts scientifiques issus d’organismes publics de recherche et d’enseignement supérieur