Capacité de surfusion des premiers stades de vie du ravageur Deroceras reticulatum

La température peut affecter significativement la survie, le développement, la croissance et la fécondité des organismes ectothermes. Les recherches portant sur la tolérance thermique et les réponses physiologiques adaptatives de la Limace grise Deroceras reticulatum, ravageur largement répandu en agriculture, produiront des informations importantes qui aideront à prédire le risque limace dans les cultures et ainsi minimiser les traitements molluscicides. Pour évaluer la variabilité de la capacité de surfusion chez cette espèce, la température de congélation (Tc) a été mesurée au cours du développement embryonnaire (embryons aux stades I, V et VI, et à l’éclosion) sur des œufs incubés à différentes températures (10°C, 15°C et 20°C), et comparée aux résultats obtenus chez les adultes. Aucune variation de la capacité de surfusion n’a été mise en évidence pendant le développement embryonnaire, mais elle varie de façon significative entre les différents stades, avec des Tc moyennes de -5,1°C chez les adultes et de -12,2°C chez les nouveau-nés, les œufs se positionnant entre ces deux stades avec une Tc moyenne de -10,7°C. Les œufs possèdent probablement un taux de survie supérieur à celui des adultes qui sont plus susceptibles de congeler. Les nouveau-nés seraient capables de survivre à de courtes périodes de températures négatives survenant en début de printemps. Contrairement aux adultes partiellement tolérants à la congélation, les œufs et les nouveau-nés pourraient être intolérants à la congélation. Pour valider notre hypothèse, des recherches supplémentaires porteront sur les adaptations biochimiques des différents stades du cycle de vie, et rechercheront en particulier les cryoprotecteurs et les protéines antigel pouvant s’accumuler dans les tissus lors de stress thermiques.Ambient environmental temperature can significantly affect survival, development, growth and fecundity of ectotherm species. Research on cold tolerance and adaptive physiological responses of the Grey field slug, Deroceras reticulatum, yields important information that can be used to aid in the prediction of crop infestation and damage, and thus provide a basis for minimizing pesticide treatments. To evaluate the supercooling capacity of the Grey field slug, the temperature of crystallization (Tc) was measured during the embryonic development of eggs (stage I, stage V, stage VI and hatchling) at three different incubation temperatures (10°C, 15°C and 20°C), and compared to results obtained from adults. No significant effect of incubation temperature on Tc was found, regardless of the developmental stage. Although no variation of supercooling ability was identified during embryogenesis, this did vary significantly among life stages, with Tc values of -5.1°C in adults and -12.2°C in hatchlings; a Tc value of -10.7°C was found for the egg stage. Eggs are likely to have a higher survival rate than adults which are more susceptible to freezing. Hatchlings are equipped to survive potential cold pulses that occur early in the spring. While adults may exhibit limited partial-freeze tolerance, eggs and hatchlings might be freeze avoidant. Additional research to support this hypothesis will be focused on biochemical adaptations within the various life stages, in particular by exploring cryoprotectants and antifreeze proteins that may accumulate in body tissues during thermal stress

Adaptations of a native Subantarctic flightless fly to dehydration stress: more plastic than we thought? ( Short Communication)

Water conservation is a critical aspect affecting the survival, distribution and abundance of terrestrial arthropods. In this study we investigate mechanisms of dehydration tolerance of the native, flightless fly, Calycopteryx moseleyi, inhabiting contrasting environments at two localities in the Kerguelen Islands. We compare the survival abilities and management of body water content of adult flies from two different ecophenotypes when exposed to conditions of low relative humidity. Our results suggest a broad plasticity in the responses of C. moseleyi to desiccation, showing distinct local adaptations to environmental conditions

Physiological responses of cold acclimation in Drosophila suzukii

editorial reviewedThe spotted wing drosophila (SWD) Drosophila suzukii is an invasive pest. To control this pest, information about its cold tolerance is required. Several studies have focused on SWD overwintering strategies and reported increased cold tolerance of winter morph (WM) compared to summer morph (SM). However, underlying mechanisms of this difference are not yet known. Our first goal was to study the impact of WM-inducing conditions on SWD cold tolerance and their metabolites composition. We expected to find an accumulation of cryoprotectant metabolites in cold hardy WM flies. Flies were reared at 25°C to induce SM, or at 10°C to induce WM. Cold tolerance was assayed by measuring survival after a stress at -5°C/1h40, minimal critical temperature and chill coma recovery. All metrics confirmed that WM-inducing conditions deeply promoted cold tolerance. SM and WM metabotypes were compared using target and quantitative GC/MS profiling. WM were characterized by an accumulation of several carbohydrates and amino acids, but quantitative changes were rather small (max 6 fold-change). Because robustness in metabolic networks is supposed to be a key element of cold tolerance, we assessed whether different levels of cold acclimation would favor metabolic stability. We generated four different phenotypes: development at 10°C to generate WM that were next acclimated as adults for 7 days at 10 or 25°C (WM10 or WM25) and development at 25°C to generate SM that were next acclimated as adults for 7 days at 10 or 25°C (SM10 or SM25). Using the same measures of cold tolerance, we found that cold tolerance ranked as follow: WM10>SM10>WM25>SM25. Stability of metabolic homeostasis was assessed in these four phenotypic groups using time-series GC/MS profiling. We monitored profiles before, right after, 4h, 8h or 12h after an acute cold shock. During recovery, both WM25 and SM25 metabotypes strongly deviated from origin, and did not return to initial state. This alteration was correlated with uncontrolled augmentation of the total amount of amino acids, which is symptomatic of cold injuries. WM10 presented the strongest temporal stability of metabolic profiles, suggesting a capacity to maintain homeostasis in this cold hardy phenotype. Finally, SM10 presented an intermediate response (as for cold tolerance). Data suggest that the proximal acclimation treatment (ie. at adult stage) is more critical in promoting cold tolerance that acclimation during development. Data corroborate that cold hardiness is associated to metabolic stability during stress and recovery. These results give new information to understand SWD cold tolerance

Cold Acclimation Favors Metabolic Stability in Drosophila suzukii

The invasive fruit fly pest, Drosophila suzukii, is a chill susceptible species, yet it is capable of overwintering in rather cold climates, such as North America and North Europe, probably thanks to a high cold tolerance plasticity. Little is known about the mechanisms underlying cold tolerance acquisition in D. suzukii. In this study, we compared the effect of different forms of cold acclimation (at juvenile or at adult stage) on subsequent cold tolerance. Combining developmental and adult cold acclimation resulted in a particularly high expression of cold tolerance. As found in other species, we expected that cold-acclimated flies would accumulate cryoprotectants and would be able to maintain metabolic homeostasis following cold stress. We used quantitative target GC-MS profiling to explore metabolic changes in four different phenotypes: control, cold acclimated during development or at adult stage or during both phases. We also performed a time-series GC-MS analysis to monitor metabolic homeostasis status during stress and recovery. The different thermal treatments resulted in highly distinct metabolic phenotypes. Flies submitted to both developmental and adult acclimation were characterized by accumulation of cryoprotectants (carbohydrates and amino acids), although concentrations changes remained of low magnitude. After cold shock, non-acclimated chill-susceptible phenotype displayed a symptomatic loss of metabolic homeostasis, correlated with erratic changes in the amino acids pool. On the other hand, the most cold-tolerant phenotype was able to maintain metabolic homeostasis after cold stress. These results indicate that cold tolerance acquisition of D. suzukii depends on physiological strategies similar to other drosophilids: moderate changes in cryoprotective substances and metabolic robustness. In addition, the results add to the body of evidence supporting that mechanisms underlying the different forms of acclimation are distinct

Langues vernaculaires et langue des mathématiques à la fin du Moyen Âge : l’exemple des arithmétiques commerciales du sud de la France

Charrier-Spiesser Maryvonne. Langues vernaculaires et langue des mathématiques à la fin du Moyen Âge : l’exemple des arithmétiques commerciales du sud de la France. In: Les langues du Sud : entre érosion et émergence. Actes du 126e Congrès national des sociétés historiques et scientifiques, « Terres et hommes du Sud », Toulouse, 2001. Paris : Editions du CTHS, 2004. pp. 105-120. (Actes du Congrès national des sociétés savantes, 126

New insights into population structure and length-mass relationships in Notodiscus hookeri, the single land snail native from sub-Antarctic islands

International audienc

Facteurs influençant la composition du régime alimentaire de l'escargot petit-gris Hélix aspersa Müller (gastéropode terrestre)

La composition du régime alimentaire de l'escargot petit-gris Helix aspersa en milieu naturel a été déterminée pour deux populations grâce à la reconnaissance des épidermes et des phytolithes végétaux dans les fèces. Les résultats de cette étude associés à celle des préférences alimentaires d'Helix aspersa au laboratoire et à l'analyse biochimique (RMN, CG-MS, ICP-MS) de certaines espèces végétales appétentes (Urtica dioica, Carduus tenuifloris, Picris echioides) ou inappétentes (Beta maritima, Elytrigia repens, Brachythecium rutabulum) ont permis de mettre en évidence l'influence des métabolites primaires et secondaires et des composants inorganiques des végétaux sur les choix alimentaires de cette espèce. Les informations chimiques fournies aux escargots par les plantes et leur surface foliaire associées à l'histoire alimentaire des animaux leur permettent d'effectuer une sélection optimale des éléments composant leur alimentation.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Le statut de la monnaie dans les arithmétiques marchandes de la fin du Moyen Âge : l’exemple de la France

The first purpose of the books of commercial arithmetics which were produced in France during the 15th Century is to train to mathematics devoted to commerce. In this purpose, money is an essential matter, and these treatises give us valuable information about currency and, through the exercises, about the merchant life and customs of that time. But the real subject being to teach practical mathematics, we intend to discuss in this paper what use of money is made by the authors, and how mathematical priorities can affect the reality of commercial exchanges.Les traités d’arithmétique commerciale qui ont fleuri en France dans le courant du XVe siècle ont pour but premier d’initier aux mathématiques utiles au commerce. Dans cette optique, la monnaie est tout naturellement un thème privilégié et ces textes nous livrent des renseignements précieux sur les devises en cours, leur circulation, et à travers les exercices, sur la vie et les pratiques commerciales de l’époque. Mais le sujet central n’étant pas la monnaie, nous nous proposons d’analyser ici quels types d’usage en font les auteurs, et dans quelle mesure les priorités mathématiques affectent la réalité des échanges commerciaux.Lamassé Stéphane, Charrier-Spiesser Maryvonne. Le statut de la monnaie dans les arithmétiques marchandes de la fin du Moyen Âge : l’exemple de la France. In: Revue numismatique, 6e série - Tome 167, année 2011 pp. 169-170

Etude inter-populationnelle de la tolerance au froid chez la limace grise Deroceras reticulatum

International audienc

L effet du régime alimentaire sur la reproduction et les processus physiologiques chez les escargots terrestres Cornu aspersum et Helix pomatia

Organisms often encounter environmental heterogeneity in space and time, and may adapt their life histories. In Cornu aspersum reproductive strategy depended on seasonal time constraints, and the investment in reproduction was influenced by the energy available in the environment. Nutrients deposited in eggs might enhance offspring survival. In Helix pomatia that is used recently in low input snail farms in Germany to maintain this endangered species as a regional specialty under the name Albschneck®, showed low reproductive success even with high energy food. Helix pomatia preserves ice nucleating bacteria and accumulates cryprotectants to enhance cold hardiness during hibernation. Mortality could be related to perpetual physiological adjustments to high environmental variations but also be due to limited resource allocation to survival maintaining processes.Les organismes rencontrent souvent de l hétérogénéité dans l espace et dans le temps et devront adapter leur traits d histoire de vie. Chez Cornu aspersum, la stratégie de reproduction dépend des contraintes saisonnières, et l investissement dans la reproduction est influencé par l énergie disponible dans l environnement. Des nutriments déposés dans les oeufs pourraient augmenter la probabilité de survie des juvéniles. Chez Helix pomatia, qui est utilisé dans des élevages biologiques afin de maintenir cette espèce menacée comme spécialité régionale sous le nom Albschneck®, le succès reproducteur est faible même avec une alimentation riche en énergie. Helix pomatia préserve des bactéries nucléantes dans l intestin et accumule des cryoprotecteurs pour améliorer la résistance au froid pendant l hiver. La mortalité pourrait être liée à un ajustement perpétuel des processus physiologiques aux importantes variations environnementales ainsi qu à une allocation limitée vers des processus de survie.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF