A new bathymodioline mussel symbiosis at the Juan de Fuca hydrothermal vents
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Cold seep
Chemosynthesis
Deep‐sea environments are, in some cases, largely unexplored ecosystems, where life thrives driven by the geochemical features of each location. Among these environments, chemosynthesis‐based ecosystems, in the Mid Atlantic Ridge, have an exclusive combination of high depth, high sulfur, and high methane concentrations. This is believed to modulate the biological composition of vent communities and influence the overall vent animal transcriptional activity of genes involved in adaptation processes to extreme environments. This opens, thus, the possibility of finding gene expression signatures specific to a given hydrothermal vent field. Regardless of the extreme physicochemical conditions that characterize deep‐sea hydrothermal vents, the animals dwelling around the vent sites exhibit high productivity and thus must cope with toxic nature of vent surrounding, seemingly deleterious to the animals, while developing surprisingly successful strategies to withstand adverse environmental conditions, including environmental microbes and mechanical stress whether ensuing from animal predation or venting activity. The deep‐sea vent mussel Bathymodiolus azoricus has adapted well to deep‐sea extreme environments and represents the dominating faunal community from hydrothermal vent sites in the Mid‐Atlantic Ridge, owing its successful adaptation and high biomasses to specialized exploitation of methane and sulfide sources from venting activity. Its extraordinary capabilities of adapting and thriving in chemosynthesis‐based environments, largely devoid of photosynthetic primary production and characterized by rapid geochemical regime changes are due to symbiotic associations with chemosynthetic bacteria within its large gills. In an attempt to understand physiological reactions in animals normally set to endure extreme deep‐sea environments, our laboratory has undertaken, for the last few years, a series of investigations, aimed at characterizing molecular indicators of adaptation processes of which components of the host defense system has received most attention. This study reviews recent advances on the characterization of molecules and genes participating in immune reactions, using in vivo and ex vivo models, to elucidate cellular and humoral defense mechanisms in vent mussels and the strategies they have adopted to survive under extreme environments.
Chemosynthesis
Extreme environment
Mytilidae
Geomicrobiology
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Cold seep
Chemosynthesis
Petroleum seep
Adductor muscles
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The animal communities associated with the deep-sea reducing environment have been studied for almost 30 years, but until now only a single species of ophiuroid, Ophioctenella acies , has been found at both hydrothermal vents and methane cold seeps. Since the faunal overlap between vent and seep communities is small and many endemic species have been found among other taxa (e.g. Mollusca, Crustacea), additional species of ophiuroids were expected at previously unstudied sites. Chemical compositions at reducing sites differ greatly from the nearby bathyal environment. Generally, species adapted to chemosynthetic environments are not found in non-chemosynthetic habitats, but occasional visitors of other bathyal species to vent and seep sites have been recorded among many taxa except ophiuroids. This paper presents an analysis of the ophiuroid fauna found at hydrothermal vents and non-reducing nearby sites on the Mid-Atlantic Ridge and on methane cold seeps in the Gulf of Mexico, at Blake Ridge off South Carolina and south of Barbados. In addition to O. acies , four species were found at vents, Ophiactis tyleri sp. nov., Ophiocten centobi , Ophiomitra spinea and Ophiotreta valenciennesi rufescens . While Ophioctenella acies appears to be restricted to chemosynthetic areas, the other four species were also found in other bathyal habitats. They also occur in low numbers (mostly single individuals), whereas species adapted to hydrothermal areas typically occur in large numbers. Ophioscolex tripapillatus sp. nov. and Ophiophyllum atlanticum sp. nov. are described from nearby non-chemosynthetic sites. In a cold seep south of Barbados, three species of ophiuroids were found, including Ophioctenella acies , Amphiura sp., Ophiacantha longispina sp. nov. and Ophioplinthaca chelys . From the cold seeps at Blake Ridge and the Gulf of Mexico, Ophienigma spinilimbatum gen. et sp. nov. is described, likely restricted to the reducing environment. Ophiotreta valenciennesi rufescens occurred abundantly among Lophelia corals in the Gulf of Mexico seeps, which is the first record of this species from the West Atlantic. Habitat descriptions complement the taxonomic considerations, and the distribution of the animals in reducing environments is discussed.
Chemosynthesis
Bathyal zone
Cold seep
Petroleum seep
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Chemosynthesis
Cold seep
Petroleum seep
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Problems with the identification of tubular fossils from ancient hydrothermal vent and cold seep deposits have hindered understanding of the evolutionary history of vent and seep communities. This thesis aims to (1) improve knowledge of lesser-studied tubicolous annelids occupying vents and seeps, (2) study the diversity of tubes at vents and seeps, (3) investigate the fossilisation of tubes within modern vents and seeps, (4) better interpret the fossil record, and (5) provide insights into the palaeoecology these environments. Results presented here on investigations of Sclerolinum contortum, a species belonging to a little- studied genus of the major vent/seep dwelling annelid family Siboglinidae, demonstrate that it exhibits tube morphological plasticity, wide habitat preferences and a global distribution spanning the Arctic to the Southern Ocean. These results also suggest that this species has dispersed throughout this range using chemosynthetic habitats as stepping stones. A detailed investigation of the full mineralisation process of Alvinella (Alvinellidae) tubes at modern hydrothermal vents shows that these tubes are fossilised by pyrite and silica that template organic tube layers, and that microorganisms living on tube surfaces are also exceptionally well-preserved alongside the tubes. No known ancient vent tube fossils resemble mineralised Alvinella tubes. A major morphological and compositional comparison of both modern and fossil tubes from vents and seeps revealed that two fossil tube types from the Mesozoic were likely made by vestimentiferans (Siboglinidae), suggesting that this major vent and seep annelid lineage has a longer history within vents and seeps than proposed by molecular clock age estimates. This analysis also demonstrates the need for greater caution in assigning affinities to fossil vent and seep tubes. Finally, this thesis reports the remarkable preservation of filamentous microorganisms on the walls of Silurian vent tube fossils, giving the first insights into ecological associations between microbes and metazoans within the oldest known hydrothermal vent community.
Chemosynthesis
Cold seep
Taphonomy
Petroleum seep
Paleoecology
Annelid
Tetrapod (structure)
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Chemoautotrophic symbiotic bacteria of organisms inhabiting the hydrothermal vent and cold seep communities in the deep-sea were histologically examined using a transmission electron microscopy on symbionts of Calyptogena sp. A from the site east off Miyako (water depth at 1,700m), Calyptogena sp. B from the Calyptogena Site, vestimentiferan tube worm Lamellibrachia sp. A from Sagami Bay Lamellibrachia sp. B from Calyptogena Site of the Iheya Ridge, pogonophoran tube worms from Sagami Bay and Calyptogena Site of the Iheya Ridge, Bathymodiolus spp. from Sagami Bay, the Iheya Ridge and the North Fiji Basin. Based on the morphological microscopic observations, two species of Calyptogena from Miyako and the Iheya Ridge, two species of vestimentiferan tube worms from Sagami Bay and the Iheya Ridge, and pogonophoran tube worms from Sagami Bay and the Iheya Ridge observed to host sulfur-oxidizing symbiotic bacteria. The occurrence of chemosynthetic symbionts in these organisms was expected beforehand based on the ecological observations of their habitats. Other members of these groups from the world oceans, and the recent advances in the symbiosis at vents and seeps were reviewed.
Chemosynthesis
Cold seep
Symbiotic bacteria
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Background Here, insight is provided into the present knowledge on free-living nematodes associated with chemosynthetic environments in the deep sea. It was investigated if the same trends of high standing stock, low diversity, and the dominance of a specialized fauna, as observed for macro-invertebrates, are also present in the nematodes in both vents and seeps. Methodology This review is based on existing literature, in combination with integrated analysis of datasets, obtained through the Census of Marine Life program on Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss). Findings Nematodes are often thriving in the sulphidic sediments of deep cold seeps, with standing stock values ocassionaly exceeding largely the numbers at background sites. Vents seem not characterized by elevated densities. Both chemosynthetic driven ecosystems are showing low nematode diversity, and high dominance of single species. Genera richness seems inversely correlated to vent and seep fluid emissions, associated with distinct habitat types. Deep-sea cold seeps and hydrothermal vents are, however, highly dissimilar in terms of community composition and dominant taxa. There is no unique affinity of particular nematode taxa with seeps or vents. Conclusions It seems that shallow water relatives, rather than typical deep-sea taxa, have successfully colonized the reduced sediments of seeps at large water depth. For vents, the taxonomic similarity with adjacent regular sediments is much higher, supporting rather the importance of local adaptation, than that of long distance distribution. Likely the ephemeral nature of vents, its long distance offshore and the absence of pelagic transport mechanisms, have prevented so far the establishment of a successful and typical vent nematode fauna. Some future perspectives in meiofauna research are provided in order to get a more integrated picture of vent and seep biological processes, including all components of the marine ecosystem.
Chemosynthesis
Cold seep
Dominance (genetics)
Meiobenthos
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Symbiosis of chemoautrophic bacteria with the members of hydrothermal vent and cold seep communities in the deep-sea were examined by histology using transmission electron microscopy; Bathymodiolus spp. from Sagami Bay, the Iheya Ridge and the North Fiji Basin; and Ifremeria nautilei from the North Fiji Basin. Two species of Bathymodiolus, each from Sagami Bay and the Iheya Ridge harbored methane-oxidizing symbionts within their gill tissues. Vent gastropod Ifremeria nautilei from the hydrothermal vents of the North Fiji Basin housed two types of symbionts; one sulfur-oxidizing type and the other methane-oxidizing type. The occurrence of chemosynthetic symbionts in these organisms were expected before-hand based on the ecological observations of their habit. The other members of these groups from world oceans and the recent advances in the symbiosis of the vent and seep communities were reviewed.
Chemosynthesis
Petroleum seep
Cold seep
Seabed
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