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The current management of rodent pest populations is based on second-generation anticoagulant rodenticides (SGAR). These molecules, of which difethialone is part, are much more efficient than the first generation. Nevertheless, this efficiency comes with a major drawback, SGARs are tissue persistent that increases the exposure of rodent predators to them. According to its chemical structure, difethialone has four stereoisomers, whose specific inhibition potency and pharmacokinetic have never been described and might be useful to design new eco-friendly rodenticides. The study aimed to investigate the ability to inhibit anticoagulant target enzyme (VKORC1) and the pharmacokinetics in rats of the four difethialone stereoisomers in rats. We show that stereoisomers are all highly efficient to inhibit VKORC1 activity, but they have distinct initial half-life with 6.0 h, 25.4 h, 69.3 h, and 82.3 h for, respectively, E4-trans, E2-cis, E1-trans, and E3-cis stereoisomer. These results open the way of the development of eco-friendly and efficient rodenticide by mixing some of these stereoisomers. Preferential incorporation of the E4-trans stereoisomer (high inhibitory VKORC1 potency, relatively shorter liver half-life) into difethialone rodenticides baits might result in a more eco-friendly product than current commercially available difethialone formulations. In addition, we put forward modelling to help design bait according to the circumstance of use (presence of non-target species, food competition, etc.) by modulating the theorical AUC and and the theorical concentration of the product at the death of the rodent pest. Thus, this modeling might allow to diminish the use of laboratory animal in assay. Difethialone stereoisomers are potent inhibitors of VKORC1 enzyme activity. Difethialone stereoisomer initial half-lives range from 6 to 69.3 h. E1-trans and E3-cis initial half-lives are similar and greater than other stereoisomers. Modeling can be used to refine the bait formulation process and to diminish the use of laboratory animals.

Thus far, no long-term in situ observation of planktonic biomass have been undertaken to optimize the black-lip pearl oyster aquaculture in the remote Tuamotu atolls. The feasibility of using data from the OLI sensor onboard Landsat-8 satellite to determine chlorophyll a concentrations (Chla) in a deep atoll, Ahe, was then assessed over the 2013–2021 period using 153 images. Validations with in situ observations were satisfactory, while seasonal and spatial patterns in Chla were evidenced within the lagoon. Then, a bioenergetic modelling exercise was undertaken to estimate oyster life-history traits when exposed to the retrieved Chla. The outputs provide spatio-temporal variations in pelagic larval duration (11.1 to 30.6 days), time to reach commercial size (18.8 to 45.3 months) and reproductive outputs (0.5 to 1.7 event year−1). This first study shows the potential of using remote sensing to monitor the trophic status of deep pearl farming lagoons and help aquaculture management.

Anticoagulant rodenticides (ARs), particularly second-generation compounds (SGAR), are known to be a potential threat to unintended species due to their tissue persistence. The liver is the storage tissue of ARs and is a matrix of choice in diagnosing exposure and intoxication of non-target fauna. However, it is only available on dead animals. Blood and faeces can be used on living animals. These two biological matrices were compared in terms of their relevance to exposure to ARs. In addressing this question, we compared the faecal, plasma and liver concentrations of bromadiolone, one of the SGAR frequently implicated in wildlife exposure. We studied this comparison at the individual level and at the population level, considering three influencing factors: dose, sex and time. Our findings demonstrate that faecal analyses are more valuable than plasma analyses for monitoring AR exposure of domestic and wild animals, even if faecal concentrations cannot be correlated with liver concentrations.

The ecotoxicity of anticoagulants used for rodent pests' management is a major concern, particularly with second generation anticoagulants, which are more persistent in the body of rodents and therefore more likely to cause secondary exposure in their predators. One of the solutions envisaged to mitigate this risk is to use stereoisomers of these anticoagulants, each of which has particular pharmacokinetics. However, the few studies published to date have considered only one species and one sex. Here, we study the pharmacokinetics of the 4 stereoisomers of 3.4 mg/kg of difethialone in rats (Rattus norvegicus) and 3 mg/kg in mice (Mus musculus) in both sexes and propose a model to choose the optimal stereoisomer efficacy/ecotoxicity mixture for the management of all these animals. Our results show that while the most persistent stereoisomer (E3-cis) is common to both species and sexes, the pharmacokinetics of the other stereoisomers show marked differences between sexes and species. Thus, the area under curve (AUC) of E4-trans in male rats is four times lower than in females or mice, making it a priori unusable in male rats. Conversely, our modeling seems to show that the E1-trans stereoisomer seems to offer the best compromise AUC persistence. In conclusion, we highlight that studies on anticoagulants must necessarily integrate research on the effect of gender and species both on efficacy and with regard to the ecotoxicity of these molecules.

The ability to efficiently implement ecosystem-based fisheries management is largely dependent on data availability. As invertebrates are not included in routine monitoring programmes, data should be collected by different approaches. We assessed whether fish could be suitable biological samplers of benthic invertebrates in the Eastern English Channel by comparing spatial distributions of Galatheidae, Portunidae and Porcellanidae found in digestive tracts (DTs) from a fish survey (Channel Ground Fish Survey), and in a dedicated benthos survey (Eastern English Channel Benthic Survey, ECBS). We found a significant spatial match between the distributions of Porcellanidae, Galatheidae and Portunidae found in fish DTs, and the ECBS occurrence-based maps. The strongest overlap was found for Galatheidae. Spatial distributions of Porcellanidae based on fish DTs better overlapped those derived from dedicated benthos surveys when we assumed these prey to also be consumed in the neighbouring spatial units to where fish were sampled. This might reflect the relatively high mobility of the dominant predators of Porcellanidae (e.g. Mustelus asterias, Scyliorhinus canicula). Overall, this study demonstrated that fish diet sampling can provide valuable information on the spatial distribution of benthic organisms.

International audience; The widespread use of pesticides to control agricultural pests is a hot topic on the public scene of environmental health. Selective pest control for minimum environmental impact is a major goal of the environmental toxicology field, notably to avoid unintended poisoning in different organisms. Anticoagulant rodenticides cause abnormal blood coagulation process; they have been widely used to control rodents, allowing inadvertent primary and secondary exposure in domestic animals and non-target predatory wildlife species through direct ingestion of rodenticide-containing bait or by consumption of poisoned prey. To report toxic effect, the most common approach is the measurement of liver or plasma residues of anticoagulant rodenticides in dead or intoxicated animals showing clinical symptoms. However, one major challenge is that literature currently lacks a hepatic or plasma concentration threshold value for the differentiation of exposure from toxicity. Regarding the variation in pharmacology properties of anticoagulant rodenticides inter- and intra-species, the dose-response relationship must be defined for each species to prejudge the relative risk of poisoning. Beyond that, biomarkers are a key solution widely used for ecological risk assessment of contaminants. Since anticoagulant rodenticides (AR) have toxic effects at the biochemical level, biomarkers can serve as indicators of toxic exposure. In this sense, toxicological knowledge of anticoagulant rodenticides within organisms is an important tool for defining sensitive, specific, and suitable biomarkers. In this review, we provide an overview of the toxicodynamic and toxicokinetic parameters of anticoagulant rodenticides in different animal species. We examine different types of biomarkers used to characterize and differentiate the exposure and toxic effects of anticoagulant rodenticide, showing the strengths and weaknesses of the assays. Finally, we describe possible new biomarkers and highlight their capabilities.

Wild raptors are widely used to assess exposure to different environmental contaminants, including anticoagulant rodenticides (ARs). ARs are used on a global scale for rodent control, and act by disruption of the vitamin K cycle that results in haemorrhage usually accompanied by death within days. Some ARs are highly persistent and bioaccumulative, which can cause significant exposure of non-target species. We characterized AR exposure in a heterogeneous sample of dead raptors collected over 12 years (2008–2019) in south-eastern France. Residue analysis of 156 liver samples through LC-MS/MS revealed that 50% (78/156) were positive for ARs, with 13.5% (21/156) having summed second-generation AR (SGAR) concentrations >100 ng/g ww. While SGARs were commonly detected (97.4% of positive samples), first-generation ARs were rarely found (7.7% of positive samples). ARs were more frequently detected and at greater concentration in predators (prevalence: 82.5%) than in scavengers (38.8%). Exposure to multiple ARs was common (64.1% of positive samples). While chlorophacinone exposure decreased over time, an increasing exposure trend was observed for the SGAR brodifacoum, suggesting that public policies may not be efficient at mitigating risk of exposure for non-target species. Haemorrhage was observed in 88 birds, but AR toxicosis was suspected in only 2 of these individuals, and no difference in frequency of haemorrhage was apparent in birds displaying summed SGAR levels above or below 100 ng/g ww. As for other contaminants, 17.2% of liver samples (11/64) exhibited Pb levels compatible with sub-clinical poisoning (>6 μg/g dw), with 6.3% (4/64) above the threshold for severe/lethal poisoning (>30 μg/g dw). Nine individuals with Pb levels >6 μg/g dw also had AR residues, demonstrating exposure to multiple contaminants. Broad toxicological screening for other contaminants was positive for 18 of 126 individuals, with carbofuran and mevinphos exposure being the suspected cause of death of 17 birds. Our findings demonstrate lower but still substantial AR exposure of scavenging birds compared to predatory birds, and also illustrate the complexity of diagnosing AR toxicosis through forensic investigations.

Arenicola marina (Annelida Polychaeta) is a harvested ecosystem engineer inhabiting galleries within soft-sediment foreshores from the Mediterranean to the Arctic. It displays a typical distribution pattern on most foreshores, with the juveniles inhabiting the mediolittoral shore and migrating to the infralittoral shore while growing. In this study, we have characterized the shore migrations of a temperate population of A. marina and estimated its potential individual growth and reproduction under different migration scenarios using a Dynamic Energy Budget model. A sand temperature model was developed in order to predict the temperature experienced by lugworms according to the depth of their galleries and their bathymetric level. The food availability and the associated scaled functional response were estimated from in situ growth data and associated nitrogen content and chlorophyll-a concentration (Chla) data. The metabolic response of lugworms to temperature (temperature tolerance range, related Arrhenius temperatures) was assessed from literature data. The sand temperature model outputs did not explain alone spatial differences in individual growth and reproduction. However, an increase of food availability with bathymetry, with Chla as a proxy, well explained growth and reproduction. For now, the temperature hypothesis is discarded but other factors (desiccation or hypoxia) should be considered in future studies.

WOS:000691601000007; International audience; This study addresses the temporal variability of couplings between pelagic and benthic habitats for fish assemblages at five periods in a shallow epicontinental sea, the Eastern English Channel (EEC). Organic matter fluxes fueling fish assemblages and the relative contribution of their different sources were assessed using stable isotope analysis and associated isotopic functional metrics. Couplings between benthic and pelagic realms appeared to be a permanent feature in the EEC, potentially favored by shallow depth and driven by the combination of two trophic processes. First, trophic interactions exhibited plasticity and revealed resource partitioning. Second, changes in the composition of fish assemblages did not impact benthic-pelagic couplings, as most dominant species were generalists during at least one time period, allowing complete use of available resources. Examining both unweighted and biomass-weighted indices was complementary and permitted a better understanding of trophic interactions and energy fluxes.

International audience; Anticoagulant rodenticides are widely used for rodent control in agricultural and urban settings. Their intense use can sometimes result in accidental exposure and even poisoning of livestock. Can milk, eggs or meat derived from such accidently exposed animals be consumed by humans? Data on the pharmacokinetics of chlorophacinone in milk of accidently exposed ewes were used to estimate the risk associated with its consumption. Three days after accidental ingestion, chlorophacinone was detected in plasma of 18 ewes, with concentrations exceeding 100 ng/mL in 11 animals. Chlorophacinone was detected in milk on day 2 post-exposure and remained quantifiable for at least 7 days in milk of these 11 ewes. Concentrations in milk were much lower than in plasma and decreased quickly (mean half-life of 2 days). This study demonstrated dose-dependent mammary transfer of ingested chlorophacinone. Variation in prothrombin time (PT) on Day 3 suggested that some of the ewes that ingested chlorophacinone may have been adversely affected, but PT did not facilitate estimation of the quantity of chlorophacinone consumed. Using safety factors described in the literature, consumption of dairy products derived from these ewes after a one-week withdrawal period would pose low risk to consumers.

Anaphylaxis is a condition that warrants an observation period after symptoms resolution to detect rare but life-threatening delayed complications. There is a need for evidence to identify patients who would benefit from prolonged observation time. The purpose of this review was to identify factors that may influence the need for longer observation in the emergency department.PubMed, Embase, EBM Review, and Cochrane Library were searched using controlled vocabulary and keywords to cover all relevant data. Titles, abstract, and full text were reviewed for inclusion and exclusion criteria. Data were extracted from the included articles regarding case definitions, prognosis, treatment and time factors, and recommended observation time. Factors linked to observation time or complications were tabulated and compared between studies.The search retrieved 2443 citations of which 49 were included. Twenty-one were primary studies and were used to identify factors influencing observation time or complications. Biphasic anaphylaxis was the only adverse event that warranted prolonged observation. The five risk factors often associated with biphasic reactions were time to first epinephrine, history of anaphylaxis, symptom severity, number of epinephrine doses, and unknown trigger. Biphasic reactions happened mostly within the first 72 h with most severe reactions occurring earlier than the milder ones. Heterogeneity in the definition of biphasic anaphylaxis made comparisons challenging.Observation time should be based on the provider's best estimation of the risk of biphasic anaphylaxis, although no single factor can predict their occurrence. The identified factors will allow the development of an early discharge screening tool.RéSUMé: OBJECTIF: L’anaphylaxie est une condition qui mérite une période d’observation après la disparition des symptômes pour détecter des complications retardées rares, mais potentiellement mortelles. Il est nécessaire de trouver des preuves pour identifier les patients qui bénéficieraient d’une période d’observation prolongée. Le but de cet examen était d’identifier les facteurs qui pourraient influencer la nécessité d’une période d’observation plus longue aux urgences. MéTHODES: PubMed, Embase, EBM Review et Cochrane Library ont été recherchés au moyen d’un vocabulaire contrôlé et des mots-clés pour couvrir toutes les données pertinentes. Les titres, le résumé et le texte intégral ont été examinés pour les critères d’inclusion et d’exclusion. Les données concernant les définitions de cas, le pronostic, le traitement et la durée de traitement, et la période d’observation recommandée ont été extraites des articles inclus. Les facteurs liés à la période d’observation ou aux complications ont été présentés sous forme de tableau et comparés entre les études. RéSULTATS: La recherche a permis de récupérer 2443 citations dont 49 ont été incluses. Vingt et un étaient des études primaires et ont été utilisées pour identifier les facteurs influençant la période d’observation ou les complications. L’anaphylaxie biphasique était le seul événement indésirable qui méritait une observation prolongée. Les cinq facteurs de risque souvent associés aux réactions biphasiques étaient le délai de la première épinéphrine, les antécédents d’anaphylaxie, la gravité des symptômes, le nombre de doses d’épinéphrine et le déclencheur inconnu. Les réactions biphasiques se sont produites principalement dans les 72 premières heures avec les réactions les plus graves se présentant plus tôt que les réactions plus légères. L’hétérogénéité de la définition de l’anaphylaxie biphasique a rendu les comparaisons difficiles. CONCLUSIONS: La période d’observation doit être basée sur la meilleure estimation du risque d’anaphylaxie biphasique fournie par le professionnel de la santé, bien qu’aucun facteur unique ne puisse prédire son apparition. Les facteurs identifiés permettront le développement d’un outil de dépistage pour les sorties précoces de l’hôpital.

International audience; All vitamin K antagonist active substances used as rodenticides were reclassified in 2016 by the European authorities as active substances "toxic for reproduction", using a "read-across" alternative method based on warfarin, a human vitamin K antagonist drug. Recent study suggested that all vitamin K antagonist active substances are not all teratogenic. Using a neonatal exposure protocol, warfarin evokes skeletal deformities in rats , while bromadiolone, a widely used second-generation anticoagulant rodenticide, failed to cause such effects. Herein, using a rat model we investigated the mechanisms that may explain teratogenicity differences between warfarin and bromadiolone, despite their similar vitamin K antagonist mechanism of action. This study also included coumatetralyl, a first-generation active substance rodenticide. Pharmacokinetic studies were conducted in rats to evaluate a potential difference in the transfer of vitamin K antagonists from mother to fetus. The data clearly demonstrate that warfarin is highly transferred from the mother to the fetus during gestation or lactation. In contrast, bromadiolone transfer from dam to the fetus is modest (5% compared to warfarin). This difference appears to be associated to almost complete uptake of bromadiolone by mother's liver, resulting in very low exposure in plasma and eventually in other peripheric tissues. This study suggests that the pharmacokinetic properties of vitamin K antagonists are not identical and could challenge the classification of such active substances as "toxic for reproduction".

Le chien et le chat sont des carnivores au sens phylogénique (présence de carnassières). Pour ce qui est de l'alimentation en tant que telle, le point est plus complexe. Le chien est couramment présenté comme un carnivore opportuniste et le chat comme un carnivore strict. Ce terme de carnivore ne signifie pas que le régime de ces animaux doit être exclusivement centré sur une alimentation carnée, mais qu'un certain nombre de nutriments nécessaire à leur physiologie ne se trouve généralement que dans des produits carnés. Cette distinction est essentielle. De plus, produit carné ne signifie pas viande, un régime entièrement composé de viande est, de façon certaine, déséquilibré et conduit à de graves carences nutritionnelles. De l'avis de l'auteur, si le chien n'est pas un carnivore strict, il ne peut pas être considéré comme un omnivore du fait de ses besoins importants en nutriments d'origine animale : arginine, taurine, vitamine D. De plus, dans la pratique vétérinaire, l'objectif n'est pas uniquement de maintenir l'animal en vie, mais aussi de lui garantir la meilleure qualité de vie en prévenant autant que possible les affections chroniques. Pour ce faire, le but de la nutrition est de s'assurer que les apports en énergie et en nutriments de l'animal sont en accord avec ses besoins spécifiques définis par son espèce, son cadre de vie et les affections dont il peut souffrir. Ce chapitre présente un rappel des points essentiels de la physiologie et du comportement alimentaire des carnivores domestiques, avant d'aborder les besoins en énergie et en nutriments. Dans ce chapitre est présenté un système d'analyse des besoins, celui utilisé dans le logiciel VetNutri et dans le reste de ce livre. Plus que l'aspect calculatoire, qui peut être délégué à une machine, la philosophie des besoins et leurs limites, et les grandes notions comme le besoin énergétique à l'entretien sont à acquérir, afin de pratiquer la nutrition clinique et de pouvoir interpréter les analyses.

International audience; This study aims at (1) experimentally estimating first sexual maturation of the European sardine S. pilchardus, (2) using the results to calibrate existing bioenergetic models. During the 183 days-experiment, fish growth and body condition were assessed by biometry, and gonads were weighed when present. Age, wet weight and total length at first maturity were estimated at 262 days, 10.79 ± 0.75 g, and 11.26 ± 0.21 cm, respectively. Including these traits in biphasic Von Bertalanffy models did not significantly improve simulations for either length or weight data, meaning that energy allocation was not impacted by these traits. The implementation of the results in the Dynamic Energy Budget (DEB) calibration procedure strengthened the parameter set of the existing model, but resulted in significant changes in the energy allocation. Our results are a first step that will allow the design of new experiments to further quantify maturation and reproduction rates in diverse environmental conditions, consolidating DEB model calibration

Place: Amsterdam Publisher: Elsevier WOS:000579484600004; Integrated Multi-Trophic Aquaculture (IMTA) systems have been designed to optimize nutrient and energy use, to decrease waste, and to diversify fish-farm production. Recently, the development of detritivorous aquaculture has been encouraged, as detrivores can consume organic particulate matter, reducing benthic eutrophication and the environmental footprint of aquaculture. To this end, the polychaete Hediste diversicolor is a promising species due to its broad feeding behaviour and its resistance in a wide range of environments. In this study, an existing Dynamic Energy Budget (DEB) model of H. diversicolor was used to predict the ragworm's metabolic processes in various environmental conditions and to estimate its bioremediation capacity in an aquaculture context. First, the scaled functional response (f) was calibrated in a 98-day growth experiment with two types of food (Fish faeces and Fish feed). Then, we further validated the model using data on the ammonia excretion and oxygen consumption of individuals fed with fish faeces at four different temperatures using the previously calibrated f. Overall, we found that the DEB model was able to correctly predict the experimental data (0.51 \textless MRE \textless0.80). Lastly, different environmental scenarios of seawater temperatures and assimilation rates were compared. The bioremediation potential of H. diversicolor was estimated based on cumulated assimilation rates, which could represent 75-289 kg of fish waste year(-1) for a 100 m(2) ragworm farm (3700 ind. m(-2)). These findings suggest that the DEB model is a promising tool for further IMTA development and management.

Par défiance des aliments industriels, à la suite d'informations trouvées sur internet, à des croyances, à une réflexion éthique.. . les propriétaires d'animaux se tournent, pour une part non négligeable, vers des rations que nous qualifierons de non conventionnelles. Cette qualification est mal définie, et regroupe plusieurs grands « types" de rations, des rations crues aux rations sans céréales en passant par les rations végétariennes. Mais, l'un des points communs à toutes ces rations est la motivation du propriétaire. Ainsi, dans le cadre des rations non conventionnelles, il y a une recherche d'alternative aux rations industrielles ou ménagères, non pas avec comme premier objectif d'avoir un apport équilibré en nutriments, mais de répondre à une certaine croyance ou orthodoxie alimentaire. Cette doctrine peut trouver son origine dans la recherche d'une alimentation plus saine ou plus adaptée à l'image que le propriétaire se fait de son animal. Ainsi, dans l'accompagnement et le conseil du propriétaire, dans l'intérêt de l'animal, il est essentiel de comprendre la base des motivations du propriétaire, afin d'identifier les leviers d'action. En effet, la motivation derrière le choix d'une ration n'est pas toujours rationnelle. Et quand elle l'est, le raisonnement sous-jacent n'est pas toujours soutenu par des preuves scientifiques, mais, le plus souvent, par des sophismes et arguments fallacieux. La discussion avec le propriétaire peut aussi être perturbée par un effet Dunning-Kruger. De plus, il existe un fort engagement de la part des propriétaires et des promoteurs de ce genre de pratique tenant de la conviction et laissant peu de place à l'argumentation. Par exemple, l'un des premiers articles sur l'équilibre des rations BARF en 2001 a fait l'objet de nombreuses lettres à l'éditeur. L'un des arguments les plus avancés est que les auteurs de ces études sont "contre" ces pratiques non conventionnelles, déplaçant ainsi la discussion du registre scientifique à celui d'opinion. De la vision de l'auteur, le conseil et l'accompagnement du propriétaire doivent se baser sur son information par la présentation de preuves apportées par la science, sans juger, ni nécessairement tenter de convaincre, ce qui est souvent contre-productif. Ce chapitre présente les deux types de rations non conventionnelles les plus communes, celles à base de viande crue et le sans céréales.

International audience

International audience; Carbon (delta C-13) and nitrogen (delta N-15) stable isotope analyses are used in marine ecology to study trophic relationships and migrations of species since they reflect dietary sources consumed which may vary geographically. However, better estimations of isotope incorporation rates and trophic discrimination factors (TDF) under controlled conditions are required. Moreover, variability of isotope incorporation rates and TDF among and within populations has been poorly described, especially in fish scales, whereas the use of non-lethal method is becoming a standard. This study aimed to experimentally assess whether carbon and nitrogen isotope incorporation rates (lambda C and lambda N, respectively) and TDF of scales vary in the European sea bass (Dicentrarchus labrax) among (1) Atlantic, West Mediterranean and East Mediterranean populations, (2) sexes and (3) individuals. Fish were reared under controlled conditions and switched from a diet 1 to a diet 2 with different delta C-13 and delta N-15 values. Scales were sampled repeatedly on 16 fish within the three populations, from the day of diet change (day 0) to the end of the experiment (day 217). Isotope incorporation rates of scales and TDF were determined using a time-dependent model. Isotopic carbon and nitrogen half-lives (t(50)C and t(50)N) were similar among the three populations but males had significantly lower t(50)C and t(50)N than females (29 +/- 2 and 35 +/- 2 days vs. 53 +/- 7 and 80 +/- 11 days, respectively). Females had higher growth rates but lower catabolic rates than males. Variability of lambda C . and lambda N was large within sexes: t(50)C ranged from 17 to 159 days and t(50)N ranged from 18 to 342 days among individuals. Thus, variability between sexes and among individuals must be considered to avoid misinterpretation in field-based studies. For the 48 fish, TDF were 4.91 +/- 0.03 and 2.46 +/- 0.06 parts per thousand for carbon and nitrogen, respectively, and similar between sexes and among populations. Besides, TDF varied among individuals from 2.95 to 5.59 parts per thousand and from 0.93 to 3.55 parts per thousand for carbon and nitrogen, respectively. Empirical mixing models were run to estimate how different TDF influenced estimation of the contributions of food sources to diet of their consumer. The output differed considerably when using TDF from fish literature or those estimated herein, which confirms that a tissue-specific TDF must be used to avoid misinterpretation in field-based studies. Individual variation in TDF did not, however, influence estimation of the contributions of food sources, confirming that scales are a valid tissue for non-lethal sampling.

Arenicola spp. are marine benthic polychaetes dug for bait by anglers. Without regulation, this activity can lead to the decrease of lugworms' population meanwhile affecting the physical characteristics of the beach and the biodiversity. Here, we identified through morphology and genetics two species of lugworms, Arenicola marina and A. defodiens, within a Marine Protected Area of the Eastern English Channel (France). For each species, abundance and spatial distribution were assessed using a stratified random sampling and interpolation at four studied sites, as well as some life-history traits. These data were compared to lugworms' collection data to estimate its sustainability and to provide potential management measures. At one site, A. marina was present in large numbers on the higher and middle shore, whereas A. defodiens occupied the lower shore. At the other sites, both species co-occurred on the lower shore, and A. marina individuals were less numerous and lacking recruits. Spawning periods for A. marina occurred in early autumn and in late autumn for A. defodiens. The size at first maturity of A. marina was at 3.8 cm of trunk length (between 1.5 and 2.5 years old). One site (Au) appeared in need for management when linking abundance data with bait collection, where harvest of both species represented ∼14% of the total amount of lugworms and was above the carrying capacity of the beach for A. marina. The retail value associated to lugworm harvesting within the MPA was estimated at the same level as the shrimp retail value. Our results highlight the need for some fishery regulations.

The link between harmful algal blooms, phytoplankton community dynamics and global environmental change is not well understood. To tackle this challenging question, a new method was used to reveal how phytoplankton communities responded to environmental change with the occurrence of an harmful algae, using the coastal waters of the eastern English Channel as a case study. The great interannual variability in the magnitude and intensity of Phaeocystis spp. blooms, along with diatoms, compared to the ongoing gradual decrease in anthropogenic nutrient concentration and rebalancing of nutrient ratios; suggests that other factors, such as competition for resources, may also play an important role. A realized niche approach was used with the Outlying Mean Index analysis and the dynamics of the species’ realized subniches were estimated using the Within Outlying Mean Indexes calculations under low (L) and high (H) contrasting Phaeocystis spp. abundance. The Within Outlying Mean Indexes allows the decomposition of the realized niche into realized subniches, found within the subset of habitat conditions and constrained by a subset of a biotic factor. The two contrasting scenarios were characterized by significantly different subsets of environmental conditions and diatom species (BV-step analysis), and different seasonality in salinity, turbidity, and nutrients. The subset L environmental conditions were potentially favorable for Phaeocystis spp. but it suffered from competitive exclusion by key diatom species such as Skeletonema spp., Thalassiosira gravida, Thalassionema nitzschioides and the Pseudo-nitzchia seriata complex. Accordingly, these diatoms species occupied 81% of Phaeocystis spp.'s existing fundamental subniche. In contrast, the greater number of diatoms, correlated with the community trend, within subset H exerted a weaker biological constraint and favored Phaeocystis spp. realized subniche expansion. In conclusion, the results strongly suggest that both abiotic and biotic interactions should be considered to understand Phaeocystis spp. blooms with greater consideration of the preceeding diatoms. HABs needs must therefore be studied as part of the total phytoplankton community.

Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and quality of underwater light (i.e. light climate) is essential to understand primary production. A wavelength-dependent photoacclimation strategy was assessed using a multi-color pulse-amplitude-modulation chlorophyll fluorometer for phytoplankton samples collected in the spring at 19 locations across the English Channel. The functional absorption cross section of photosystem II, photosynthetic electron transport (PETλ) parameters and non-photochemical quenching were analyzed using an original approach with a sequence of three statistical analyses. Linear mixed-effects models using wavelength as a longitudinal variable were first applied to distinguish the fixed effect of the population from the random effect of individuals. Population and individual trends of wavelength-dependent PETλ parameters were consistent with photosynthesis and photoacclimation theories. The natural phytoplankton communities studied were in a photoprotective state for blue wavelengths (440 and 480 nm), but not for other wavelengths (green (540 nm), amber (590 nm) and light red (625 nm)). Population-detrended PETλ values were then used in multivariate analyses (partial triadic analysis and redundancy analysis) to study ecological implications of PETλ dynamics among water masses. Two wavelength ratios based on the microalgae saturation parameter Ek (in relative and absolute units), related to the hydrodynamic regime and underwater light climate, clearly confirmed the physiological state of microalgae. They also illustrate more accurately that natural phytoplankton communities can implement photoacclimation processes that are influenced by in situ light quality during the daylight cycle in temporarily and weakly stratified water. Ecological implications and consequences of PETλ are discussed in the context of turbulent coastal ecosystems.

International audience; Anticoagulant rodenticides (AR) resistance has been defined as "a major loss of efficacy due to the presence of a strain of rodent with a heritable and commensurately reduced sensitivity to the anticoagulant". The mechanism that supports this resistance has been identified as based on mutations in the Vkorc1 gene leading to severe resistance in rats and mice. This study evaluates the validity of this definition in the fossorial water vole and explores the possibility of a non-genetic diet-based resistance in a strict herbivorous rodent species. Genetic support was explored by sequencing the Vkorc1 gene and the diet-based resistance was explored by the dosing of vitamins K in liver of voles according to seasons. From a sample of 300 voles, only 2 coding mutations, G71R and S149I, were detected in the Vkorc1 gene in the heterozygous state with low allele frequencies (0.5-1%). These mutations did not modify the sensitivity to AR, suggesting an absence of genetic Vkorc1-based resistance in the water vole. On the contrary, vitamin K1 was shown to be 5 times more abundant in the liver of the water vole compared to rats. This liver concentration was shown to seasonally vary, with a trough in late winter and a peak in late spring/early summer related to the growth profile of grass. This increase in concentration might be responsible for the increased resistance of water voles to AR. This study highlights a non-genetic, diet-related resistance mechanism in rodents to AR. This diet-based resistance might explain the different evolution of the Vkorc1 gene in the fossorial water vole compared to rats and mice.

From 2000 to 2016, substantial changes in biomass and community structure of small pelagic fish and mesozooplankton have been reported in the Bay of Biscay. Since significant relationships have been found between phytoplankton chlorophyll a and mesozooplankton as well as between phytoplankton chlorophyll a and shifts in sardine body condition, it was hypothesized that phytoplankton communities may have also been affected during this period and may have played a role in these changes. However, the available data were insufficient to validate this hypothesis and the causes of these changes remained unexplained. The present study analyzed a spatio-temporal marine microphytoplankton dataset collected during the annual PELGAS (PELagiques GAScogne) surveys from 2003 to 2014. The thorough analysis of microphytoplankton taxonomic composition, with an approach integrating the relative role of environmental conditions as well as biotic interactions and applying the concept of ecological niche, confirmed that significant modifications in microphytoplankton community structure occurred during this period. Temporal changes were stronger than spatial differences at these sampling scales. Three main periods, 2003–2005, 2006 and 2007–2014, showing different community structure, diversity and dominant taxonomic units were highlighted. Twenty eight taxonomic units were involved in these community changes. Among them, five were identified as the protagonists (Pseudo-nitzschia spp., Gymnodinium spp. + Gyrodinium spp., Leptocylindrus danicus, Leptocylindrus minimus and Chaetoceros sp.). Variations in water temperature and equivalent freshwater depth constrained the realized ecological niches of these species and explained, at least in part, changes in community structure. This study stresses the need to improve our knowledge of phytoplankton species ecological niches and to take into account biotic interactions for a thorough understanding of the processes shaping plankton communities and the resulting diversity patterns.

Depth is one of the environmental variables influencing the structure of marine food webs by directly or indirectly influencing benthic-pelagic coupling and predator-prey relationships. In shallow waters, the high degree of connectivity between pelagic and benthic networks results in complex systems with multiple interactions. Digestive tract (DT) and stable isotope (SI) analyses were used to investigate depth-related changes in feeding patterns for 33 fish species (eastern English Channel [EEC]) collected between 5 m and 80 m depth. Fish species were first arranged into functional groups based upon trophic and habitat similarities. DTs were used to determine the general topology of the food web and SIs were used to estimate the contributions of different sources to fish diets. At the scale of the aggregated EEC food web, the main food sources for all groups were of benthic origin (> 50%). The aggregated food web was then used as a template to explore the influence of depth on resource use by predatory fish. Mixing models including depth as a continuous covariate successfully untangled and identified different feeding strategies among functional groups. In shallow waters, fish species benefited from both pelagic and benthic prey whereas, in deeper waters, they fed predominantly on either benthic or pelagic sources depending on their habitat preferences. Our results support the hypothesis of a stronger benthic-pelagic coupling in shallow waters, notably through fish diet, and highlight the importance of including environmental factors such as depth as proxies of habitat variation to fully understand resource use and food web structure in epicontinental seas.

International audience; Arenicola marina is a polychaete (Lophotrochozoan) displaying a complex bentho-pelagic life cycle with two larval dispersal phases, only partially described up to now. A Dynamic Energy Budget (DEB) model was applied to the species in order to reconstruct its life cycle and growth under in situ environmental conditions. Two types of DEB models are usually applied to other Lophotrochozoans displaying similar life cycles: the standard (std-) model, applied to polychaetes (5 entries among the 1524 of the Add-my-Pet database on the 18/10/2018), and the abj-model, which includes an acceleration of metabolism between birth and metamorphosis, and which has been applied to most molluscs (77 abj-entries out of the 80 mollusc entries) enabling better fit predictions for the early life stages. The parameter estimation was performed with both models to assess the suitability of an abj-model for A. marina. The zero-variate dataset consisted of length and age data at different life cycle stages, the lifespan, the maximum observed length, and the wet weight of an egg. The uni-variate dataset consisted of two growth experiments from the literature at two food levels and several temperatures, laboratory data of oxygen consumption at several temperatures, and fecundity for different lengths. The predictions of the abj-model fitted better to the data (SMSE = 0.29). The acceleration coefficient was ca 11, which is similar to mollusc values. The field growth curves and the scaled functional responses (as a proxy of food levels) were suitably reconstructed with the new parameter set. The reconstruction of the early life-stages chronology according to in situ environmental conditions of a temperate marine ecosystem indicated a first dispersal phase of 5 days followed by a 7 months temporary settlement before a second dispersal phase in spring, at the end of metamorphosis. We emphasize the need for using abj-models for polychaetes in future studies.

International audience; Vitamin K is crucial for many physiological processes such as coagulation, energy metabolism, and arterial calcification prevention due to its involvement in the activation of several vitamin K-dependent proteins. During this activation, vitamin K is converted into vitamin K epoxide, which must be re-reduced by the VKORC1 enzyme. Various VKORC1 mutations have been described in humans. While these mutations have been widely associated with anticoagulant resistance, their association with a modification of vitamin K status due to a modification of the enzyme efficiency has never been considered. Using animal models with different Vkorc1 mutations receiving a standard diet or a menadione-deficient diet, we investigated this association by measuring different markers of the vitamin K status. Each mutation dramatically affected vitamin K recycling efficiency. This decrease in recycling was associated with a significant alteration of the vitamin K status, even when animals were fed a menadione-enriched diet suggesting a loss of vitamin K from the cycle due to the presence of the Vkorc1 mutation. This change in vitamin K status resulted in clinical modifications in mutated rats only when animals receive a limited vitamin K intake totally consistent with the capacity of each strain to recycle vitamin K.

Vitamin K is crucial for many physiological processes such as coagulation, energy metabolism, and arterial calcification prevention due to its involvement in the activation of several vitamin K-dependent proteins. During this activation, vitamin K is converted into vitamin K epoxide, which must be re-reduced by the VKORC1 enzyme. Various VKORC1 mutations have been described in humans. While these mutations have been widely associated with anticoagulant resistance, their association with a modification of vitamin K status due to a modification of the enzyme efficiency has never been considered. Using animal models with different Vkorc1 mutations receiving a standard diet or a menadione-deficient diet, we investigated this association by measuring different markers of the vitamin K status. Each mutation dramatically affected vitamin K recycling efficiency. This decrease in recycling was associated with a significant alteration of the vitamin K status, even when animals were fed a menadione-enriched diet suggesting a loss of vitamin K from the cycle due to the presence of the Vkorc1 mutation. This change in vitamin K status resulted in clinical modifications in mutated rats only when animals receive a limited vitamin K intake totally consistent with the capacity of each strain to recycle vitamin K.

International audience; Few studies have reported quantitative data about the levels of prenylated coumarins in Ferula sp. Yet, the toxicity of Ferula sp. is only due to the presence of prenylated coumarins and to their concentrations and all studies suggest the existence of several chemotypes within the same species or even within the same variety. The aim of this study was to investigate the hypothesis of different chemotypes in french Ferula sp. in relationship with the botanical species. In this objective, the species of giant fennels and their concentrations in prenylated coumarins were explored. Three different species or subspecies of giant fennel were detected in continental France: F. communis communis communis L., F. communis catalaunica microcarpa Cauwet-Marc and F. glauca L. Surprisingly, the three species/subspecies of giant fennels were found to be located in exclusive and well separated geographical areas. In French giant fennels, ferulenol and ferprenin were detected. Distribution of ferulenol and ferprenin were found to be different between botanical varieties, but also according to the season, the soil and the altitude. Our study seems to suggest that among F. communis species, the same plant can be regarded as poisonous at one point and another as non-poisonous.

International audience

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [ADD1_IRSTEA]Dynamique et fonctionnement des écosystèmes; International audience; Trophic ecology is the study of feeding interactions and food acquisition by organisms. It includes the causes and consequences of those behaviours at all levels of biological organisation. As a field of research, it crosses many disciplinary boundaries and provides knowledge that is pertinent to many other areas of ecology. Here we list and categorise the methods available to trophic ecologists whose toolbox has broadened considerably in recent years. They encompass empirical and numerical approaches with focus ranging from molecules to ecosystems. We further examine the relationship of each method to features such as the scale of observation (from microbes to largest organisms) and organisational level (from individuals to ecosystems) as well as the ecological question the method is capable of answering (from detecting predator-prey relationships to studying implications and consequences at different scales). Our survey reveals a very wide range of methodologies, each more-or-less appropriate for a particular line of research. It also identifies deficits, for example, trophic interactions at microscopic scales, for which empirical methods have hardly been used, as well as trophic models that have failed to consider fluxes at the ecosystem scale. Furthermore, we note that the combination of methodologies remains under-exploited despite great opportunities to solve complex ecological questions and to foster the emergence of new insights and hypotheses regarding organism, population and/or ecosystem properties.

International audience; The black-lipped pearl oyster (Pinctada margaritifera) is extensively farmed in French Polynesia to produce black pearls. For a sustainable management of marine resources, studying interactions between organisms and environment, and the associated factors and processes that will impact their life cycle and thus modulate population dynamics is a major research priority. Here, we describe black-lipped pearl oyster energy acquisition and use, and its control by temperature and food concentration within the Dynamic Energy Budget (DEB) theory framework. The model parametrization was based on literature data and a specific laboratory experiment. Model validation was carried out thanks to historical in-situ datasets and a dedicated field survey. Three theoretical environmental scenarios were built to investigate the response of the pearl oyster to environmental variations. We successfully modeled a wide range of life-stage-specific traits and processes, especially the delayed acceleration of growth after settlement. Applying the model on field data collected at three different culture sites required only one free-fitted parameter, the half saturation coefficient Xk, which controls how ingestion depends on food density. Xk integrates all variations linked to the trophic environment. Analysis of the kinetics of energy fluxes under theoretical environmental scenarios suggests that temperature variations induce seasonality of reproduction in a species thought to spawn opportunistically throughout the whole year. The major influence of food concentration fluctuations on growth rate and reproductive effort is highlighted. The model showed the lower performances associated with recovery time between food-rich and starvation periods. The implications of these findings in the context of black pearl farming in a changing environment are discussed.

International audience