Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Climatic changes result in an increased in mean temperature and in a higher incidence of extreme weather events such as heat and cold waves. For ectotherms, such as insect parasitoids, the ability to remain active under extreme climatic conditions is a significant key to fitness. The body size of individuals, and in particular their surface to volume ratio, may play a role in their resistance to thermal conditions. The thermal tolerances are investigated of two closely-related sympatric parasitoid species [Aphidius avenae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiinae)] that have a similar ecology but differ in body size and phenologies. The critical thermal limits of individuals are assessed in both sexes of each parasitoid species and the influence of surface-volume ratios on their thermal tolerances. Aphidius avenae is less resistant to low temperatures and more resistant to high temperatures than A. rhopalosiphi. The lower surface to volume ratio of A. avenae individuals may help them to remain active in summer when experiencing heat waves. However, body size is not the sole factor that plays a role in differences of thermal tolerance between species and body size may not be an adaptation to extreme temperatures but rather a by-product of developmental regulation. Closely related sympatric species from the same ecological guild can have different thermal tolerances that may allow them to occur within the same habitat. The present study also highlights the importance of clearly defining how to measure critical thermal limits to determine the thermal tolerance of a species.
ISSN: 0307-6962

hal-00589094
https://hal.archives-ouvertes.fr/hal-00589094
DOI : 10.1111/j.1365-3032.2010.00758.x

Éditeur(s) : HAL CCSD BioMed Central
Résumé : Le régime de reproduction de Dicorynia guianensis (caesalpiniaceae), arbre de la forêt guyanaise a été étudié à l'aide des marqueurs enzymatiques. Le matériel végétal a été collecté en 1993 et 1995, sur le dispositif sylvicole de Paracou. Le taux d'allofécondation moyen de la population est élevé, tm = 0,85, stable d'une année à l'autre malgré une variation importante du taux de floraison. Le taux individuel varie entre les arbres mais aucune corrélation n'a pu être établie avec des facteurs spatiaux, densité de floraison ou distance aux plus proches voisins. L'hétérogénéité des nuages polliniques est sensible au niveau des agrégats et des arbres individuels, échelle spatiale où se déploie l'activité des insectes pollinisateurs. Nous n'avons en évidence aucune corrélation spatiale entre compositions des nuages polliniques individuels. Des distances de migration du pollen de 190 mètres ont été mise en évidence grâce aux allèles rares. Aucune différence significative du régime de reproduction de D. guianensis n'a été trouvée entre parcelles traitées et parcelles témoin du dispositif.
ISSN: 0999-193X

hal-01032370
https://hal.archives-ouvertes.fr/hal-01032370

Éditeur(s) : HAL CCSD
Résumé : International audience
To study the associations between occupation, industry and prostate cancer risk in Guadeloupe, a high incidence area. Incident cases of prostate cancer (707 cases) and 722 population controls were included. Information on lifetime occupational history and other potential risk factors was collected by interview. Logistic regression was used to estimate adjusted odds-ratios (OR) and their 95% confidence intervals (CI). A significantly decreased risk was observed in farmers (OR=0.5; CI 0.4-0.7), whereas marginally elevated ORs were found for farm workers, especially in sugarcane and banana farming. Banana plantation workers had been exposed to chlordecone, an estrogenic insecticide previously found to be associated with prostate cancer risk in this population. Significantly increased risks of prostate cancer were found in stock clerks (OR=2.7; CI 1.0-7.2), fishermen (OR=2.0; CI 1.0-4.0), mail distribution clerks (OR=7.7; CI 1.7-34.4) and electricians employed for more than 20 years (OR=4.0; CI 1.0-15.8), as well as in public administration (OR=1.8; CI 1.2-2.9), retail trade (OR=2.6; CI 1.1-6.0) and manufacture of food products (OR=2.0; CI 1.1-3.9), particularly sugar (OR=13.2; IC 1.6-108). Non-significantly elevated ORs were also seen for construction workers and transport equipment operators. Although the overall findings suggest that occupational factors have only a limited role in prostate cancer aetiology, elevated risks of prostate cancer were found in several occupations or industries. Exposure to pesticides, solvents, traffic-related air pollution, low physical activity, whole-body vibration may explain some of these increased risks.
Challenges for Occupational Epidemiology in the 21st Century EPICOH 2014
Chicago, United States

hal-01118558
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118558
DOI : 10.1136/oemed-2014-102362.312
PUBMED : 25018167

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth.
PLoS ONE

hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399/document
DOI : 10.1371/journal.pone.0020538
OATAO : 10156

Résumé : Les venins sont des armes sophistiquées, utilisées par les organismes venimeux pour se défendre des prédateurs, ainsi que pour paralyser et tuer leurs proies. Mais dans la nature, le bien n’est jamais très loin du mal, les toxines venimeuses pouvant se révéler être des agents thérapeutiques efficaces. Les peptides de venins de fourmis ont donc été étudiés dans cette thèse afin de déterminer le potentiel de ces toxines pour la découverte de molécules thérapeutiques innovantes. A l’instar des autres venins d’insectes, les venins de fourmis restent peu étudiés, principalement en raison de la petite taille de ces insectes et des quantités limitées de venins disponibles. Cependant, les fourmis offrent l’avantage d’être des insectes sociaux très abondants dans tous les milieux terrestres. En collectant les venins de plusieurs individus, il est donc possible d’obtenir des quantités suffisantes de venin pour les analyses biochimiques et pharmacologiques.Afin d’assurer la reproductibilité des analyses, une identification taxonomique correcte est nécessaire. Dans cette optique, un outil de chimiotaxonomie a été développé durant cette thèse (permettant ainsi de regrouper les venins provenant de plusieurs colonies afin de compenser les faibles quantités de matériel biologique par individu ou par colonie).Ensuite, nous nous sommes intéressés aux facteurs écologiques impliqués dans la diversification des venins de fourmis. Pour cela, la toxicité et la composition des venins de fourmis ont été analysés en relation avec le polyéthisme, la spécialisation alimentaire et la spécialisation défensive.La diversité écologique des fourmis a amplement contribuée à la diversification des venins. En étudiant les venins de 82 espèces de fourmis, nous avons révélé la grande diversité structurale des toxines. Bien que la majorité des peptidomes sont composés par de petits peptides linéaires, des peptides structurés par des ponts disulfure ont été révélés dans de nombreux venins et constituent de nouvelles familles structurales de toxines.La purification de certains de ces peptides à ponts disulfure a permis leur caractérisation biochimique et l’évaluation de leur rôle biologique. Ainsi nous avons décrit un groupe de peptides neurotoxiques, baptisés les formicitoxines qui sont capables de bloquer les canaux calcium humains de type L. La commutatoxine est, quant à elle, un peptide avec un pont disulfure qui semble activer les récepteurs humains TRPV1 et TRPV3 et laisse supposer une implication dans l’induction de la douleur chez les mammifères.La grande diversité des peptides mise en évidence dans les venins, associée à la grande diversité écologique et taxonomique des fourmis, suggère que les venins de fourmis constituent un nouveau champ d’exploration prometteur pour la recherche de molécules thérapeutiques et insecticides. Les venins de fourmis s’ajoutent à la chimiothèque conséquente déjà représentée par les venins des autres animaux venimeux.
Venoms are sophisticated weapons employed by venomous organisms to ward off predators, as well as to subdue and kill prey. However, in nature, good is never far from bad and venom toxins may prove to be efficient therapeutic agents. Ant venom peptides were investigated in the course of this thesis to evaluate their potential in the discovery of novel drugs. Like other insect venoms, ant venoms remain understudied, mainly due to the small size of individual ants and, so, the limited a mount of venom available. The ecological diversity of ants has largely contributed to venom diversification. By studying the venom peptidomes from 82 ant species, we have revealed the great structural diversity of the toxins. Although the majority of the peptidomes are comprised of small and linear peptides, peptides structured by disulfide bonds were also brought to light in numerous venoms and constitute novel structural classes of toxins. The purification of some of these disulfided peptides permitted their biochemical characterization and the assessment oft heir biological functions. The enormous peptide diversity revealed among venoms combined with the great ecological and taxonomical diversity of ants suggests that ant venoms constitute a promising new source in the search for both novel drugs and insecticides. Ant venom augments the vast bioactive molecules library represented by venoms from other venomous animals.

http://www.theses.fr/2015AGUY0829/document

Éditeur(s) : HAL CCSD
Résumé :  
Les Aracées forment une famille de plantes dont on connaît actuellement quelque 150 genres et 3300 espèces réparties sur toute la surface du globe, principalement dans les zones tropicales et équatoriales de l'Asie et de l'Amérique du Sud. Au-delà d'une immense diversité de formes, de modes de vies et d'habitats, les Aracées ont en commun - à quelques exceptions près - d'être entomophiles. Pour attirer et retenir les insectes qui les pollinisent, elles ont développé des inflorescences très particulières.
Insectes

hal-01032101
https://hal.archives-ouvertes.fr/hal-01032101

Résumé : Les attines sont des fourmis champignonnistes dans la zone allant des Etats-Unis à l'Argentine en passant par la Caraïbe. Les dégâts causés par ces ravageurs sont considérables et estimés à plusieurs millions de dollars par an. Elles sont de ce fait considérées comme l'un des premiers fléaux de l'agriculture de la zone (Cameron & Riggs, 1985 ; Fowler et al., 1986). En Guadeloupe, la "fourmi manioc" (Acromyrmexoctospinosus Reich) cause de nombreux dommages, aussi bien pour l'agriculture que dans les milieux naturels. Les dégâts occasionnés par ces fourmis ont nécessité l'utilisation de pesticides de synthèse. pour tenter de les combattre. La dangerosité de ces substances pour les milieux naturels et anthropisés ainsi que pour la santé publique est un contexte favorable à l'exploration de nouvelles pistes telles que l'utilisation de plantes à usages phytosanitaires. L'objet principal de cette thèse consiste à savoir si on peut déceler à partir de l'ethnopharmacologieTRAMIL des usages permettant de combattre cette fourmi et son symbiote fongique, Leucocoprinuss 'gongylophorus (Heim) MoeIler. Les protocoles retenus et présentés dans ce travail permettent d'observer les effets des usages de plantes choisis sur la survie et le comportement des insects et sur la croissance du symbiote. Ils ont été sélectionnés pour leur potentialité à mettre en évidence les différents types d'effets des extraits végétaux (insecticide par contact, insectifuge, toxique par ingestion, fongistatique ou fongicide). Six usages traditionnels issus de cinq plantes sont testés sur la fourmi: Mammea americana L., Nerium oleander L., Nicotiana tabacum L., Rollinia mucosa (Jacq.) Baill. et Trichilia pallida Sw. Cinq autres usages traditionnels sont testés sur le champignon : Allium cepa L., Allium sativum L., Lycopersicom esculentum Mill., Manihot esculenta Crantz et Senna alata (L.) Roxb. Les resultants obtenus permettent de dégager quelques pistes de lutte intéressantes contre ce ravageur.
Leaf-cutting ants are fungus-growing ants.Their geographie distribution ranges from southern United States to northern Argentina, incIuding the West Indies, Economic losses due to these ants were estimated at several million dollars per year. The latter statement makes they are considered as one of the most important pest species of the agricultural productions (Cameron & Riggs, 1985 ; Fowler et al., 1986). In (Guadeloupe, the most important invasive pest species which caused important losses in forests, gardens and field crops is 'cassava ant' (Acromyrmex octospinosus Reich). These huge losses required to use, synthetic chemical pesticides to control these leaf-cutting ants, the consequence of which is, irreversible' injuries on environment and on human health. As a matter of fact, this situation has prompted an increasing interest in alternative methods for pest control like plants with pesticide used. The main objective of this thesis is to know if traditional ethnopharmacological TRAMIL uses could help to fight against this ant and against the symbiotic fungus, Leucocoprinus gongylophorus (Heim) . Moeller. Methods used and presented in this work aIIowed to observe effects of selected plant uses on mortality and insect's behavior. The protocols performed were selected for their potentiality to detect the different types of insecticidal effects (contact toxicity, repellent effect, toxicity by ingestion, fungicidal or fungistatic). Six traditional plant uses of five plants were tested on the ant : Mammea americana L., Nerium oleander L., Nicotiana tabacum L.,Rollinia mucosa (Jacq) Baill. and Trichilia pallida Sw.Five other plants uses were tested on the fungus:Allium cepa L.,Lycopersicon esculentum Mill.,Manihot esculenta Crantz and Senna alata (L.) Roxb.The obtained résults provide us with some interesting trails to fight against this pest.

http://www.theses.fr/2011AGUY0469/document

Éditeur(s) : HAL CCSD Frontiers Media
Résumé : "Candidatus Liberibacter solanacearum" (Lso) has emerged as a serious threat world-wide. Five Lso haplotypes have been identified so far. Haplotypes A and B are present in the Americas and/or New Zealand, where they are vectored to solanaceous plants by the potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae). The fastidious nature of these pathogens has hindered the study of the interactions with their eukaryotic hosts (vector and plant). To understand the strategies used by these pathogens to infect their vector, the effects of each Lso haplotype (A or B) on psyllid fitness was investigated, and genome-wide transcriptomic and RT-qPCR analyses were performed to evaluate Lso gene expression in association with its vector. Results showed that psyllids infected with haplotype B had significantly lower percentage of nymphal survival compared to psyllids infected with haplotype A. Although overall gene expression across Lso genome was similar between the two Lso haplotypes, differences in the expression of key candidate genes were found. Among the 16 putative type IV effector genes tested, four of them were differentially expressed between Lso haplotypes, while no differences in gene expression were measured by qPCR or transcriptomic analysis for the rest of the genes. This study provides new information regarding the pathogenesis of Lso haplotypes in their insect vector.
ISSN: 2235-2988

hal-01512244
https://hal.archives-ouvertes.fr/hal-01512244
https://hal.archives-ouvertes.fr/hal-01512244/document
https://hal.archives-ouvertes.fr/hal-01512244/file/Yao%202016%20Frontiers%20in%20Cellular%20and%20Infection%20Microbiology_%7BD6ACF6EB-9794-4F27-AB84-9EF4099B6D78%7D.pdf
DOI : 10.3389/fcimb.2016.00062

Éditeur(s) : HAL CCSD
Résumé : International audience
Les auteurs ont mesuré l'augmentation de température dans les spadices de deux espèces de Monstera: Monstera adansonii Schott et Monstera deliciosa Liebm. La température des spadices a été enregistrée parallèlement à la description du cycle floral (mouvement de la spathe, production d'odeur, libération de pollen et de résine) sur des plantes cultivées au Jardin botanique de Montréal. Les cycles floraux et thermogénétiques, qui sont identiques pour les deux espèces, durent 96 heures et s'étendent sur près de cinq jours. Quand la floraison débute (premier jour, phase femelle), la température du spadice augmente légèrement au dessus de la température ambiante jusqu'au début de la phase mâle. Le matin du cinquième jour, quand la température ambiante est à son plus bas, la température du spadice commence à augmenter et atteint un maximum en même temps que le pollen est libéré. Le type de cycles floraux et thermogénétiques indique que M adansonii et M deliciosia pourraient être pollinisés par des insectes (probablement des coléoptères) arrivant avant que la spathe soit complètement déroulée et repartant au moment de la libération du pollen.
Bulletin de la société d'histoire naturelle de Toulouse

hal-01086661
https://hal-agroparistech.archives-ouvertes.fr/hal-01086661

Éditeur(s) : HAL CCSD Universidad Complutense de Madrid
Résumé : The Lodève Permian synrift sequence is represented by thick stacked climate-controled playa cycles which have been constrained by structural, sedimentological, geochemical and paleontological processes. The present paper merges the different results in order to better constrain the dynamics and palaeoecologycal evolution of the playa system from Late Cisuralian to Early Lopingian time. In this depositional environment, thining upwards sheet-flood sequences represent flooding events; they are relayed by ephemeral ponding, suspension settling and limited carbonate precipitation accompanied by large amounts of shallow to subaerial sedimentary structures... (Ver más) (current and wind ripples, desiccation cracks, rain drops, etc.). The aridity of the climate contrasts with the surprising abundance of the fauna encountered into carbonate-rich silty-clay playa-lake deposits. Ephemeral pools are colonized by numerous shellfish: Choncostraca, Triopsids, and Insects, which led to intense burrowing of the overbank deposits (Scoyenia facies). Tetrapods are common and dominated by several types of reptiles after footprints: Pelycosauria, Parareptilia and Lepidosauria in the Rabejac Fm, and Mammalian reptiles (Therapsida) on the top of the fluvial deposits of the Salagou Fm near La Lieude farm. In addition, elements of a weighty herbivorous Pelycosaurian and a small amphibian Tupilakosaurid, only described in the Triassic before, have been also found in the Upper part of the Permian series of this sector.
ISSN: 1698-6180

hal-00411539
https://hal.archives-ouvertes.fr/hal-00411539

Éditeur(s) : HAL CCSD Taylor & Francis
Résumé : International audience
ISSN: 1559-2316

hal-01086786
https://hal-agroparistech.archives-ouvertes.fr/hal-01086786
DOI : 10.4161/psb.4.9.9423

Éditeur(s) : HAL CCSD
Résumé : Neotropical forests shelter an astonishing and underrated biodiversity. The integrity and stability of these natural ecosystems are threatened by human-induced environmental changes. Therefore, highlighting the determinants of ecosystem functioning, be they natural or anthropogenic, is a daunting but paramount scientific challenge. The intrinsic complexity of highly diversified ecosystems arouses both conceptual and logistical difficulties, which we handle, by manipulating tiny ecosystems, the tank bromeliads. The leaves of tank bromeliads form wells that hold rainwater and intercept leaf litter, allowing for a simple invertebrate aquatic community to thrive. These plants can be exhaustively sampled, are naturally replicated, and widely distributed.From local to biogeographic scales, this thesis aims at understanding how these communities respond to the natural heterogeneity of Amazonian forests, and at predicting the impacts of human-induced disturbances on the structure and functioning of these communities, using in situ and lab experiments. Particular focus is attributed to the influence of some aspects of climate changes (e.g., warming, and various precipitations scenarios) on individual physiology, behavior, and trophic interactions.
Les forêts néotropicales accueillent une importante biodiversité encore méconnue. L’intégrité des écosystèmes naturels est menacée par les changements environnementaux (e.g., réchauffement climatique, destruction des habitats), par conséquent, identifier les facteurs structurants, naturels et anthropiques, du fonctionnement des écosystèmes, représente un défi scientifique crucial. L’inhérente complexité de ces milieux diversifiés pose de nombreux problèmes conceptuels et logistiques comme un échantillonnage exhaustif et/ou l’identification des espèces. Les broméliacées à réservoirs sont des écosystèmes miniatures adéquats pour pallier ces difficultés, car elles retiennent de l’eau de pluie et accumulent de la matière organique au creux de leurs feuilles, permettant ainsi de supporter des réseaux trophiques simples d’invertébrés aquatiques. Elles peuvent être échantillonnées exhaustivement, ont une forte abondance locale, et une large aire de répartition. De l’échelle locale à biogéographique, les travaux de cette thèse visent d’abord à comprendre comment ces communautés se structurent en réponse à l’hétérogénéité naturelle des forêts amazoniennes (e.g., ouverture de la canopée, fluctuations climatiques saisonnières), puis tente de prédire, par le biais d’expérimentations in situ et au laboratoire les réponses structurelles et fonctionnelles de ces communautés à divers scénarios de changement climatique. Une attention particulière a été portée sur l’impact de la température et des précipitations sur la physiologie et le comportement d’espèces clefs, et sur les interactions trophiques au sein des communautés.
https://tel.archives-ouvertes.fr/tel-01405025

NNT : 2015YANE0003
tel-01405025
https://tel.archives-ouvertes.fr/tel-01405025
https://tel.archives-ouvertes.fr/tel-01405025/document
https://tel.archives-ouvertes.fr/tel-01405025/file/These-DEZERALD-Diffusion.pdf

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant-plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant-myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca-Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees' fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree.
ISSN: 0028-1042

hal-00818203
https://hal.archives-ouvertes.fr/hal-00818203
DOI : 10.1007/s00114-010-0710-y
PUBMED : 20730522

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 0378-1127

hal-01087219
https://hal-agroparistech.archives-ouvertes.fr/hal-01087219
DOI : 10.1016/j.foreco.2008.09.010

Éditeur(s) : HAL CCSD
Résumé : Biogenic volatile organic compound (BVOCs) emissions play an important role in regional air quality and global atmospheric chemistry. In addition, these natural VOC emissions serve important biological functions including attracting and repelling pollinators and herbivores. Some biological organisms use ambient air as a communication medium and the oxidation of these compounds brings about the concentration gradients sensed by insects and other organisms. Isoprene is the predominant BVOC emitted by vegetation and tropical forests are the dominant global source. This compound is very reactive in the atmosphere and contributes to the reactions that control tropospheric oxidant concentrations and thus the concentrations and lifetimes of longer-lived species. This paper presents a study on the seasonal variations in isoprene and some other significant BVOCs such as µ-pinene, µ-pinene, limonene, e-µ ocimene and longifolene, measured at the Guyaflux Tower located in a wet tropical forest in Paracou French Guiana (5o16´54´´N, 52o54´44´´W), during the year of 2011, using the Relaxed Eddy Accumulation technique at approximately 20 meters high above the canopy. The results show a lower concentration of isoprene during the month of February and March which correspond to the wet season with an average of 0,545 µg/m3 and 0,341 µg/m3, respectively followed by a slight increase in middle April (still wet season) and a higher concentration later in mid-June. The same behavior was observed for µ-pinene with higher concentrations for the same periods as isoprene however with a smaller increase. All the other compounds had concentrations below 1 µg/m3during the whole year: The monoterpene, e-µ ocimene, was observed and is known as a stress compound but the vegetation at the site did not face any known severe stress condition such as excessive drought or flooding. Concerning the fluxes, the results showed that just a small amount of BVOCs were deposited by wet or dry process and the majority of them were released in the atmosphere. Isoprene was by far the biogenic volatile organic compound with the highest concentration and flux, followed by alpha-pinene. The lowest concentration and flux rate for all the studied compounds was observed during the months of March and late July and beginning of August indicating a lower production of those BVOCs by vegetation during those periods. Previous limited studies in Amazonia and the Congo suggested that a higher concentration and flux rate of isoprene and µ-pinene should be expected during the dry season with lower emissions during the wet season, which is in relative agreement with what was observed at this tropical forest site in French Guiana. The exceptions were observed in April and June which correspond to a long wet period in which the concentration of isoprene and µ-pinene increased more than it was expected for this time of the year. The observations will be compared to output from the global chemistry transport model CAM-chem, which includes the MEGAN biogenic emissions model.
10th EGU General Assembly
vienne, Austria

hal-01204214
https://hal.archives-ouvertes.fr/hal-01204214
PRODINRA : 276525

Éditeur(s) : HAL CCSD Museum Nationale d'Histoire Naturelle Paris
Résumé : International audience
ISSN: 1280-9551

hal-01084016
https://hal-agroparistech.archives-ouvertes.fr/hal-01084016
DOI : 10.5252/z2009n4a8

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Perinatal exposure to endocrine-disrupting chemicals may affect thyroid hormones homeostasis and impair brain development. Chlordecone, an organochlorine insecticide widely used in the French West Indies has known estrogenic and progestin properties, but no data is available, human or animal, on its action on thyroid hormone system. Our aim was to evaluate the impact of perinatal exposure to chlordecone on the thyroid hormone system of a sample of infants from the Timoun mother-child cohort in Guadeloupe and their further neurodevelopment. Chlordecone was measured in cord blood and breast milk samples. Thyroid stimulating hormone (TSH), free tri-iodothyronine (FT3), free thyroxine (FT4) were determined in child blood at 3 months (n=111). Toddlers were further assessed at 18 months using an adapted version of the Ages and Stages Questionnaire (ASQ). Cord chlordecone was associated with an increase in TSH in boys, whereas postnatal exposure was associated with a decrease in FT3 overall, and in FT4 among girls. Higher TSH level at 3 months was positively associated with the ASQ score of fine motor development at 18 months among boys, but TSH did not modify the association between prenatal chlordecone exposure and poorer ASQ fine motor score. Perinatal exposure to chlordecone may affect TSH and thyroid hormone levels at 3 months, differently according to the sex of the infant. This disruption however did not appear to intervene in the pathway between prenatal chlordecone exposure and fine motor child development.
ISSN: 0013-9351

hal-01134317
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134317
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134317/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134317/file/Perinatal%20exposure%20to%20chlordecone_accepted.pdf
PUBMED : 25747818

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Plants often rely on external, mutualistic partners to survive and reproduce in resource-limited environments or for protection from enemies. Such interactions, including mycorrhizal symbioses and ant-plant associations, are widespread and play an important role at the ecosystem and community levels. In ant-plant mutualisms, the plants may benefit from both the protection provided by the presence of ants and from the nutrients absorbed from insect debris. However, the role of third partners in plant nutrition, particularly ant-associated fungi, has never before been demonstrated. 2. We investigate this issue in the ant-plant Hirtella physophora. In this model system, Allomerus decemarticulatus ants are involved in two, highly specific interactions: first, with their host plant, and, secondly, with a fungus that they actively manipulate. Moreover, the ants combine both plant trichomes and fungal hyphae to make a trap to capture prey. 3. We empirically demonstrate the existence of a third type of interaction between the fungus and the plant through the use of both experimental enrichments with stable isotopes (15N) and histological approaches. The fungus growing in the galleries plays a role in providing nutrients to the host plant, in addition to the structural role it plays for the ants. Fungus-facilitated nitrogen uptake occurs mainly in old domatia, where abundant hyphae are in close contact with the plant cells. Whether the fungi inside the domatia and those in the galleries are the same is still uncertain. 4. Synthesis. Together, our results show that a fungal partner in an ant-plant mutualism can benefit the plant by improving its nutrient uptake, and they demonstrate the existence of a true tripartite mutualismin this system. Our results add further evidence to the notion that interpretations of some ant-plant symbioses as purely protective mutualisms have overlooked these nutritional aspects.
ISSN: 0022-0477

hal-00818792
https://hal.archives-ouvertes.fr/hal-00818792

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Mutualisms, or interactions between species that lead to net fitness benefits for each species involved, are stable and ubiquitous in nature mostly due to "byproduct benefits" stemming from the intrinsic traits of one partner that generate an indirect and positive outcome for the other. Here we verify if myrmecotrophy (where plants obtain nutrients from the refuse of their associated ants) can explain the stability of the tripartite association between the myrmecophyte Hirtella physophora, the ant Allomerus decemarticulatus and an Ascomycota fungus. The plant shelters and provides the ants with extrafloral nectar. The ants protect the plant from herbivores and integrate the fungus into the construction of a trap that they use to capture prey; they also provide the fungus and their host plant with nutrients. During a 9-month field study, we over-provisioned experimental ant colonies with insects, enhancing colony fitness (i.e., more winged females were produced). The rate of partial castration of the host plant, previously demonstrated, was not influenced by the experiment. Experimental plants showed higher δ¹⁵N values (confirming myrmecotrophy), plus enhanced vegetative growth (e.g., more leaves produced increased the possibility of lodging ants in leaf pouches) and fitness (i.e., more fruits produced and more flowers that matured into fruit). This study highlights the importance of myrmecotrophy on host plant fitness and the stability of ant-myrmecophyte mutualisms.
PLoS ONE

hal-00913754
https://hal.archives-ouvertes.fr/hal-00913754
https://hal.archives-ouvertes.fr/hal-00913754/document
DOI : 10.1371/journal.pone.0059405
OATAO : 10202

Éditeur(s) : HAL CCSD
Résumé : One critical challenge for plants is to maintain an adequate nutrient supply under fluctuating environmental conditions. This is particularly true for epiphytic species that have limited or no access to the pedosphere and often live in harsh climates. Bromeliads have evolved key innovations such as epiphytism, water-absorbing leaf trichomes, tank habit and Crassulacean acid metabolism (CAM) photosynthesis that enable them to survive under various environmental conditions. Bromeliads encompass diverse ecological types that live on different substrates (they can be terrestrial, epilithic or epiphytic) and vary in their ability to retain water (they can be tank-forming or tankless) and photosynthetic pathway (i.e. C3 or CAM). In this review, we outline the nutritional modes and specializations that enable bromeliads to thrive in a wide range of nutrient-poor (mostly nitrogen-depleted) environments.Important FindingsBromeliads have evolved a great diversity of morphologies and functional adaptations leading to the existence of numerous nutritional modes. Focusing on species that have absorptive foliar trichomes, we review evidence that bromeliads have evolved multi-faceted nutritional strategies to respond to fluctuations in the supply of natural nitrogen (N). These plants have developed mutualistic associations with many different and functionally diverse terrestrial and aquatic microorganisms and metazoans that contribute substantially to their mineral nutrition and, thus, their fitness and survival. Bacterial and fungal microbiota-assisted N provisioning, protocarnivory, digestive mutualisms and myrmecotrophic pathways are the main strategies used by bromeliads to acquire nitrogen. The combination of different nutritional pathways in bromeliads represents an important adaptation enabling them to exploit nutrient-poor habitats. Nonetheless, as has been shown for several other vascular plants, multiple partners are involved in nutrient acquisition indicating that there have been convergent adaptations to nutrient scarcity. Finally, we point out some gaps in the current knowledge of bromeliad nutrition that offer fascinating research opportunities.
ISSN: 1752-9921

hal-01532637
https://hal.archives-ouvertes.fr/hal-01532637
DOI : 10.1093/jpe/rtv052
PRODINRA : 384521