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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2006.05.008 Byline: Rui Company (a), Angela Serafim (a), Richard Cosson (b), Aline Fiala-Medioni (c), David Dixon (d), Maria Joao Bebianno (a) Abstract: Hydrothermal vent mussels are exposed continually to toxic compounds, including high metal concentrations and other substances like dissolved sulphide, methane and natural radioactivity. Fluctuations in these parameters appear to be common because of the characteristic instability of the hydrothermal environment. Temporal variation in the antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), total glutathione peroxidases (Total GPx), selenium dependent glutathione peroxidases (Se-GPx)), metallothioneins and lipid peroxidation (LPO) in the gills and mantle of the mussel Bathymodiolus azoricus from Menez-Gwen hydrothermal vent site was evaluated and related to the accumulated metal concentrations (Ag, Cu, Cd, Fe, Mn and Zn) in the tissues. Maximum antioxidant enzyme activities in the gills were detected in the beginning of summer, followed by a gradual decrease throughout the following months. One year after, the levels of antioxidant enzyme activities were similar to those reported one year before. LPO in this tissue exhibited a similar temporal variation trend. A different pattern of temporal variation in antioxidant enzyme activities was observed in the mantle, with a gradual increase from summer to the end of autumn (November). LPO in the mantle exhibited an almost reverse trend of temporal variation to that of antioxidant enzyme activities in this tissue. Antioxidant defences in the gills of B. azoricus were significantly enhanced with increasing concentrations of Ag, Cu and Mn, while negative relationships between antioxidant enzymes and Cd, Cu, Mn and Zn concentrations in the mantle were observed, suggesting different pathways of reactive oxygen species (ROS) production and that these tissues responded differently to the metal accumulation. However, temporal variation in biomarkers of defence and damage were in general similar to coastal bivalve species and can be associated with temporal variations of the physiological status due to reproduction. These variations might also be linked to the highly unstable nature of the hydrothermal environment. Author Affiliation: (a) CIMA, Faculty of Marine and Environmental Sciences, University of Algarve, Campus de Gambelas, 8000 Faro, Portugal (b) ISOMer-UPRES-EA 2663, Laboratoire de Biologie Marine, Faculte des Sciences et Techniques, Universite de Nantes, BP 92208, F-44322 Nantes, France (c) Observatoire Oceanologique, Universite P.M. Curie, BP 44, 66651 Banyuls sur Mer, France (d) Southampton Oceanography Centre, Waterfront Campus, Empress Dock, Southampton SO14 3ZH, UK Article History: Received 7 June 2005; Revised 16 May 2006; Accepted 19 May 2006

Submersible dives along Atalante, Mount Manon, and the volcanoes, A and cyclope were conducted for fauna and sediment sampling. Videoscopic records of the dives were used to study the composition of benthic fauna and spatial distribution of the symbiotic species. Massive methane-rich fluid expulsion patterns through mud volcanoes in the Barbados trench were found to sustain cold seep communities.

The hydrothermal vent communities at Lucky Strike on the Mid-Atlantic Ridge are different from the other vent communities. Dense mussel beds are dominant in the Lucky Strike fauna and cover the surfaces of hydrothermally active sulfides. The mussels occurs in the cracks from where warm sea water flows out. Twenty five invertebrate taxa are observed in this region out of which seven taxa, which includes bathymodiolid mussel and bresiliid shrimp, were previously unknown. Many taxa, which are common in the eastern Pacific vents and western Pacific hydrothermal systems, are absent from this region.

An investigation on the animal communities at depths around 2000 and 3800 m, by deep tow camera surveys during the Hakuho Maru cruise and Nautile dives during the Kaiko-Nankai cruise shows that vesicomyid bivalve molluscs are predominant, C. laubieri and C. kaikoi species along with two very large species of Calyptogena are also present. Ultrastructural features of symbionts, presence of ATP sulfurylase, absence of methanol dehydrogenase activity and abundant sulphur provide suggest sulfur-oxidizing metabolism in the gill. There is limited or no input of fossil carbon and the growth is dependent on water carbon dioxide.

The natural variability of antioxidant enzyme activity (superoxide dismutase (SOD), catalase (CAT), total glutathione peroxidases (Total-GPx) and selenium dependent gluthione peroxidases (Se-GPx)), metallothioneins (MT) concentrations and MT and lipid peroxidation (LPO) in gills and mantle of Bathymodiolus azoricus from Menez-Gwen hydrothermal vent site is studied. The temporal variation in biomarkers of defence and damage are similar to coastal bivalve species and they are linked to the highly unstable nature of the hydrothermal environment.