Are Amphipod invaders a threat to the regional biodiversity? Conservation prospects for the Loire River

The impact of invasions on local biodiversity is well established, but their impact on regional biodiversity has so far been only sketchily documented. To address this question, we studied the impact at various observation scales (ranging from the microhabitat to the whole catchment) of successive arrivals of non-native amphipods on the amphipod assemblage of the Loire River basin in France. Amphipod assemblages were studied at 225 sites covering the whole Loire catchment. Non-native species were dominant at all sites in the main channel of the Loire River, but native species were still present at most of the sites. We found that the invaders have failed to colonize most of tributaries of the Loire River. At the regional scale, we found that since the invaders first arrived 25 years ago, the global amphipod diversity has increased by 33% (from 8 to 12 species) due to the arrival of non-native species. We discuss the possibility that the lack of any loss of biodiversity may be directly linked to the presence of refuges at the microhabitat scale in the Loire channel and in the tributaries, which invasive species have been unable to colonize. The restoration of river quality could increase the number of refuges for native species, thus reducing the impact of invader

Répartition des Gammaridae épigés (Crustacés, Amphipodes) dans la Loire et les rivières de la Région Centre (France)

Ce travail présente la répartition de 5 espèces de Gammaridae (Echinogammarus berilloni, E. spinulicornis, Gammarus fossarum, G. p. pulex, G. roeseli) dans la Région Centre qui correspond approximativement au bassin de la Loire moyenne et au sud du bassin de la Seine moyenne. Environ 300 stations ont été échantillonnées entre 1980 et 1990. G. fossarum n'est présente que dans l'Allier. L'espèce la plus répandue est G. p. pulex ; elle apparaît souvent en sympatrie avec E. berilloni. E. spinulicornis et G. roeseli sont deux espèces en extension dans la région. E. spinulicornis est nettement dominante à l'ouest, mais uniquement dans le bassin de la Loire, tandis que G. roeseli est plus abondante à l'est aussi bien dans le bassin de la Loire que dans celui de la Seine

Description, répartition et cycle biologique de la larve d'Hydropsyche bulgaromanorum Malicky 1977 (Trichoptera, Hydropsychidae) dans la Basse Loire

La larve d'Hydropsyche bulgaromanorum est décrite par comparaison avec celles d'H. contubernalis et H. ornatula, avec lesquelles elle a souvent été confondue. H. bulgaromanorum, considérée comme une espèce plutôt médioeuropéenne et, jusqu'à présent, inconnue en France, apparaît dans la Loire dès la confluence du Cher puis devient l'espèce d'Hydropsychidae dominante de la Basse Loire. H. bulgaromanorum caractériserait le métapotamal. Son cycle biologique est bivoltin

Machine learning control for experimental shear flows targeting the reduction of a recirculation bubble

International audienceThe goal is to experimentally reduce the recirculation zone of a turbulent flow(Re H = 31500). The flow is manipulated by a row of micro-blowers (pulsed jets) that areable to generate unsteady jets proportional to any variable DC. Already, periodic jet injectionat a forcing frequency of St H = 0.226 can effectively reduce the reattachment length andthus the recirculation zone. A model-free machine learning control (MLC) is used to improveperformance. MLC optimizes a control law with respect to a cost function and applies geneticprogramming as regression technique. The cost function is based on the recirculation lengthand penalizes actuation. MLC is shown to outperform periodic forcing. The current studydemonstrates the efficacy of MLC to reduce the recirculation zone in a turbulent flow regime.Given current and past successes, we anticipate numerous experimental MLC applications

Rapid range extension of the Ponto-Caspian amphipod <I>Dikerogammarus villosus</I> in France: potential consequences

International audienc

Antidiarrhoeal properties of a novel sigma ligand (JO 2871) on toxigenic diarrhoea in mice: mechanisms of action

Background and aims: Sigma ligands display antisecretory activity against various secretagogues, suggesting antidiarrhoeal properties. In this study, we evaluated: (i) the antidiarrhoeal effect of JO 2871, a high affinity sigma ligand, in three models of toxigenic diarrhoea in mice; and (ii) the site and mechanism of action of this compound. Methods: Faeces were collected after toxin or vehicle administration in male DBA2 or NMRI mice. Diarrhoea was determined by cumulative stool weight (mg) over a 120 minute period. Diarrhoea was induced by intravenous administration of Salmonella enteriditis lipopolysaccharide (LPS), or oral administration of Escherichia coli heat stable (E coli-sta) or Clostridium difficile toxins. Two sigma ligands, igmesine and JO 2871, were administered either orally or intravenously, 60 and 30 minutes before the toxins, respectively. JO 2871 was also given orally 30 minutes after E coli-sta. In addition, JO 2871 was administered intracerebroventricularly five minutes before LPS and E coli-sta. BMY 14802 (1000 μg/kg orally), a sigma receptor antagonist, or cyclosomatostatin (CSS 1 μg/kg intravenously), a somatostatin antagonist, were given five minutes prior to JO 2871 in LPS, E coli-sta, and C difficile toxin treated mice. Gastric emptying and intestinal transit were evaluated after oral JO 2871 and BMY 14802 and intravenous CSS. Results: Stool weight measured 120 minutes after administration of the toxins was significantly increased. Oral JO 2871 and igmesine dose dependently inhibited toxigenic diarrhoea in all models. ED(50) values obtained using JO 2871 (1–20 μg/kg) were more than 40 times lower than those obtained with igmesine. Oral JO 2871 given after E coli-sta also inhibited diarrhoea in a dose dependent manner (ED(50) 50 μg/kg). Both sigma ligands were active by the intravenous route on LPS and E coli-sta induced stool weight increases. JO 2871 administered intracerebroventricularly failed to block this effect at any dose tested. Both BMY 14802 and CSS reversed the antidiarrhoeal effect of oral JO 2871. JO 2871, BMY 14802, and CSS did not affect transit parameters. Conclusions: JO 2871 exerts a potent oral antidiarrhoeal effect, acting peripherally through sigma sites and somatostatin release