Evolution des adaptations respiratoires des Polynoidae des sources hydrothermales profondes

The Polynoidae (polychaeteous annelids) are found in all marine environments: in polar, temperate and tropical environments, and in coast areas, as well as in the great abyssal depths, including at deep hydrothermal vents and cold seeps. This diversity of habitats and the great number of specie represent a very good opportunity for comparative approaches to study adaptation in a controlled phylogenetic context. If all known species possess neuroglobin, only hydrothermal ones have hemoglobin circulating freely within their coelomic fluid. These hemoglobins exhibit a diversity of structures (tetradomaine or single-domain subunits) and a diversity of properties. The hemoglobins possess a high affinity for oxygen, which allows polynoids to extract oxygen from the environment, even when environmental concentrations are very low. This capacity allows hydrothermal vent species to maintain a stable oxygen consumption rate at low environmental concentrations (oxyregulators) while littoral species are oxyconformers. The presence of hemoglobin also represents an oxygen storage allowing the polynoids to withstand periods of anoxia experienced near deep-sea hydrothermal vents. They also likely play a role in the physiological temperature tolerance of hydrothermal species by allowing sufficient oxygen supply to meet the temperature-related increase in metabolism.Les Polynoidae (annélides polychètes) sont présents dans tous les environnements marins : dans les milieux polaires, tempérés et tropicaux et sur le littoral, aussi bien que dans les grandes profondeurs abyssales, ou au niveau des sources hydrothermales profondes et des suintements froids. Cette diversité d’habitats et le grand nombre d’espèces font de cette famille un bon candidat pour des approches comparatives d’étude de l’adaptation dans un contexte phylogénétique contrôlé. Si toutes les espèces connues possèdent de la neuroglobine, seules les espèces hydrothermales possèdent de l’hémoglobine circulant librement au sein de leur liquide cœlomique. Ces hémoglobines présentent une diversité de structures (sous-unités tétradomaines ou simple-domaines, monomériques ou multimériques) et de propriétés fonctionnelles. Leurs hémoglobines possèdent une forte affinité pour l’oxygène permettant aux Polynoidae hydrothermaux d’extraire l’oxygène dans leur milieu, même à de très faibles concentrations. Cette capacité permet aux espèces hydrothermales de maintenir leur consommation d’oxygène stable à faible concentration d’oxygène environnemental (oxyrégulateurs), alors que les espèces littorales sont des oxyconformeurs. La présence d’hémoglobine représente aussi une réserve d’oxygène permettant de résister aux périodes d’anoxie que peuvent rencontrer les Polynoidae près des sources hydrothermales profondes. Elles jouent également très probablement un rôle dans la tolérance physiologique à la température dont sont capables les espèces hydrothermales en permettant de maintenir un apport suffisant d’oxygène pour suivre l’augmentation du métabolisme lié à la température

Oxygen consumption rates in deep-sea hydrothermal vent scale worms: effect of lifestyle, oxygen concentration, and temperature sensitivity

International audienceDeep-sea hydrothermal vents are a challenging environment inhabited by very specialized species. To reap the benefits of the local primary production, species need to cope with a number of constraints among which low oxygen is probably the most basic. This hypoxia is further complicated by the highly variable temperature these species experience. We studied the response of deep-sea hydrothermal species of scale worms (Annelida, Polynoidae) to varying levels of oxygen and showed that they were capable of compensating a decrease of environmental oxygen concentration (= oxyregulators), down to values of about 30 µmol.l-1. This contrasts with shallow-water temperate species, for which oxygen consumption is directly proportional to its concentration (= oxyconformers). We measured oxygen consumption rates in 11 species from hydrothermal vents, as well as 2 species from the general deep-sea, and compared them to three shallow-water species. Lifestyle (free-living vs. commensal) and habitat of origin (shallow-water, deep-sea, and hydrothermal vent) did not affect oxygen consumption rates. In agreement with thermodynamic expectations, as temperature increases, oxygen consumption increases as well for all species. The sensitivity of oxygen consumption to temperature variation in the shallow-water species is however smaller than that from the deep-sea hydrothermal vent species. This unexpected result could correspond to a pronounced increase of activity (avoidance behavior) in the vent species, which was not observed for the shallow-water species

Hemoglobins are a keystone adaptation for deep-sea hydrothermal vent scaleworms

International audienc

Oxygen consumption rates in deep-sea hydrothermal vent scale worms: Effect of life-style, oxygen concentration, and temperature sensitivity

Deep-sea hydrothermal vents are a challenging environment inhabited by very specialized species. To reap the benefits of the local primary production, species need to cope with a number of constraints among which low oxygen is probably the most basic. This hypoxia is further complicated by the highly variable temperature these species experience. We studied the response of deep-sea hydrothermal species of scale worms (Annelida, Polynoidae) to varying levels of oxygen and showed that they were capable of compensating a decrease of environmental oxygen concentration (= oxyregulators), down to values of about 30 μmol l−1. This contrasts with shallow-water temperate species, for which oxygen consumption is directly proportional to its concentration (= oxyconformers). We measured oxygen consumption rates in 11 species from hydrothermal vents, as well as 2 species from the general deep-sea, and compared them to three shallow-water species. Life-style (free-living vs. commensal) and habitat of origin (shallow-water, deep-sea, and hydrothermal vent) did not affect oxygen consumption rates. In agreement with thermodynamic expectations, as temperature increases, oxygen consumption increases as well for all species. The sensitivity of oxygen consumption to temperature variation in the shallow-water species is however smaller than that from the deep-sea hydrothermal vent species. This unexpected result could correspond to a pronounced increase of activity (avoidance behaviour) in the vent species, which was not observed for the shallow-water species

Active hydrothermal vents in the Woodlark Basin may act as dispersing centres for hydrothermal fauna

Here we report the discovery of a high-temperature hydrothermal vent field on the Woodlark Ridge, using ship-borne multibeam echosounding and Remotely Operated Vehicle (ROV) exploration. La Scala Vent Field comprises two main active areas and several inactive zones dominated by variably altered basaltic rocks, indicating that an active and stable hydrothermal circulation has been maintained over a long period of time. The Pandora Site, at a depth of 3380 m, is mainly composed of diffuse vents. The Corto site, at a depth of 3360 m, is characterized by vigorous black smokers (temperature above 360 °C). The striking features of this new vent field are the profusion of stalked barnacles Vulcanolepas sp. nov., the absence of mussels and the scarcity of the gastropod symbiotic fauna. We suggest that La Scala Vent Field may act as a dispersing centre for hydrothermal fauna towards the nearby North Fiji, Lau and Manus basins