DYRK1A, a Novel Determinant of the Methionine-Homocysteine Cycle in Different Mouse Models Overexpressing this Down-Syndrome-Associated Kinase

BACKGROUND:Hyperhomocysteinemia, characterized by increased plasma homocysteine level, is associated with an increased risk of atherosclerosis. On the contrary, patients with Down syndrome appear to be protected from the development of atherosclerosis. We previously found a deleterious effect of hyperhomocysteinemia on expression of DYRK1A, a Down-syndrome-associated kinase. As increased expression of DYRK1A and low plasma homocysteine level have been associated with Down syndrome, we aimed to analyze the effect of its over-expression on homocysteine metabolism in mice. METHODOLOGY/PRINCIPAL FINDINGS:Effects of DYRK1A over-expression were examined by biochemical analysis of methionine metabolites, real-time quantitative reverse-transcription polymerase chain reaction, and enzyme activities. We found that over-expression of Dyrk1a increased the hepatic NAD(P)H:quinone oxidoreductase and S-adenosylhomocysteine hydrolase activities, concomitant with decreased level of plasma homocysteine in three mice models overexpressing Dyrk1a. Moreover, these effects were abolished by treatment with harmine, the most potent and specific inhibitor of Dyrk1a. The increased NAD(P)H:quinone oxidoreductase and S-adenosylhomocysteine hydrolase activities were also found in lymphoblastoid cell lines from patients with Down syndrome. CONCLUSIONS/SIGNIFICANCE:Our results might give clues to understand the protective effect of Down syndrome against vascular defect through a decrease of homocysteine level by DYRK1A over-expression. They reveal a link between the Dyrk1a signaling pathway and the homocysteine cycle

Écologie trophique de deux espèces sympatriques de phoques en périphérie de leur aire de répartition

Harbour seal (Phoca vitulina) and grey seal (Halichoerus grypus) are two sympatric marine mammal species that are increasingly considered as potential competitors, especially at their European core distributions. The objective of this PhD was to study the foraging strategies and trophic ecology of these species at the limit of their range (Baie de Somme, Eastern English Channel, France), and to investigate the hypothesis of potential interspecific competition. Biotelemetry devices were fitted on 49 individuals to document their movements and dives at sea.The analysis of surface locations and diving behaviour, completed recently by the detection of Prey Capture Attempts (accelerometry), allowed for a better understanding of the two seal species’ foraging strategies and improved the detection of their foraging areas. Trophic niches of the two seal species were then characterised with the analysis of diet, stable isotopes (in the whiskers of the same captured individuals), and foraging areas. A high interspecific trophic overlap was identified between these niches, resulting from the consumption of benthic flatfish in coastal areas, and we suggest that it provides here the basis for potential competition between both species. This study also showed the key role of individual foraging strategies on the ecological conclusions at the scale of the species/sub-population, including that the potential competition may be due to some individual grey seal strategies. Continuing these studies is essential to detect any potential ecological changes that could be trophically-induced.Le phoque veau-marin (Phoca vitulina) et le phoque gris (Halichoerus grypus), deux espèces sympatriques de mammifères marins, sont de plus en plus considérés comme des compétiteurs potentiels, et ce plus particulièrement au cœur de leur distribution européenne. L’objectif de cette thèse est d’étudier les stratégies de chasse et l’écologie trophique de ces espèces en limite de leur aire de distribution (baie de Somme, Manche Est, France), et d’explorer l’hypothèse de compétition interspécifique. Des outils de bio-télémétrie ont été déployés sur 49 individus afin d’obtenir des données sur leurs déplacements et plongées en mer. L’analyse des localisations en surface et du comportement en plongée, complétée plus récemment par la détection de tentatives de captures de proies (accélérométrie), a permis de mieux comprendre les stratégies de chasse de ces espèces, et d’améliorer la détection des zones de chasse. Les niches trophiques des deux espèces de phoques ont ensuite été caractérisées par analyse du régime alimentaire, des isotopes stables (vibrisses des mêmes individus capturés), et des zones de chasse. Un important chevauchement interspécifique a été identifié entre ces niches, résultant de la consommation de poissons plats benthiques en zone côtière, ce qui apporte ici le contexte informatif d’une potentielle compétition. Cette étude montre aussi le rôle clé des stratégies individuelles de chasse sur les conclusions écologiques à l’échelle de l’espèce/sous-population,dont la potentielle compétition qui serait induite par certains phoques gris. La poursuite des suivis est nécessaire pour détecter tout potentiel changement écologique dont l’origine serait trophique

Trophic ecology of two sympatric seal species at the limit of their distribution range

Le phoque veau-marin (Phoca vitulina) et le phoque gris (Halichoerus grypus), deux espèces sympatriques de mammifères marins, sont de plus en plus considérés comme des compétiteurs potentiels, et ce plus particulièrement au cœur de leur distribution européenne. L’objectif de cette thèse est d’étudier les stratégies de chasse et l’écologie trophique de ces espèces en limite de leur aire de distribution (baie de Somme, Manche Est, France), et d’explorer l’hypothèse de compétition interspécifique. Des outils de bio-télémétrie ont été déployés sur 49 individus afin d’obtenir des données sur leurs déplacements et plongées en mer. L’analyse des localisations en surface et du comportement en plongée, complétée plus récemment par la détection de tentatives de captures de proies (accélérométrie), a permis de mieux comprendre les stratégies de chasse de ces espèces, et d’améliorer la détection des zones de chasse. Les niches trophiques des deux espèces de phoques ont ensuite été caractérisées par analyse du régime alimentaire, des isotopes stables (vibrisses des mêmes individus capturés), et des zones de chasse. Un important chevauchement interspécifique a été identifié entre ces niches, résultant de la consommation de poissons plats benthiques en zone côtière, ce qui apporte ici le contexte informatif d’une potentielle compétition. Cette étude montre aussi le rôle clé des stratégies individuelles de chasse sur les conclusions écologiques à l’échelle de l’espèce/sous-population,dont la potentielle compétition qui serait induite par certains phoques gris. La poursuite des suivis est nécessaire pour détecter tout potentiel changement écologique dont l’origine serait trophique.Harbour seal (Phoca vitulina) and grey seal (Halichoerus grypus) are two sympatric marine mammal species that are increasingly considered as potential competitors, especially at their European core distributions. The objective of this PhD was to study the foraging strategies and trophic ecology of these species at the limit of their range (Baie de Somme, Eastern English Channel, France), and to investigate the hypothesis of potential interspecific competition. Biotelemetry devices were fitted on 49 individuals to document their movements and dives at sea.The analysis of surface locations and diving behaviour, completed recently by the detection of Prey Capture Attempts (accelerometry), allowed for a better understanding of the two seal species’ foraging strategies and improved the detection of their foraging areas. Trophic niches of the two seal species were then characterised with the analysis of diet, stable isotopes (in the whiskers of the same captured individuals), and foraging areas. A high interspecific trophic overlap was identified between these niches, resulting from the consumption of benthic flatfish in coastal areas, and we suggest that it provides here the basis for potential competition between both species. This study also showed the key role of individual foraging strategies on the ecological conclusions at the scale of the species/sub-population, including that the potential competition may be due to some individual grey seal strategies. Continuing these studies is essential to detect any potential ecological changes that could be trophically-induced

Comparing the horizontal and vertical approaches used to identify foraging areas of two diving marine predators

International audienceAccurately locating the foraging areas of diving marine predators is central to understanding their ecology and implementingconservation and management regulations. This study compares horizontal and vertical approaches of identifying seal foragingareas. We analysed GPS locations and dive data obtained from GPS/GSM tags fitted on eight grey seals (Halichoerusgrypus) and nine harbour seals (Phoca vitulina). In the horizontal dimension, we used the First Passage Time to identifyArea-Restricted Search (ARS) behaviour. In the vertical dimension, we used two dive criteria indicating benthic foragingbehaviour: dive shape and vertical descent speed. The two approaches were spatially compared using the Index of Differencesin Spatial Pattern. We found that the two approaches highlight similar hotspots when pooling all individuals of thesame species. However, the degree of overlap varied considerably at the individual level. Some individuals performed mostof their likely foraging dives (vertical dimension) in areas where they also displayed ARS behaviour (horizontal dimension),while others performed these dives both in and outside ARS zones. We suggest that comparing foraging areas detected fromhorizontal and vertical approaches (1) can strengthen the confidence in the efficiency of approaches to accurately spatializethe actual foraging effort of a diving predator at the scale of a colony (sampled with several individuals); and (2) providesmore comprehensive insights into potential interindividual differences in foraging strategies as some divergent individualstrategies may not be detected using only horizontal movements

Écologie trophique des phoques veaux-marins et des phoques gris en Manche Nord-Est : connaissances actuelles, résultats thèse et perspectives d’études.

International audienc

Trophic niche overlap between sympatric harbour seals(Phoca vitulina) and grey seals (Halichoerus grypus) at thesouthern limit of their European range (Eastern EnglishChannel)

International audienceSympatric harbour (Phoca vitulina) and grey seals (Halichoerus grypus) are increasinglyconsidered potential competitors, especially since recent local declines in harbourseal numbers while grey seal numbers remained stable or increased at their Europeancore distributions. A better understanding of the interactions between these speciesis critical for conservation efforts. This study aimed to identify the trophic nicheoverlap between harbour and grey seals at the southern limit of their Europeanrange, in the Baie de Somme (BDS, Eastern English Channel, France), where numbersof resident harbour seals and visiting grey seals are increasing exponentially. Dietaryoverlap was identified from scat contents using hierarchical clustering. Isotopic nicheoverlap was quantified using δ13C and δ15N isotopic values from whiskers of 18 individuals,by estimating isotopic standard ellipses with a novel hierarchical modeldeveloped in a Bayesian framework to consider both intraindividual variability andinterindividual variability. Foraging areas of these individuals were identified fromtelemetry data. The three independent approaches provided converging results, revealinga high trophic niche overlap due to consumption of benthic flatfish. Two dietclusters were dominated by either small or large benthic flatfish; these comprised85.5% [CI95%: 80.3%–90.2%]of harbour seal scats and 46.8% [35.1%–58.4%]of greyseal scats. The narrower isotopic niche of harbour seals was nested within that ofgrey seals (58.2% [22.7%–100%]overlap). Grey seals with isotopic values similar toharbour seals foraged in coastal waters close to the BDS alike harbour seals did, suggestingthe niche overlap may be due to individual grey seal strategies. Our findingstherefore provide the basis for potential competition between both species (foragingon benthic flatfish close to the BDS). We suggest that a continued increase in sealnumbers and/or a decrease in flatfish supply in this area could cause/amplify competitiveinteractions and have deleterious effects on harbour seal colonies

Des phoques suivis par balises en Manche - mer du Nord

International audienceEn 2019, des phoques gris et veaux-marins ont été équipés de balises au sein du Parc naturel marin des estuaires picards et de la mer d’Opale, afin de suivre leurs déplacements en mer et d’identifier leurs zones d’alimentation. Si les résultats de ce suivi montrent que la gestion de ces espèces protégées nécessite de prendre en compte une large échelle géographique, ils mettent également en évidence des enjeux interspécifiques forts au sein du parc

Fine scale foraging habitat selection by two diving central place foragers in the Northeast Atlantic

International audience1. Understanding the animal-habitat relationship at local scale is crucial in ecology, particularly to develop strategies for wildlife management and conservation. As this relationship is governed by environmental features and intra and inter-specific interactions, habitat selection of a population may vary locally between its core and edges. 2. This is particularly true for central place foragers, such as grey and harbour seals, whose trends in numbers vary among different regions in the Northeast Atlantic. Here, we aimed at studying how foraging habitat selection may vary locally with the influence of population trends and physical habitat features 3. Using GPS/GSM tags deployed in grey and harbour seal colonies of contrasting sizes, we investigate spatial patterns and foraging habitat selection by comparing trip characteristics and home range similarities, and fitting GAMM to the seal distribution and environmental data respectively. 4. We show that grey seal foraging habitat selection and spatial patterns differed markedly between regions. Grey seals may select environmental characteristics for their foraging habitat accounting for local differences in prey consumed. Spatial patterns were different might depend on local seal density and regional productivity, located from inshore to offshore areas for the limit ranges and core population respectively. Our results on foraging habitat selection reflected the coastal and sedentary behaviour of harbour seals. We found no difference in spatial patterns between colonies, except for the Inner Hebrides where seals foraged further, potentially reflecting density dependence pressure, as the number in this colony is higher. 5. These results suggest that local conditions might have a strong influence on population spatial ecology, highlighting as well the relevance of studying foraging habitat selection based on foraging behaviour at fine geographical scale, particularly if species are managed within regional units

DataSheet_1_Isotopic niches reveal the trophic structure of the cetacean community in the oceanic waters around the Azores.pdf

IntroductionThe oceanic waters around the Azores host a high diversity of cetaceans, with 28 species of toothed and baleen whales present year-round or seasonally. This high cetacean biodiversity likely plays an important role in the structure, functioning and productivity of the ecosystem, and may increase trophic redundancy, thus contributing to food web resilience to disturbances.MethodsHere we used stable isotope (δ13C and δ15N) analysis to characterize trophic niches, assess niche overlap, describe the trophic structure and discuss potential redundancy in the cetacean community. Using 407 samples from 12 species, we estimated Standard Ellipse Areas and overlaps between species and used a hierarchical clustering analysis to identify trophic guilds.Results and discussionδ13C and δ15N values ranged from -20.53 to -15.46‰ and from 7.78 to 14.41‰ respectively, suggesting the use of diverse habitats and resources among cetacean species. Clustering analysis revealed that species were grouped into four trophic guilds, segregated mainly by trophic position (TP): a low-TP guild with three zooplanktivore baleen whales, a mid-TP guild with micronektivores, a high-TP guild with micronekton and nekton consumers, and a cluster with only Pseudorca crassidens. There was significant isotopic niche overlap between one pair of species within each guild, indicating some potential for trophic redundancy in the community. Yet, these pairs also showed some form of spatial or temporal partitioning, suggesting that mechanisms promoting species coexistence could play a key role in structuring the cetacean community in the region and in its ecological role.</p