Letteratura scientifica selezionata sul tema "Alvinellidae"

Examination of all the specimens collected from deep hydrothermal vents in the eastern Pacific allowed us to describe two new species and one new subspecies belonging to the genus Paralvinella Desbruyères and Laubier, 1982: P. pandorae sp.n., P. palmiformis sp. n., and P. pandorae irlandei ssp. n. Alvinella pompejana is split into two species, A. pompejana and A. caudata sp.n., based on to morphological and biochemical data. The six species and subspecies of Alvinellinae (Polychaeta: Ampharetidae) are well separated from all other terebellomorph species by the absence of differentiation between thorax and abdomen. We propose here the erection of a new family, Alvinellidae, which seems to be primitive within the order Terebellida. All known alvinellids are strictly associated with deep hydrothermal vent phenomena.

Polychaetes of the family Alvinellidae (Terrebellida) are endemic to hydrothermal vent communities. A new species from the Juan de Fuca and Gorda ridges in the Northeast Pacific is described; aspects of its buccal appendages, segment number, and uncini placement are unique. Because of initial confusion with a sympatric species, Paralvinella palmiformis Desbruyères and Laubier, protein mobilities were examined to differentiate the species electrophoretically with reference to a third alvinellid, Alvinella pompejana. Among the 17 loci scored, fewer than a quarter of the alleles were present in the two Paralvinella species; Paralvinella sulfincola n.sp. has several diagnostic allozymes. This new species inhabits tubes on the sides of active smoker chimneys and migrates upward as the chimney grows. Individuals are recorded within 1 cm of hydrothermal fluids at temperatures in excess of 300 °C; the species appears to have several molecular adaptations to high ambient temperatures. The Alvinellidae form a fascinating group within which to study phylogenetic and selective processes.

A phylogenetic analysis of the polychaete clade Terebelliformia (Terebellida) was undertaken in order to test monophyly of families and subfamilies and to determine their affinities. Parsimony analyses of 41 terebelliform species with outgroup Owenia fusiformis and 46 morphological characters yielded 106–144 most parsimonious trees with length 250, consistency index=0·432, retention index=0·659 and rescaled consistency index=0·285. Monophyly was indicated for Alvinellidae, Ampharetidae, Terebellidae and Trichobranchidae and the terebellid subfamily Polycirrinae. Monophyly of Terebellidae is supported by the presence of a ridge-like tentacular membrane. Monophyly of Polycirrinae is supported by the loss of branchiae, trilobed upper lip, pinnate secondary notochaetae and ventro-lateral pads. Recognition of Polycirrinae renders taxa in the other terebellid subfamilies—Terebellinae and Thelepodinae—paraphyletic. Our results do not support previous classifications that placed Trichobranchidae as a subfamily of Terebellidae; rather it should be considered equal in rank with Alvinellidae, Ampharetidae, Terebellidae and Pectinariidae. The following relationships were obtained: (Trichobranchidae ((Alvinellidae, Ampharetidae) (Pectinariidae, Terebellidae))). This is the first time a Pectinariidae–Terebellidae sister group relationship has been found; it is supported by the synapomorphic presence of ventral glandular shields.

Terebellomorpha is a clade of predominantly tube-dwelling polychaetes, some of whose species are very abundant and whose habitats range from shallow to very deep waters. The group contains five families (Terebellidae, Ampharetidae, Pectinariidae, Trichobranchidae and Alvinellidae). This study of their inter-relationships uses DNA sequence data from five gene segments. Including outgroups, sequences were available for 15 species for 15 U2 snRNA, 14 for Histone H3, 23 for the D1 expansion region of 28S rDNA, 15 for the D9-10 region of 28S rDNA and 17 for subunit I of cytochrome oxidase. Outgroups included representatives of the polychaete families Cirratulidae, Sabellidae and Siboglinidae, and the clitellate Lumbricus. These sequences include eight GenBank entries for 28S D1 and one for CO1.Generally, and in all analyses restricted to the data collected in this laboratory, but including all of these, Terebellomorpha is monophyletic. Within Terebellomorpha, the single maximum parsimony tree indicates that Alvinellidae (all data from GenBank) belongs to a clade with Terebellidae and some Trichobranchidae, contradicting morphological expectations. Terebellidae is paraphyletic with respect to Trichobranchus, this being associated with the subfamily Thelepodinae. The second trichobranchid genus Terebellides (for which only 28S D1 data is available from GenBank) is topologically very distinct to Trichobranchus. Additional data are needed to establish the family's monophyly. Also within Terebellidae, subfamily Terebellinae is paraphyletic with respect to Polycirrinae, supporting the suggestion that this subfamily's morphological simplicity is derived.

Terebelliformia—“spaghetti worms” and their allies—are speciose and ubiquitous marine annelids but our understanding of how their morphological and ecological diversity evolved is hampered by an uncertain delineation of lineages and their phylogenetic relationships. Here, we analyzed transcriptomes of 20 terebelliforms and an outgroup to build a robust phylogeny of the main lineages grounded on 12,674 orthologous genes. We then supplemented this backbone phylogeny with a denser sampling of 121 species using five genes and 90 morphological characters to elucidate fine-scale relationships. The monophyly of six major taxa was supported: Pectinariidae, Ampharetinae, Alvinellidae, Trichobranchidae, Terebellidae and Melinninae. The latter, traditionally a subfamily of Ampharetidae, was unexpectedly the sister to Terebellidae, and hence becomes Melinnidae, and Ampharetinae becomes Ampharetidae. We found no support for the recently proposed separation of Telothelepodidae, Polycirridae and Thelepodidae from Terebellidae. Telothelepodidae was nested within Thelepodinae and is accordingly made its junior synonym. Terebellidae contained the subfamily-ranked taxa Terebellinae and Thelepodinae. The placement of the simplified Polycirridae within Terebellinae differed from previous hypotheses, warranting the division of Terebellinae into Lanicini, Procleini, Terebellini and Polycirrini. Ampharetidae (excluding Melinnidae) were well-supported as the sister group to Alvinellidae and we recognize three clades: Ampharetinae, Amaginae and Amphicteinae. Our analysis found several paraphyletic genera and undescribed species. Morphological transformations on the phylogeny supported the hypothesis of an ancestor that possessed both branchiae and chaetae, which is at odds with proposals of a “naked” ancestor. Our study demonstrates how a robust backbone phylogeny can be combined with dense taxon coverage and morphological traits to give insights into the evolutionary history and transformation of traits.

The morphology of terebelliform polychaetes was investigated for a phylogenetic study focused on Terebellidae. For this study, specimens belonging to 147 taxa, preferably type material or specimens from type localities or areas close to them, were examined under stereo, light and scanning electron microscopes. The taxa examined were 1 Pectinariidae, 2 Ampharetidae, 2 Alvinellidae, 8 Trichobranchidae, and 134 Terebellidae, which included 8 Polycirrinae, 15 Thelepodinae, and 111 Terebellinae. A comparison of the morphology, including prostomium, peristomium, anterior segments and lobes, branchiae, glandular venter, nephridial and genital papillae, notopodia and notochaetae, neuropodia and neurochaetae, and posterior end, was made of all the currently recognized families of terebelliform polychaetes, with special emphasis on Terebellidae. A discussion of the characters useful to distinguish between genera is given. This character set will be used in a subsequent phylogenetic study (Nogueira & Hutchings in prep.)A morfologia de poliquetas terebeliformes foi analisada para um estudo filogenético focado em Terebellidae. Para esse estudo, foram examinados espécimes pertencentes a 147 táxons, sob estereomicroscópio, microscópio óptico e microscópio eletrônico de varredura, preferencialmente material tipo ou espécimes das localidades tipo, ou de suas proximidades. Os táxons examinados foram 1 Pectinariidae, 2 Ampharetidae, 2 Alvinellidae, 8 Trichobranchidae e 134 Terebellidae, dos quais 8 Polycirrinae, 15 Thelepodinae e 111 Terebellinae. Para este estudo, foi feita a comparação entre a morfologia das famílias de poliquetas terebeliformes atualmente reconhecidas, com especial ênfase em Terebellidae, em relação ao prostômio, peristômio, segmentos anteriores e lobos, brânquias, superfície glandular ventral, papilas nefridiais e genitais, notopódios e notocerdas, neuropódios e neurocerdas, e extremidade posterior. Uma discussão dos caracteres úteis para distinguir os gêneros é fornecida. Este conjunto de caracteres será utilizado para um estudo filogenético subseqüente (Nogueira & Hutchings em preparação).

Terebellomorph polychaetes are reported from hydrothermal vents and cold seeps collected in the Pacific and Atlantic Oceans. Two new species of Terebellidae,Neoamphitrite hydrothermalissp. nov. andStreblosoma kaiasp. nov., are described from hydrothermal vents of the western Pacific. These are the first terebellid species described from hydrothermal vents. New records from hydrothermal vents and cold seeps and new geographical records are presented for nine additional species belonging to Ampharetidae, Alvinellidae, Terebellidae and Trichobranchidae. A synoptic table with diagnostic characters for all species of the genusStreblosomaSars, 1872 is provided. Keys for all terebellomorph species currently known from hydrothermal vents and cold seeps, respectively, are included. Additionally the new combinationNeoamphitrite pachyderma(Hutchings & Glasby, 1988) comb. nov. is proposed.

Les Alvinellidae (annélides polychètes terebellides) constituent une famille d'espèces endémiques des sources hydrothermales profondes, dispersées entre l'océan Pacifique et Indien. Depuis leur découverte avec l'espèce emblématique Alvinella pompejana, le vers de Pompéi, ces animaux ont suscité l'intérêt de la communauté scientifique. En effet, si les sources hydrothermales constituent des environnements réputés extrêmes (gradients de température, absence de photosynthèse, anoxie du milieu, présence de divers métaux et sulfides issus de la percolation du fluide hydrothermale dans la croûte basaltique, pH acide), les Alvinellidae sont parvenus à coloniser des niches écologiques variées et montrent une grande diversité morphologique, physiologique et génétique, inter et intra-espèces. Dans le cadre de cette thèse, nous nous sommes plus particulièrement intéressés aux adaptations permettant à ces vers de faire face à des régimes thermiques contrastés. A. pompejana, par exemple, est thermophile, survivant à des températures proches de 50°C. D'autres espèces en revanche, comme Paralvinella grasslei, sont considérées psychrophiles, vivant à distance des cheminées hydrothermales à des températures entre 10 et 25°C. Plus spécifiquement, nous avons étudié l'acquisition de la thermophilie/psychrophilie au cours de l'évolution de la lignée, en essayant de répondre à la question du phénotype thermique de l'ancêtre des Alvinellidae. Pour cela, nous avons établi la phylogénie moléculaire des Alvinellidae, sur la base des données moléculaires transcriptomiques récupérées pour onze des quatorze espèces de la famille au cours de plusieurs campagnes scientifiques. Ce premier résultat amène à conclure à un ancêtre datant de la fin du Crétacée (entre 60 et 90 millions d'années), déjà présent dans les sources hydrothermales du Pacifique Est. La radiation des Alvinellidae à cette époque a été rapide, en quelques millions d'années, aboutissant à l'apparition de plusieurs espèces présentant de forts taux de tri incomplet de lignée et d'introgression interspécifique. Les résultats de cette phylogénie nous ont permis d'établir le modèle permettant de construire des propositions statistiques de protéines appartenant aux ancêtres de la lignée. Trois protéines ont été choisies, à savoir la malate déshydrogénase cytosolique, la superoxyde dismutase Cu/Zn et une hémoglobine intracellulaire, pour être reconstruites, exprimées et expérimentalement caractérisées. En effet, pour des organismes ectothermes comme les Alvinellidae, il est attendu que les protéines des espèces thermophiles soient en moyenne plus stables thermiquement que les protéines issues des espèces psychrophiles. Ces reconstructions ancestrales nous ont permis de conclure que l'ancêtre de la lignée était un vers déjà adapté aux environnements chauds, et que la psychrophilie de certaines espèces de la lignée est un caractère dérivé acquis plus récemment. Enfin, dans une dernière partie, je me suis intéressé à l'optimisation des modèles de reconstruction des séquences protéiques ancestrales. Ces modèles sont basés sur la diversité des séquences contemporaines et leurs relations phylogénétiques. J'ai essayé d'implémenter ces approches en utilisant deux types d'informations supplémentaires : celles liées aux événements d'insertions/délétions de séquence, et celles concernant l'évolution de la structure secondaire des protéines et la variabilité temporelle des fréquences attendues des résidus aux différentes positions des protéines. Je montre que l'introduction de ces deux derniers types de paramètres dans les méthodes ASR est bénéfique et aboutit à des modèles ayant de meilleures vraisemblances. Toutefois, l'optimisation de ces modèles, nécessairement probabilistes, ne garantit pas un meilleur résultat pour l'expérimentateur, et les limites de ces modèles à estimer l'incertitude des séquences ancestrales inférées sont discutées
The Alvinellidae (Annelida : Terebelliformia) are a species family endemic to deep hydrothermal vents from the Pacific and Indian Oceans. Since the discovery of the emblematic species Alvinella pompejana, the Pompeii worm, these animals have aroused the interest of the scientific community. Although hydrothermal vents are extreme environments (strong temperature gradients, absence of photosynthesis, anoxy, presence of various metals and sulphides due to the percolation of hydrothermal fluid into the basaltic crust, acid pH), the Alvinellidae have managed to colonise a variety of ecological niches and show great morphological, physiological and genetic diversity, both between and within species. In this thesis, we were notably interested in the adaptations that enable these worms to cope with contrasting thermal regimes. A. pompejana, for example, is thermophilic, surviving at temperatures close to 50°C. Other species, however, such as Paralvinella grasslei, are psychrophilic, living further from hydrothermal chimneys at temperatures between 10 and 25°C. More specifically, we studied the acquisition of thermophilia/psychrophilia during the evolution of the lineage, in an attempt to characterize the thermal phenotype of the ancestor of the Alvinellidae. To this end, we have established the molecular phylogeny of the Alvinellidae, based on molecular transcriptomic data recovered for eleven of the fourteen species in the family during several scientific campaigns. This initial result points to an ancestor dating from the end of the Cretaceous (between 60 and 90 million years ago), already present in the hydrothermal vents of the eastern Pacific. The radiation of the Alvinellidae was a quick event, within a few million years, resulting in several species with high rates of incomplete lineage sorting and showing traces of high interspecific introgression. The results of this phylogeny enabled us to establish a model to construct statistical proposals of proteins belonging to the ancestors of the lineage. Three proteins were chosen, namley the cytosolic malate dehydrogenase, the Cu/Zn superoxide dismutase and an intracellular hemoglobin, for reconstruction, expression and experimental characterisation. For ectothermic organisms such as the Alvinellidae, proteins from thermophilic species are expected to be on average more stable at high temperatures compared to their counterparts from psychrophilic species. These ancestral reconstructions allowed us to conclude that the ancestor of the lineage was a worm that was already adapted to warm environments, and that psychrophily of modern-day alvinellid species is a derived character acquired more recently. Finally, I looked at the optimisation of models for reconstructing ancestral protein sequences. These models are based on the diversity of contemporary sequences and their phylogenetic relationships. I tried to implement these approaches using two types of additional information : those linked to sequence insertion/deletion events, and those regarding the evolution of secondary structures of proteins and temporal variability of the expected frequencies of residues at different protein positions. I show that the introduction of these last two types of parameters into ASR methods is beneficial and leads to models with better likelihoods. However, the optimisation of these models, which are necessarily probabilistic, does not guarantee a better result for the experimenter, and the limits of these models to estimate the uncertainty of the inferred ancestral sequences are discussed

Cultural and molecular approaches were used to analyse the microbial assemblages associated to the deep-sea hydrothermal vent polychaete worms of the family Alvinellidae. In a first part of the work, the populations associated to three alvinellid species from the Juan de Fuca Ridge (paralvinella palmiformis, paralvinella pandorae and paralvinella sulfincola) were identified by phylogenetic analyses. A wide microbial diversity was detected, like a great number of new sequences or of sequences belonging to species previously unidentified at deep-sea hydrothermal vents. All the libraries were found to be dominated by sequences affiliated to the e-Proteobacteria. In others respects, fermentative micro-organisms belonging to the Thermococcale, the Thermotogales, the CFB and the Firmicutes were isolated. Autotrophic bacteria reducing sulphur and/or nitrates and belonging to the e-Proteobacteria or to the genus Desulfurobacterium were isolated. Three miro-organisms ,have been characterised : Caminicella sporogenes, Desulfurobacterium crinifex and Caminibacter hydrogeniphilus. In the last part of the work, ultrastructural and chemical anlyses of the atypical macrofilaments formed in culture by desulfurobacterium crinifex were performed. Finally, in situ colonisation experiments of new surfaces were performed in alvinellid habitat. The microbial cohort preceding the Alvinella spp. Settlement and the populations associated to these polychaetes were analysed using cultural and phytogenetic approaches. Thermal and chemical conditions were monitored during the colonisation process. Based on our results, it would seem that the formation of a microbial mat would be necessary to the alvinellid settlement.

299 bacteries heterotrophes ont ete isolees sur des milieux additionnes de metaux. Ces bacteries, qui colonisent l'epiderme et le tube des alvinellidae preleves sur un site hydrothermal du 13#on (dorsale du pacifique oriental), ont ete identifiees comme membres des genres pseudomonas, alteromonas et vibrio. La determination de leur cmi a montre que 92,3% d'entre elles sont resistantes a au moins un des metaux testes et que 57% sont resistantes a plus d'un metal. La capacite de 40 d'entre elles a accumuler les metaux a ete demontree. Une fraction de ces bacteries (19,1%) contient un a cinq plasmides dont les tailles s'echelonnent de 4,6 a 156,9 kb. Les bacteries concernees presentent de fortes resistances pour les metaux testes, et en particulier pour l'arseniate. Elles sont de plus pour la plupart resistances a la penicilinne et au chloramphenicol. Le plasmide le plus frequemment rencontre (45,3 kb) determine la resistance a l'arsenite et a l'arseniate. Ces resistances sont inductibles par chacun de ces composes. La resistance a l'arsenic est egalement inductible chez les souches partiellement curees, ce qui suggere que les plasmides remanents ainsi qu'un ou des genes d'origine chromosomique seraient impliques dans ce mecanisme, l'ensemble des caracteristiques mises en evidence montre l'adaptation de ces micro-organismes a un environnement enrichi en matiere organique et contenant de fortes concentrations en metaux. Leur capacite a accumuler les metaux les rend susceptibles de contribuer au transfert de ces elements toxiques du milieu exterieur vers les cellules epidermiques des polychetes

Une étude sur la distribution et l'évolution des communautés des sources hydrothermales profondes de la dorsale du pacifique oriental à 13°Non a été entreprise à partir des prélèvements et des données iconographiques obtenus au cours de 3 campagnes. Le peuplement se subdivise en 6 unités et se repartit en 3 grands groupes spatio-temporels d'espèces. Un modèle de succession spatio-temporelle de la mégafaune est propose à partir de ces observations. Les espèces ont un cycle court et un recrutement discontinu compatible avec l'évolution rapide du milieu. Leurs populations sont soumises à des extinctions locales et paraissent, pour la plupart, fondées par un petit nombre d'individus. Pour apprécier les processus de dissémination et de spéciation, une étude de la structure génétique des populations de polychètes alvinellidae est effectuée à partir de l'analyse de leur polymorphisme enzymatique. La variabilité génétique est modérée chez le genre Alvinella et élevée chez le genre Paralvinella. Les populations sont à l'équilibre d'Hardy-Weinberg bien que des déficits en hétérozygotes soient observes pour les mêmes locus dans la majorité des populations. Ces résultats permettent de rejeter l'hypothèse d'un effet Wahlund et suggèrent que la sélection naturelle joue en faveur des hétérozygotes. La différenciation génétique des populations est élevée mais ne varie pas avec la distance. Plusieurs génotypes paraissent thermosensibles et pourraient faire l'objet d'une sélection. Ces résultats laissent supposer que la dérive génétique est contre-balancée par la pression sélective du milieu et que l'environnement joue un rôle dans les processus de spéciation chez les Alvinellidae.

L'annélide polychète tubicole Alvinella pompejana, endémique des sources hydrothermales du Pacifique oriental, colonise la paroi des cheminées actives. Dans cet environnement hypervariable, le mélange chaotique de l'eau de mer et du fluide hydrothermal entraîne d'intenses précipitations minérales. Les matrices extracellulaires de cet organisme, et principalement son tube, sont rapidement recouvertes par des dépôts minéraux. L'objectif de ce travail est d'apporter des données sur les interactions de ces organismes avec leur environnement minéral. L'utilisation d'un nouveau système de récolte a permis d'obtenir intacts des biogéoassemblages formés in situ par les précipitations minérales sur les populations d'alvinellidés. Par la suite, la mise au point de méthodes non conventionnelles pour la préparation et l'observation à l'échelle microscopique de matériaux biologiques fortement minéralisés a permis de montrer l'influence réciproque des phases biologiques et minérales. (1) En réponse à la minéralisation rapide de son tube, Alvinella a développé des adaptations qui se traduisent par une capacité de sécrétion de tube et donc de migration le long de la paroi très élevée. Des taux de croissance de 1 cm/jour ont pu être observés. (2) La colonisation de la paroi des cheminées par des communautés biologiques modifie la géochimie locale. La présence des tubes entraîne non seulement la précipitation des minéraux spécifiques (marcassite, FeS2) au contact de leur tube, mais également une compartimentation des minéraux précipités. Alors que la face externe est riche en sulfures de fer, nous avons montré la présence de nanocristaux de sulfures de zinc dans la paroi du tube, quels que soient le degré et le type de minéralisation extérieure. L'observation d'une étroite association spatiale entre ces nanocristaux et les bactéries présentes entre les couches de tube a conduit à l'hypothèse d'une origine microbienne de ces sulfures
Alvinella pompejana is a polychaetous annelid that inhabits deep-sea hydrothermal vent sites along the East Pacific Rise, where it colonizes the walls of actively venting high-temperature chimneys. In this environment, chaotic mixing of hydrothermal fluid and sea water causes abundant mineral precipitations. Extracellular matrix of these organisms, mostly the tube they secrete, are rapidely engulfed in mineral deposits. In situ biogeoassemblages, consisting in alvinellids, tubes and mineral deposits, were collected thank to a new collection device. Non conventional methods were developped for preparation and observation of heavily mineralised biological samples. Use of this method allows the observation of the mutual influence of mineral and biological phases. (1) Alvinella developped adaptations in response to the rapid mineralisation of its tube : high tube secretion rates permit a rapid migration rate along the chimney walls. (2) Presence of the biological communities on the chimney walls can locally modify the geochemistry. Marcasite crust is precipitated specifically under the tubes mass. Furthermore, the tubes occurrence create a partitioning of mineral precipitates. Whereas outer face of the tube is covered by large iron sulfure deposits, we always observed zinc sulfide nanocrystals within the tube wall. Close spatial relationship between these nanocrystals and microorganisms between tube layers leads to the hypothesis of a biologically-induced origin of the sulfides

Ampharetidae are tubicolous, as are most members of Terebelliformia, and share with Alvinellidae and Melinnidae the feature that their multiple grooved palps, usually called tentacles, can be retracted into the mouth. Typically, Ampharetidae are 10 to 60 mm long, though some adults are only a few millimetres long.