Mid-Atlantic Ridge Hydrothermal Vent Research Articles

Arsenic speciation in food chains from mid-Atlantic hydrothermal vents

Arsenic concentration and speciation were determined in benthic fauna collected from the Mid-Atlantic Ridge hydrothermal vents. The shrimp species, Rimicaris exoculata, the vent chimney-dwelling mussel, Bathymodiolus azoricus, Branchipolynoe seepensis, a commensal worm of B. azoricus, and the gastropod Peltospira smaragdina showed variations in As concentration and in stable isotope (δ13C and δ15N) signature between species, suggesting different sources of As uptake. Arsenic speciation showed arsenobetaine to be the dominant species in R. exoculata, whereas in B. azoricus and B. seepensis arsenosugars were most abundant, although arsenobetaine, dimethylarsinate, and inorganic arsenic were also observed, along with several unidentified species. Scrape samples from outside the vent chimneys, covered with microbial mat, which is a presumed food source for many vent organisms, contained high levels of total As, but organic species were not detectable. The formation of arsenosugars in pelagic environments is typically attributed to marine algae, and the pathway to arsenobetaine is still unknown. The occurrence of arsenosugars and arsenobetaine in these deep sea organisms, where primary production is chemolithoautotrophic and stable isotope analyses indicate food sources are of vent origin, suggests that organic arsenicals can occur in a food web without algae or other photosynthetic life.

Acquisition of epibiotic bacteria along the life cycle of the hydrothermal shrimp Rimicaris exoculata

The caridean shrimp Rimicaris exoculata dominates the fauna at several Mid-Atlantic Ridge hydrothermal vent sites. This shrimp has an enlarged gill chamber, harboring a dense ectosymbiotic community of chemoautotrophic bacteria associated with mineral oxide deposits. Until now, their acquisition is not fully understood. At three hydrothermal vent sites, we analyzed the epibionts diversity at different moult stages and also in the first stages of the shrimp life (eggs, hatched eggs (with larvae) and juveniles). Hatched eggs associated with young larvae were collected for the first time directly from gravid females at the Logachev vent site during the Serpentine cruise. An approach using 16S rRNA clone libraries, scanning and transmission electron microscopy, and fluorescent in situ hybridization was used. Molecular results and microscope observations indicated a switch in the composition of the bacterial community between early R. exoculata life cycle stage (egg libraries dominated by the Gammaproteobacteria) and later stages (juvenile/adult libraries dominated by the Epsilonproteobacteria). We hypothesized that the epibiotic phylotype composition could vary according to the life stage of the shrimp. Our results confirmed the occurrence of a symbiosis with Gammaproteobacteria and Epsilonproteobacteria, but more complex than previously assumed. We revealed the presence of active type-I methanotrophic bacteria colonizing the cephalothorax of shrimps from the Rainbow site. They were also present on the eggs from the Logachev site. This could be the first 'epibiotic' association between methanotrophic bacteria and hydrothermal vent crustacean. We discuss possible transmission pathways for epibionts linked to the shrimp life cycle.

2-D difference gel electrophoresis approach to assess protein expression profiles in Bathymodiolus azoricus from Mid-Atlantic Ridge hydrothermal vents

Hydrothermal vent mussels Bathymodiolus azoricus are naturally exposed to toxic chemical species originated directly from vent chimneys. The amount of toxic elements varies significantly among vent sites along the Mid-Atlantic Ridge and B. azoricus must be able to adapt to changes in hydrothermal fluid composition, temperature and pressure. The aim of this work was to study changes in the proteome in the "gill-bacteria complex" of mussels B. azoricus from three hydrothermal vent sites with distinct environmental characteristics using 2-D Fluorescence Difference Gel Electrophoresis (2-D DIGE). Results showed that 31 proteins had different expression profiles among vent sites and both cluster and principal component analysis confirm a clear separation of mussels between sites. This suggests the existence of specific parameters grouping individuals from the same hydrothermal site. Protein spots of the more abundant differentially expressed proteins were excised, digested with trypsin and identified by mass spectrometry. All identified proteins (actin, ubiquinone, S-adenosylhomocysteine hydrolase, cysteine peptidases, chaperonin and catalase) have been related previously with oxidative stress conditions and are known to be affected by ROS inducing stressors, including metals. Results point out to specific adaptations at the proteome level of B. azoricus depending on the level of toxicants present in their environment.

Candida oceani sp. nov., a novel yeast isolated from a Mid-Atlantic Ridge hydrothermal vent (−2300 meters)

A novel species in the genus Candida was obtained from deep-sea hydrothermal fields on the Mid-Atlantic Ridge. Strains Mo39, MARY089 and CBS 5307, respectively, isolated from an unidentified deep-sea coral collected near Rainbow hydrothermal vent, from water samples near Menez Gwen hydrothermal field and from the stomach of a marine fish are considered as a novel taxon. Sequence similarities in the D1/D2 region of the 26S rRNA gene indicated that strains Mo39, MARY089 and CBS 5307 have for closest neighbors Candida spencermartinsiae, Candida taylorii, Candida atmosphaerica and Candida atlantica. The strains, respectively, differ from C. spencermartinsiae, C. taylorii, C. atmosphaerica andCandida atlantica by 4, 4.3, 4.3 and 4.7% in the D1/D2 domain. Strains Mo39, MARY089 and CBS 5307 were differentiated from others by differences in the ability to assimilate D: -Gluconate and in the ability to grow at relatively high temperature. Only strain Mo39 displays an optimal growth at 3% sea salts, indicating that this strain is clearly adapted to live in marine conditions. Sequence similarities between strains Mo39, MARY089 and CBS 5307 and related species and differences in the ability to utilize specific carbon compounds revealed that these strains represent a hitherto unknown species. Sexual reproduction was not observed in strains Mo39, MARY089 and CBS 5307. An anamorphic name Candida oceani sp. nov. is proposed for the type strain Mo39(T) (= CBS 11857(T) = DSM 23777(T)) and the two other strains MARY089 and CBS 5307. To our knowledge, this is the first description of a micro-eukaryotic organism including a strain isolated from a deep-sea coral near a hydrothermal ecosystem.

Comparative analysis between protist communities from the deep‐sea pelagic ecosystem and specific deep hydrothermal habitats

Protist communities associated with deep seawater and bivalves from six hydrothermal sites in the Pacific Ocean were characterized by microscopy and molecular rRNA gene surveys (18S rRNA) and compared with planktonic communities from Pacific deep-pelagic seawater (from 500 to 3000 m in depth). Genetic libraries from larger size fractions (>3 µm) of deep-pelagic water were mainly dominated by Dinophyceae, whereas small size fractions (<3 µm) mainly revealed radiolarians and Syndiniales. In contrast, more specific opportunistic detritivores and grazers, mostly belonging to Stramenopiles and Cercozoa, were detected from water surrounding vent chimneys. Protist communities were different in the pallial cavity of the giant hydrothermal bivalves Bathymodiolus thermophilus and Calyptogena magnifica, dominated by Ciliophora (primarily belonging to Phyllopharyngea, Oligohymenophorea and Oligotrichea) and Cercozoa. Interestingly, protist communities retrieved from the pallial cavity liquid of hydrothermal bivalves were remarkably homogeneous along the Southern East Pacific Rise, in contrast to bivalves collected on the Mid-Atlantic Ridge hydrothermal vents and cold seeps from the Gulf of Mexico. Hence, complex protist communities seem to occur inside hydrothermal bivalves, and these metazoa may constitute a stable micro-niche for micro-eukaryotes, including grazers, detritivores, symbionts and potential parasites. From these communities, new lineages within the ciliates may emerge.

Tracing carbon assimilation in endosymbiotic deep-sea hydrothermal vent Mytilid fatty acids by &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C-fingerprinting

Abstract. Bathymodiolus azoricus mussels thrive at Mid-Atlantic Ridge hydrothermal vents, where part of their energy requirements are met via an endosymbiotic association with chemolithotrophic and methanotrophic bacteria. In an effort to describe phenotypic characteristics of the two bacterial endosymbionts and to assess their ability to assimilate CO2, CH4 and multi-carbon compounds, we performed experiments in aquaria using 13C-labeled NaHCO3 (in the presence of H2S), CH4 or amino-acids and traced the incorporation of 13C into total and phospholipid fatty acids (tFA and PLFA, respectively). 14:0; 15:0; 16:0; 16:1(n − 7)c+t; 18:1(n − 13)c+t and (n − 7)c+t; 20:1(n − 7); 20:2(n − 9,15); 18:3(n − 7) and (n − 5,10,13) PLFA were labeled in the presence of H13CO3− (+H2S) and 13CH4, while the 12:0 compound became labeled only in the presence of H13CO3− (+H2S). In contrast, the 17:0; 18:0; 16:1(n − 9); 16:1(n − 8) and (n − 6); 18:1(n − 8); and 18:2(n − 7) PLFA were only labeled in the presence of 13CH4. Some of these symbiont-specific fatty acids also appeared to be labeled in mussel gill tFA when incubated with 13C-enriched amino acids, and so were mussel-specific fatty acids such as 22:2(n − 7,15). Our results provide experimental evidence for the potential of specific fatty acid markers to distinguish between the two endosymbiotic bacteria, shedding new light on C1 and multi-carbon compound metabolic pathways in B. azoricus and its symbionts.

Metal concentrations and metallothionein-like protein levels in deep-sea fishes captured near hydrothermal vents in the Mid-Atlantic Ridge off Azores

The knowledge of metal contamination in deep-sea fishes living in the surroundings of hydrothermal vents is very scarce, along with the detoxification mechanisms that allow them to live near one of the most metal contaminated marine environments. Six deep-sea fish species, although not vent endemic were collected near three Mid-Atlantic Ridge (MAR) hydrothermal vents (Menez Gwen, Lucky Strike and Rainbow) and the gills, muscle and liver were selected for this study due to their importance in metal metabolism and storage. The concentrations of seven metals (Ag, Cd, Cr, Cu, Fe, Mn, and Ni) and a metal-related biomarker (metallothionein-like proteins–MTL) were assessed. Major differences in metal accumulation among fish species are related to their feeding habits and vent site of their capture. The liver and gills are in general the most important tissues for metal accumulation compared to the muscle, but tissue partitioning is very dependent on the fish species considered. Compared to other deep-sea fishes, fish capture in the vicinity of hydrothermal vents accumulates higher amounts of metals in general. However, MTL levels are not considerably different from what is found in commercial coastal fishes, and is poorly correlated with metal concentrations in the tissues. Therefore, MTL may not constitute one major detoxification system for deep-sea species living in the vicinity of three important MAR vent sites.

Sub-lethal effects of cadmium on the antioxidant defence system of the hydrothermal vent mussel Bathymodiolus azoricus

The mussel Bathymodiolus azoricus is one of the most abundant species in the Mid-Atlantic Ridge hydrothermal vents and is continually exposed to the high-temperature venting fluids containing high metal concentrations and enriched in sulphides and methane, which constitute a potential toxic environment for marine species. The aim of this study was to assess the effects of a sub-lethal Cd concentration on the antioxidant defence system of this mussel. B. azoricus were collected at Menez Gwen vent site (37°51'N, 32°31'W) and exposed to Cd (50 μg l −1) during 24 days, followed by a depuration period of six days. A battery of stress related biomarkers including antioxidant enzymes (superoxide dismutase–SOD, catalase–CAT; glutathione peroxidases–GPx), metallothioneins (MT), lipid peroxidation (LPO) and total oxyradical scavenging capacity (TOSC) were measured in the gills and mantle of B. azoricus. Cd was accumulated linearly during the exposure period in both tissues and no significant elimination occurred after the 6 days of depuration. Antioxidant enzymes activities were significantly higher in the gills. Cyt-SOD, T-GPx and Se-GPx were induced during the experiment but this was also observed in control organisms. Mit-SOD and CAT activities remained relatively unchanged. MT levels increased linearly in the gills of exposed mussels in the first 18 days of exposure. No significant differences were observed between LPO levels of control and exposed mussels. TOSC levels remained unchanged in control and exposed mussels. This suggests that although Cd is being accumulated in the tissues of exposed mussels, MT defence system is enough to detoxify the effect of Cd accumulated in the tissues. Furthermore, other factors besides the presence of Cd are influencing the antioxidant defence system in B. azoricus.

Concentrations and distributions of dissolved amino acids in fluids from Mid-Atlantic Ridge hydrothermal vents

The concentrations and distributions of dissolved free amino acids (DFAA) were determined in 31 hydrothermal fluid samples from the Logatchev field at 15°N and several hydrothermal vent fields between 4° and 9°S on the Mid-Atlantic ridge, sampled during three research cruises. The samples are derived from black smoker fluids with varying degrees of dilution, with end-member temperatures between 350 and 407°C, as well as of diffuse fluids with temperatures around 10°C. Most of the samples, even the hottest ones, contain significant amounts of DFAA and, with an average of 143 nM, more than in the deep water of the open ocean (below 50 nM, Lee and Bada, 1977). The highest values are found in diffuse fluids and the lowest in the hot fluids, but there are also some high-T fluids with high, as well as diffuse fluids with low concentrations. There are two larger groups of samples, distinguished by two different amino acid (AA) patterns: Group 1 has low concentrations in general, but relatively high concentrations of aspartic acid and glutamic acid, whereas group 2 has high abundances of aspartic acid, glutamic acid, serine, glycine, and alanine. The samples of the two groups do not share any other similarities, with the exception of their DFAA pattern. Thus, it appears that neither factor, such as fluid type or degree of dilution, influences the DFAA pattern, nor is the pattern site-specific. The presence of elevated AA concentrations in hydrothermal fluids implies that they are available as a nutrient source to vent organisms and as potential complexing agents for metals, possibly influencing their bioavailability and solubility.

Juvenile and adult scale worms Branchipolynoe seepensis in Lucky Strike hydrothermal vent mussels are genetically unrelated

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 3:79-87 (2008) - DOI: https://doi.org/10.3354/ab00060 Juvenile and adult scale worms Branchipolynoe seepensis in Lucky Strike hydrothermal vent mussels are genetically unrelated Sophie Plouviez1,2, Claire Daguin-Thiébaut1,2, Stéphane Hourdez1,2, Didier Jollivet1,2,* 1Université Pierre et Marie Curie-Paris 6, Laboratoire Adaptation et Diversité en Milieu Marin, Roscoff cedex, France 2CNRS, UMR7144 Station Biologique de Roscoff, BP 74, Place Georges Teissier, 29682, Roscoff cedex, France *Corresponding author. Email: jollivet@sb-roscoff.fr ABSTRACT: The deep-sea Mid-Atlantic Ridge hydrothermal vent mussel Bathymodiolus azoricus harbors the polynoid polychaete Branchipolynoe seepensis in its palleal cavity. The latter species possesses large, yolky oocytes (~400 µm) and has been hypothesized to brood its developing embryos. The present study used 6 microsatellite markers to assess kinship among adult and juvenile worms from the same host, among worms from mussels collected within a 1 m2 quadrat, and among samples taken on 2 dates (July 1998 and July 2001) at 2 sites (Tour Eiffel, TE, and Bairro Alto, BA) separated by 900 m at Lucky Strike hydrothermal vents on the Mid-Atlantic Ridge (37°16’ to 19’N, 32°15’ to 18’W). The hypothesis of genetic relatedness between females and juveniles within a single mussel, or among worms from the same quadrat was rejected. Conversely, great heterozygote deficiencies have been detected at nearly all loci, suggesting possible local inbreeding. There was no apparent genetic differentiation among worms from the 2 spatially separated quadrats collected at the TE and BA sites in 2001. These results suggest that embryonic or juvenile B. seepensis are released from their host mussel at a relatively early stage of development. They may settle close to the point of release or be dispersed to nearby sites or beyond. KEY WORDS: Adult/offspring kinship · Microsatellite · Dispersal · Polychaete · Mid-Atlantic Ridge Full text in pdf format PreviousNextCite this article as: Plouviez S, Daguin Thiébaut C, Hourdez S, Jollivet D (2008) Juvenile and adult scale worms Branchipolynoe seepensis in Lucky Strike hydrothermal vent mussels are genetically unrelated. Aquat Biol 3:79-87. https://doi.org/10.3354/ab00060 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 3, No. 1. Online publication date: July 17, 2008 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2008 Inter-Research.

New insigths on the metabolic diversity among the epibiotic microbial communitiy of the hydrothermal shrimp Rimicaris exoculata

The Rimicaris exoculata dominates the megafauna of some of the Mid Atlantic ridge hydrothermal vent sites. This species harbors a rich community of bacterial epibionts inside its gill chamber. Literature data indicate that a single 16S rRNA phylotype dominates this epibiotic community, and is assumed to be a sulfide–oxidizing bacteria. However attempts of cultivation were not successful and did not allow to confirm it. The aim of our study was to test the hypothesis of sulfide oxidation in the gill chamber, by a multidisciplinary approach, using in vivo experiments at in situ pressure in the presence of sulfide, microscopic observations and a molecular survey. Morphology of microorganisms, before and after treatment, was analyzed to test the effect of sulfide depletion and re-exposure. Our observations, as well as molecular data indicate a wider diversity than previously described for this shrimp's epibiotic community. We observed occurrence of bacterial intracellular sulfur– and iron–enriched granules and some methanotrophic–like bacteria cells for the first time. Genes that are characteristic of methane–oxidizing ( pmoA) and sulfide–oxidizing (APS) bacteria were identified. These results suggest that three metabolic types (iron, sulfide and methane oxidation) may co–occur within the epibiont community associated with Rimicaris exoculata. As this shrimp colonizes chemically contrasted environments, the relative abundance of each metabolic type could vary according to the local availability of reduced compounds.

Comparative petroleum hydrocarbons levels and biochemical responses in mussels from hydrothermal vents ( Bathymodiolus azoricus) and coastal environments ( Mytilus galloprovincialis)

Aliphatic hydrocarbons and PAHs in the whole soft tissues of Bathymodiolus azoricus from three Mid-Atlantic Ridge hydrothermal vents (Menez-Gwen, Lucky Strike and Rainbow), and Mytilus galloprovincialis from three contaminated coastal sites in South Portugal were analysed, and its effects on the digestive gland microsomes mixed-function oxygenase system (MFO) were assessed. Aliphatic hydrocarbons levels were present in the same magnitude in both coastal and hydrothermal environments, while the UCM (unresolved complex mixture) for coastal mussels were higher than in vent mussels. In general, significantly higher PAHs concentrations were found in coastal mussels, compared to B. azoricus where low molecular weight PAHs (2–3 rings) represented the majority of PAHs contrarily to what was observed in M. galloprovincialis. The MFO components were present in both mussel species, and were detected in vent mussels for the first time. However this system seems to have different roles in species from these contrasting environments. In coastal mussels MFO responded to hydrocarbon contamination while response in hydrothermal organisms appeared to be related mainly to endogenous factors.

Mercury concentrations in fish species caught at Mid-Atlantic Ridge hydrothermal vent fields

Concentrations of total mercury and methyl mercury were determined in muscle and liver samples of 8 fish species caught at the Menez Gwen, Lucky Strike and Rainbow hydrothermal vents (Mid-Atlantic Ridge). The species studied were Hydrolagus pallidus, H. affinis, Synapho- branchus kaupi, Epigonus telescopus, Mora moro, Antimora rostrata, Deania calceus and Etmopterus princeps. Median total mercury concentrations found in muscle tissue of the 8 species ranged between 0.6 and 1.9 µg g -1 wet weight and between 0.1 and 1.7 µg g -1 wet weight for liver tissue in 5 of the species. Differences in total mercury concentration in species caught at the different hydrothermal vents, comparisons between tissues and correlation with total length are described. In general, liver tissues present lower total mercury concentrations than muscle. Methyl mercury accu- mulated in fish from this study comprises, on average, >80% of the total mercury. The total mercury concentrations found were higher than those previously published for deep-sea fish. These fish spe- cies were exposed to high levels of mercury, due not only to bioavailability of toxic and stable forms of mercury in the water, but also to predation on organisms exposed to this metal.

Copepods of the family Dirivultidae (Siphonostomatoida) from deep-sea hydrothermal vent fields on the Mid-Atlantic Ridge at 14ºN and 5ºS

Five species of three genera of Dirivultidae Humes and Dojiri, 1980 were found at deep-sea hydrothermal vent fields on the Mid-Atlantic Ridge, at the Logachev-1 field at 14ºN and at two new sites (Turtle Pits and Red Lion) explored at 5ºS. The copepods were collected with a Remotely Operated Vehicle (ROV Quest 4000) and Video Controlled Grab, operated from the R/V Meteor during two cruises (M60/3 and M64/1) conducted in 2004 and 2005 at depths 2992–3048 m. The male of Stygiopontius lomonosovi n. sp. from the Logachev field shares a medioventrally prolonged syncoxa of the maxilliped with S. mirus Humes, 1996 and S. latulus Humes, 1996 from the Snake Pit at 23ºN of the Mid-Atlantic Ridge, but differs from them in having two, instead of three, outer spines on the distal exopodal segment of leg 4. Aphotopontius atlanteus Humes, 1996 previously known from the Lucky Strike and the Menez Gwen sites at 37°N and Rimipontius mediospinifer Humes, 1996 known from three sites (Logachev, Snake Pit, and Broken Spur at 29°N) are recorded from the Logachev field. Stygiopontius pectinatus Humes, 1987 previously recorded from the Mid-Atlantic Ridge hydrothermal vent fields TAG (26°N), Snake Pit, Broken Spur (29°N), and from the Mariana Back-Arc Basin of the Pacific Ocean and Stygiopontius cladarus Humes, 1996 previously known only from Snake Pit and Broken Spur, were found associated with alvinocaridid shrimps (Rimicaris sp.) from the hydrothermal vent field at 5ºS. The discovery of dirivultids at 5ºS represents the first record of copepods from a deep-sea hydrothermal vent southward of the Logachev field in the Atlantic Ocean.

Bioaccumulation of Hg, Cu, and Zn in the Azores triple junction hydrothermal vent fields food web

In this work, mercury (Hg), copper (Cu) and zinc (Zn) concentrations and tissue distribution are determined in seven benthic invertebrates species (the key species) from the Mid Atlantic Ridge (MAR) hydrothermal vent fields. The samples were collected from three hydrothermal vent fields – Menez Gwen, 840 m; Lucky Strike, 1700 m and Rainbow, 2300 m – near the Azores Triple Junction. These fields are characterized by different depths, geological context and chemical composition of the hydrothermal fluid, particularly the metal content, which is reflected by the metal concentrations in the organisms. Indeed, our results show that organisms from Menez Gwen presented the highest Hg concentrations, while those from Lucky Strike and Rainbow were richer in Cu and Zn. The potential transfer of these metals through two trophic links are also evaluated and include (1) the mussel Bathymodiolus azoricus and the commensal worm Branchipolynoe seepensis, and (2) three different species of shrimps and the crab Segonzacia mesatlantica. No evidence of Hg biomagnification in either of the vent food chains is clearly observed but an increase in Hg accumulation from prey to predator in the crustacean food chain. The same pattern was observed for Cu and Zn, even though these metals are not known to be generally biomagnified in food chains.

Antioxidant systems and lipid peroxidation in Bathymodiolus azoricus from Mid-Atlantic Ridge hydrothermal vent fields

Enzymatic defenses involved in protection from oxygen radical damage were determined in gills and mantle of Bathymodiolus azoricus collected from three contrasting Mid-Atlantic Ridge (MAR) hydrothermal vent fields (Menez-Gwen, Lucky Strike and Rainbow). The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) (total and Se-dependent), and levels of total oxyradical scavenging capacity (TOSC), metallothioneins (MT) and lipid peroxidation (LPO) were determined in B. azoricus tissues and the impact of metal concentrations on these antioxidant systems and lipid peroxidation assessed. SOD, CAT, TOSC, MTs and LPO levels were higher in B. azoricus gills while glutathione peroxidases (total and Se-dependent) were higher in the mantle, and with the exception of CAT, were of the same order of magnitude as in other molluscs. TOSC levels from Menez-Gwen indicate that the vent environment at this site is less stressful and the formation of ROS in mussels is effectively counteracted by the antioxidant defense system. TOSC depletion indicates an elevated ROS production in molluscs at the other two vent sites. Cytosolic SOD, GPx and LPO were more relevant at Lucky Strike (Bairro Alto) where levels of essential (Cu and Zn) and toxic metals (Cd and Ag) were highest in the organisms. CAT activity and LPO were predominant at the Rainbow vent site, where an excess of Fe in mussel tissues and in vent fluids (the highest of all three vent sites) may have contributed to increased LPO. Therefore, three distinct pathways for antioxidant enzyme systems and LPO based on environmental metal speciation of MAR vent fields are proposed for Bathymodiolus gills. At Menez-Gwen, TOSC towards peroxyl and hydroxyl radicals and peroxynitrite are predominant, while at Lucky Strike cytosolic SOD activity and GPx are the main antioxidant mechanisms. Finally at Rainbow, catalase and lipid peroxidation are dominant, suggesting that resistance of mussels to metal toxicity at these vent fields decreases in the sequence Menez-Gwen > Lucky Strike and Rainbow.

The effect of cadmium on antioxidant responses and the susceptibility to oxidative stress in the hydrothermal vent mussel Bathymodiolus azoricus

Hydrothermal vents are a unique environment of extreme physical–chemical characteristics and biological species composition. Cd is a toxic non-essential metal present in high concentrations in the hydrothermal vent environment, contrary to those found in marine coastal areas. Cd toxicity has been related, among other things, with reactive oxygen species production, even though this is a non-redox metal. Bathymodiolus azoricus is a deep-sea Mytilid bivalve very common in the Mid Atlantic Ridge (MAR) hydrothermal vent fields and very little is known about the antioxidant defence system in this specie. Because lethal Cd concentration in B. azoricus is unknown, the aim of this study was to assess the effects of a Cd concentration higher than that found in the hydrothermal vents on oxidative stress biomarkers, such as antioxidant enzymes. Mussels were exposed to 100 μg l−1 Cd during 24, 48 and 144 h, respectively, in a pressurized aquarium (IPOCAMP). Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), total oxyradical scavenging capacity (TOSC), metallothionein (MT) and lipid peroxidation (LPO) were measured in the gills and mantle of B. azoricus. The results indicate that gills are first affected by Cd toxicity. This may be due to different physiological functions of the tissues and by the presence of thio and methanotrophic symbiotic bacteria in the gills. The SOD and CAT are inhibited during the first day of exposure in the gills, although TOSC and MT concentrations were the same in control and exposed mussels. In the mantle, enzymatic activation only occurred after 6 days, and no significant differences in MT concentrations were found in the control and exposed mussels during the first day, as observed in the gills.

The ubiquitous mussel: Bathymodiolus aff. brevior symbiosis at the Central Indian Ridge hydrothermal vents

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 295:183-190 (2005) - doi:10.3354/meps295183 The ubiquitous mussel: Bathymodiolus aff. brevior symbiosis at the Central Indian Ridge hydrothermal vents Z. P. McKiness1,2, C. M. Cavanaugh1,* 1Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA2Present address: National Animal Disease Center, United States Department of Agriculture, Agricultural Research Service, 2300 Dayton Avenue, Ames, Iowa 50010, USA *Corresponding author. Email: cavanaug@fas.harvard.edu ABSTRACT: The discovery and exploration of hydrothermal vents on the Central Indian Ridge (CIR) yielded invaluable samples for further resolution of the biogeography of chemoautotrophic symbioses. Mytilid mussels were collected from 2 CIR hydrothermal vent fields and preliminary molecular analyses suggested phylogenetic affinity with the western Pacific vent mussel Bathymodiolus brevior. Resolving whether this mussel, designated B. aff. brevior, hosts a dual symbiosis, as characterized for the 2 Mid-Atlantic Ridge hydrothermal vent mussel species, or a single chemoautotrophic symbiosis, as seen in the Pacific vent mussel species, will provide insight into the evolutionary history of mytilid symbioses. Ultrastructural, physiological, and molecular evidence are reported herein which support the presence of a single endosymbiont phylotype with chemoautotrophic metabolism. Phylogenetic analyses placed this symbiont in the same clade as the vesicomyid clam symbionts, prompting discussion regarding the evolutionary origin of chemoautotrophic symbioses in vent bivalves. KEY WORDS: Chemoautotrophic endosymbiosis · Central Indian Ridge · Hydrothermal vent · Bathymodiolus spp. Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 295. Online publication date: June 23, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Thermosipho atlanticus sp. nov., a novel member of the Thermotogales isolated from a Mid-Atlantic Ridge hydrothermal vent

A novel anaerobic, thermophilic and heterotrophic bacterium, designated strain DV1140(T), was isolated from a deep-sea hydrothermal vent sample from the Mid-Atlantic Ridge. The cells were non-motile straight rods, 1.8 microm long and 0.4 microm wide, surrounded by an outer sheath-like structure (toga). They grew at 45-80 degrees C (optimum 65 degrees C), pH 5.0-9.0 (optimum pH 6.0) and at sea salt concentrations of 20-60 g l(-1) (optimum 30 g l(-1)). Strain DV1140(T) was able to ferment yeast extract, peptone, brain heart infusion, gelatin, starch, galactose, arabinose, glucose, trehalose and cellobiose. The fermentation products identified on glucose in the presence of yeast extract and peptone were acetate, isovalerate and hydrogen. The G+C content of the genomic DNA was 33 mol%. Phylogenetic analysis of the 16S rRNA gene sequence (GenBank accession number AJ577471) located the strain within the genus Thermosipho in the bacterial domain. On the basis of 16S rRNA gene sequence comparisons, and physiological and biochemical characteristics, the isolate represents a novel species, for which the name Thermosipho atlanticus sp. nov. is proposed. The type strain is DV1140(T) (=CIP 108053(T)=DSM 15807(T)).

TEM-EELS study of natural ferrihydrite from geological–biological interactions in hydrothermal systems

In this study, we have investigated the mineralogy present on the scaphognatite of the Rimicaris exoculata shrimp collected at a Mid-Atlantic Ridge hydrothermal vent. The structure, morphology and impurities of the minerals were analyzed by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The main minerals observed were clusters of iron oxides found attached to the bacterial cells present on the setae of the scaphognatite. Structural investigations based on high-resolution electron microscopy and electron diffraction affirm that these clusters are composed of two-line ferrihydrite. The EELS measurements demonstrate that the ferrihydrite is bearing a mixed valence iron distribution and P, Si, Ca, N and Ni ions at impurity levels. The stability of this uncommon phase is then discussed based on work previously reported in literature for analogous poorly ordered iron oxides.