Vent Mussel Research Articles

New fossil mussels (Bivalvia: Mytilidae) from Miocene hydrocarbon seep deposits, North Island, New Zealand, with general remarks on vent and seep mussels

New fossil mussels (Bivalvia: Mytilidae) from Miocene hydrocarbon seep deposits, North Island, New Zealand, with general remarks on vent and seep mussels

High-throughput sequencing and analysis of the gill tissue transcriptome from the deep-sea hydrothermal vent mussel Bathymodiolus azoricus

BackgroundBathymodiolus azoricus is a deep-sea hydrothermal vent mussel found in association with large faunal communities living in chemosynthetic environments at the bottom of the sea floor near the Azores Islands. Investigation of the exceptional physiological reactions that vent mussels have adopted in their habitat, including responses to environmental microbes, remains a difficult challenge for deep-sea biologists. In an attempt to reveal genes potentially involved in the deep-sea mussel innate immunity we carried out a high-throughput sequence analysis of freshly collected B. azoricus transcriptome using gills tissues as the primary source of immune transcripts given its strategic role in filtering the surrounding waterborne potentially infectious microorganisms. Additionally, a substantial EST data set was produced and from which a comprehensive collection of genes coding for putative proteins was organized in a dedicated database, "DeepSeaVent" the first deep-sea vent animal transcriptome database based on the 454 pyrosequencing technology.ResultsA normalized cDNA library from gills tissue was sequenced in a full 454 GS-FLX run, producing 778,996 sequencing reads. Assembly of the high quality reads resulted in 75,407 contigs of which 3,071 were singletons. A total of 39,425 transcripts were conceptually translated into amino-sequences of which 22,023 matched known proteins in the NCBI non-redundant protein database, 15,839 revealed conserved protein domains through InterPro functional classification and 9,584 were assigned with Gene Ontology terms. Queries conducted within the database enabled the identification of genes putatively involved in immune and inflammatory reactions which had not been previously evidenced in the vent mussel. Their physical counterpart was confirmed by semi-quantitative quantitative Reverse-Transcription-Polymerase Chain Reactions (RT-PCR) and their RNA transcription level by quantitative PCR (qPCR) experiments.ConclusionsWe have established the first tissue transcriptional analysis of a deep-sea hydrothermal vent animal and generated a searchable catalog of genes that provides a direct method of identifying and retrieving vast numbers of novel coding sequences which can be applied in gene expression profiling experiments from a non-conventional model organism. This provides the most comprehensive sequence resource for identifying novel genes currently available for a deep-sea vent organism, in particular, genes putatively involved in immune and inflammatory reactions in vent mussels.The characterization of the B. azoricus transcriptome will facilitate research into biological processes underlying physiological adaptations to hydrothermal vent environments and will provide a basis for expanding our understanding of genes putatively involved in adaptations processes during post-capture long term acclimatization experiments, at "sea-level" conditions, using B. azoricus as a model organism.

New fossil mussels (Bivalvia: Mytilidae) from Miocene hydrocarbon seep deposits, North Island, New Zealand, with general remarks on vent and seep mussels

Bathymodiolus (sensu lato) heretaunga sp. nov. and Gigantidas coseli sp. nov. are described from Miocene-age hydrocarbon seep carbonates of North Island, New Zealand, adding to only four described fossil hydrocarbon seep mussel species. Both new species are small compared to their modern congeners, and it is suggested that an evolutionary trend toward gigantism occurred in vent and seep mussels since the first known fossil species of the group appeared in the Middle Eocene. Bathymodiolus heretaunga is highly variable in morphology, potentially reflecting population variation over a wide geographic area. Gigantidas coseli is the first named species, fossil or modern, of its genus known from hydrocarbon seeps, although several closely related species in the same group, the Bathymodiolus childressi clade, have been reported from these environments.

Out of the deep sea into a land-based aquarium environment: investigating physiological adaptations in the hydrothermal vent mussel Bathymodiolus azoricus

AbstractBettencourt, R., Costa, V., Laranjo, M., Rosa, D., Pires, L., Colaço, A., Lopes, H., and Serrão Santos, R. 2011. Out of the deep sea into a land-based aquarium environment: investigating physiological adaptations in the hydrothermal vent mussel Bathymodiolus azoricus. – ICES Journal of Marine Science, 68: 357–364. Deep-sea hydrothermal vents are considered to be some of the most extreme environments in the world, yet the animals dwelling around the vent sites exhibit high productivity and must therefore deal with unusual levels of heavy metals, pH, temperature, CO2, and sulphides, in addition to environmental microbes. In an attempt to understand the physiological reactions of animals able to endure these extreme conditions, adaptation processes in the mussel Bathymodiolus azoricus maintained for long periods under laboratory conditions were investigated. Even in the absence of the characteristic high hydrostatic pressure found at deep-sea vent sites and without methane and/or sulphide supplementation, vent mussels seem to survive well in aquarium conditions. Therefore, the maintenance of live vent mussels in our laboratory is a key factor in gaining insights into their physiology, as well as into the study of evolutionary conserved molecules commonly found in other marine bivalves. With the aim of finding distinct genetic signatures in the expression of genes such as the metal-binding protein metallothionein (MT), the present work centred on cellular and humoral mechanisms in animals acclimatized to “sea-level” conditions. In addition, we also conducted experiments under hydrostatic pressure, using the hyperbaric chamber IPOCAMP to establish an in vitro experimental system in which the expression of genes that typically respond to heavy metal contaminants and oxidative stress could be studied under controlled hyperbaric pressure. We also analysed the occurrence of glycosylation in mantle and gill tissues from mussels subjected to elevated hyperbaric pressure, as well as the variation in haemocyte total counts as a result of increased pressure. Our results suggest that even after prolonged aquarium maintenance at atmospheric pressure, mussels were still able to induce the MT gene, whether or not they had been subjected to repressurization in the IPOCAMP chamber. Taken together, our results suggest that B. azoricus can be used as a model species and is particularly useful for the assessment of expression levels of critical genes, such as MT, in response to experimentally induced hydrostatic pressure.

LabHorta: a controlled aquarium system for monitoring physiological characteristics of the hydrothermal vent mussel Bathymodiolus azoricus

AbstractColaço, A., Bettencourt, R., Costa, V., Lino, S., Lopes, H., Martins, I., Pires, L., Prieto, C., and Serrão Santos, R. 2011. LabHorta: a controlled aquarium system for monitoring physiological characteristics of the hydrothermal vent mussel Bathymodiolus azoricus. – ICES Journal of Marine Science, 68: 349–356. LabHorta is a facility composed of laboratories and retrievable deep-sea cages created to support and expand the capabilities of research cruises. It also enhances the ability to conduct experimental studies with organisms from deep-sea hydrothermal vents and other deep-sea environments, while keeping them under controlled conditions of pressure and water chemistry. This paper presents a case study with the vent mussel Bathymodiolus azoricus (which harbours a dual symbiosis) collected at the Menez Gwen hydrothermal vent field at 840-m depth, transported to experimental aquaria at atmospheric pressure and maintained under four different controlled experimental conditions to study their comparative condition index (CI). Environmental parameters were monitored daily and efforts were made to keep these constant. During the first few months, there were differences between the CI scores of mussels kept under the various conditions. After 6 months, the differences are not so clear but mussels still had sulphur-oxidizing bacteria when fed with sulphide. The methane oxidizer bacteria disappear even in the presence of methane. A range of CI scores appeared as a function of the culture type. The LabHorta facility is a good tool for performing long-term physiological studies of deep-sea organisms, simulating possible changes in the natural environmental where they normally thrive.

The influence of nutritional conditions on metal uptake by the mixotrophic dual symbiosis harboring vent mussel Bathymodiolus azoricus

The vent mussel Bathymodiolus azoricus, host thioautotrophic and methanotrophic bacteria, in their gills and complementary, is able to digest suspended organic matter. But the involvement of nutritional status in metal uptake and storage remains unclear. The influence of B. azoricus physiological condition on its response to the exposure of a mixture of metals in solution is addressed. Mussels from the Menez Gwen field were exposed to 50 μg L − 1 Cd, plus 25 μg L − 1 Cu and 100 μg L − 1 Zn for 24 days. Four conditions were tested: (i) mussels harboring both bacteria but not feed, (ii) harboring only methanotrophic bacteria, (iii) without bacteria but fed during exposure and (iv) without bacteria during starvation. Unexposed mussels under the same conditions were used as controls. Eventual seasonal variations were assessed. Metal levels were quantified in subcellular fractions in gills and digestive gland. Metallothionein levels and condition indices were also quantified. Gill sections were used for fluorescence in situ hybridization (FISH) to assess the temporal distribution of symbiotic associations. Starvation damages metal homeostasis mechanisms and increase the intracellular Zn and MT levels function. There is a clear metallic competition for soluble and insoluble intracellular ligands at each condition. Seasonal variations were observed at metal uptake and storage.

Mixotrophy in the deep sea: a dual endosymbiotic hydrothermal mytilid assimilates dissolved and particulate organic matter

Bathymodiolus azoricus mussels thrive 840 to 2300 m deep at hydrothermal vents of the Azores Triple Junction on the Mid-Atlantic Ridge. Although previous studies have suggested a mixotrophic regime for this species, no analysis has yet yielded direct evidence for the assimilation of particulate material. In the present study, tracer experiments in aquaria with 13 C- and 15 N-labelled amino acids and marine cyanobacteria demonstrate for the first time the incorporation of dissolved and particulate organic matter in soft tissues of vent mussel. The observation of phytoplanktonic tests in wild mussel stomachs highlights the occurrence of in situ ingestion of sea-surface-derived mater- ial. Particulate organic carbon fluxes in sediment traps moored away from direct vent influence are in agreement with carbon export estimates from the surface ocean above the vents attenuated by microbial degradation. Stable isotope composition of trapped organic matter is similar to values pub- lished in the literature, but is enriched by +7‰ in 13 C and +13‰ in 15 N, relative to mussel gill tissue from the Menez Gwen vent. Although this observation suggests a negligible contribution of photo- synthetically produced organic matter to the diet of B. azoricus, the tracer experiments demonstrate that active suspension-feeding on particles and dissolved organic matter could contribute to the C and N budget of the mussel and should not be neglected.

Effect of long-term exposure to sulfides on taurine transporter gene expression in the gill of the deep-sea mussel Bathymodiolus platifrons, which harbors a methanotrophic symbiont

Seawater around deep-sea hydrothermal vents and cold seeps contain high levels of hydrogen sulfide, which is toxic to most animals. Invertebrates inhabiting these environments have been reported to accumulate high levels of thiotaurine, a sulfur-containing amino acid. Thiotaurine is likely to play an important role in sulfide detoxification, but its functions in the detoxification process are still unknown. We cloned methane-seep mussel Bathymodiolus platifrons cDNA encoding the taurine transporter (TAUT), which transports thiotaurine and its precursors across the cell membrane. Phylogenetic analyses revealed that the predicted peptide formed a clade with the TAUTs of shallow-water mussel Mytilus galloprovincialis and the hydrothermal vent mussel Bathymodiolus septemdierum that harbors thioautotrophic bacteria. We then reared B. platifrons in the presence or absence of Na2S and quantified TAUT mRNA using a real-time PCR system. The amount of TAUT mRNA in the gills of B. platifrons increased with rearing in the presence of Na2S for 69 days, but no change was observed in the absence of sulfide. These results suggest that TAUT plays an important role in sulfide detoxification, even in species that do not harbor thioautotrophic bacteria. The TAUT mRNA level was variable in the mantle and low in the foot throughout the entire rearing period, regardless of the presence/absence of sulfide, suggesting that TAUT gene expression is regulated differentially in each tissue.

Speciation in the Deep Sea: Multi-Locus Analysis of Divergence and Gene Flow between Two Hybridizing Species of Hydrothermal Vent Mussels

BackgroundReconstructing the history of divergence and gene flow between closely-related organisms has long been a difficult task of evolutionary genetics. Recently, new approaches based on the coalescence theory have been developed to test the existence of gene flow during the process of divergence. The deep sea is a motivating place to apply these new approaches. Differentiation by adaptation can be driven by the heterogeneity of the hydrothermal environment while populations should not have been strongly perturbed by climatic oscillations, the main cause of geographic isolation at the surface.Methodology/Principal FindingSamples of DNA sequences were obtained for seven nuclear loci and a mitochondrial locus in order to conduct a multi-locus analysis of divergence and gene flow between two closely related and hybridizing species of hydrothermal vent mussels, Bathymodiolus azoricus and B. puteoserpentis. The analysis revealed that (i) the two species have started to diverge approximately 0.760 million years ago, (ii) the B. azoricus population size was 2 to 5 time greater than the B. puteoserpentis and the ancestral population and (iii) gene flow between the two species occurred over the complete species range and was mainly asymmetric, at least for the chromosomal regions studied.Conclusions/SignificanceA long history of gene flow has been detected between the two Bathymodiolus species. However, it proved very difficult to conclusively distinguish secondary introgression from ongoing parapatric differentiation. As powerful as coalescence approaches could be, we are left by the fact that natural populations often deviates from standard assumptions of the underlying model. A more direct observation of the history of recombination at one of the seven loci studied suggests an initial period of allopatric differentiation during which recombination was blocked between lineages. Even in the deep sea, geographic isolation may well be a crucial promoter of speciation.

Relationship between the occurrence of filamentous bacteria on Bathymodiolus azoricus shell and the physiological and toxicological status of the vent mussel

The edifice walls of the Eiffel Tower hydrothermal vent site (Mid-Atlantic Ridge, Lucky Strike vent field) are populated with dense communities of dual symbioses harboring vent mussel Bathymodiolus azoricus, some of which are covered by white filamentous mats belonging to sulfur-oxidizing bacteria. Mussels were collected in both the presence and absence of the filamentous bacteria. A sample of the filamentous bacteria was collected and water measurements of temperature, CH 4 and H 2S were recorded at the collection area. The whole soft tissues were analyzed for total lipid, carbohydrate and total protein. Metallothioneins and metals (Cu, Fe and Zn) levels were determined in the major organs. The results showed no significant physiological and toxicological evidence that emphasizes the influence of associated sulfur-oxidizing filamentous bacteria on B. azoricus mussel shells. However, B. azoricus mussel seems to be well adapted to the assorted physico-chemical characteristics from the surrounding environment since it is able to manage the constant fluctuation of physico-chemical compounds.

Global depression in gene expression as a response to rapid thermal changes in vent mussels

Hydrothermal vent mussels belonging to the genus Bathymodiolus are distributed worldwide and dominate communities at shallow Atlantic hydrothermal sites. While organisms inhabiting coastal ecosystems are subjected to predictable oscillations of physical and chemical variables owing to tidal cycles, the vent mussels sustain pronounced temperature changes over short periods of time, correlated to the alternation of oxic/anoxic phases. In this context, we focused on the short-term adaptive response of mussels to temperature change at a molecular level. The mRNA expression of 23 genes involved in various cell functions of the vent mussel Bathymodiolus azoricus was followed after heat shocks for either 30 or 120 min, at 25 and 30 degrees C over a 48 h recovery period at 5 degrees C. Mussels were genotyped at 10 enzyme loci to explore a relationship between natural genetic variation, gene expression and temperature adaptation. Results indicate that the mussel response to increasing temperature is a depression in gene expression, such a response being genotypically correlated at least for the Pgm-1 locus. This suggests that an increase in temperature could be a signal triggering anaerobiosis for B. azoricus or this latter alternatively behaves more like a 'cold' stenotherm species, an attribute more related to its phylogenetic history, a cold seeps/wood fall origin.

Widespread occurrence of an intranuclear bacterial parasite in vent and seep bathymodiolin mussels

Many parasitic bacteria live in the cytoplasm of multicellular animals, but only a few are known to regularly invade their nuclei. In this study, we describe the novel bacterial parasite "Candidatus Endonucleobacter bathymodioli" that invades the nuclei of deep-sea bathymodiolin mussels from hydrothermal vents and cold seeps. Bathymodiolin mussels are well known for their symbiotic associations with sulfur- and methane-oxidizing bacteria. In contrast, the parasitic bacteria of vent and seep animals have received little attention despite their potential importance for deep-sea ecosystems. We first discovered the intranuclear parasite "Ca. E. bathymodioli" in Bathymodiolus puteoserpentis from the Logatchev hydrothermal vent field on the Mid-Atlantic Ridge. Using primers and probes specific to "Ca. E. bathymodioli" we found this intranuclear parasite in at least six other bathymodiolin species from vents and seeps around the world. Fluorescence in situ hybridization and transmission electron microscopy analyses of the developmental cycle of "Ca. E. bathymodioli" showed that the infection of a nucleus begins with a single rod-shaped bacterium which grows to an unseptated filament of up to 20 microm length and then divides repeatedly until the nucleus is filled with up to 80,000 bacteria. The greatly swollen nucleus destroys its host cell and the bacteria are released after the nuclear membrane bursts. Intriguingly, the only nuclei that were never infected by "Ca. E. bathymodioli" were those of the gill bacteriocytes. These cells contain the symbiotic sulfur- and methane-oxidizing bacteria, suggesting that the mussel symbionts can protect their host nuclei against the parasite. Phylogenetic analyses showed that the "Ca. E. bathymodioli" belongs to a monophyletic clade of Gammaproteobacteria associated with marine metazoans as diverse as sponges, corals, bivalves, gastropods, echinoderms, ascidians and fish. We hypothesize that many of the sequences from this clade originated from intranuclear bacteria, and that these are widespread in marine invertebrates.

Survival of mussels in extremely acidic waters on a submarine volcano

Increasing atmospheric carbon dioxide levels are causing ocean acidification, compromising the ability of some marine organisms to build and maintain support structures. An analysis of mussels from a submarine volcano setting with natural low-pH conditions shows low shell thicknesses and growth rates, but survival over up to four decades. Increasing atmospheric carbon dioxide levels are causing ocean acidification1,2, compromising the ability of some marine organisms to build and maintain support structures3 as the equilibrium state of inorganic carbon moves away from calcium carbonate4. Few marine organisms tolerate conditions where ocean pH falls significantly below today’s value of about 8.1 and aragonite and calcite saturation values below 1 (refs 5, 6). Here we report dense clusters of the vent mussel Bathymodiolus brevior in natural conditions of pH values between 5.36 and 7.29 on northwest Eifuku volcano, Mariana arc, where liquid carbon dioxide and hydrogen sulphide emerge in a hydrothermal setting. We find that both shell thickness and daily growth increments in shells from northwest Eifuku are only about half those recorded from mussels living in water with pH>7.8. Low pH may therefore also be implicated in metabolic impairment7. We identify four-decade-old mussels, but suggest that the mussels can survive for so long only if their protective shell covering remains intact: crabs that could expose the underlying calcium carbonate to dissolution are absent from this setting. The mussels’ ability to precipitate shells in such low-pH conditions is remarkable. Nevertheless, the vulnerability of molluscs to predators is likely to increase in a future ocean with low pH.

Mantle-to-shell CaCO3 transfer during shell repair at different hydrostatic pressures in the deep-sea vent mussel Bathymodiolus azoricus (Bivalvia: Mytilidae)

Calcium carbonate transfer was experimentally examined in hydrothermal mussels Bathymodiolus azoricus, which were collected from 850 m depth at Menez Gwen hydrothermal vent site (31°31′W, 37°50′N) on the Mid Atlantic Ridge in May 2007. In each of four 10-day experiments, groups of mussels were maintained at atmospheric pressure or re-pressurised to depths relevant to their site of occurrence, i.e. 850 m depth at Menez Gwen, 1,750 m at Lucky Strike (31°31′W, 37°18′N) and 2,300 m at Rainbow (31°31′W, 36°13′N). The shells of experimental mussels were perforated and mantle tissue was fixed for light and TEM studies at days 7 and 10 following the injury. Simultaneously, haemocytes from the extrapallial fluid (EPF) at the site of induction were studied. At day 7 the response was most intense in the middle fold of the mantle margin and possibly proportional to hydrostatic pressure. At day 10 the epithelial cells on the mantle surface facing the body cavity produced copious organic secretions that avidly bound calcium. Haemocyte migration was noted within the mantle tissue, and the haemocytes at the mantle surface facing the shell had a Ca-positive granular content. Large haemocytes were detected in the EPF at the injury site, and some showed evidence of an immune reaction while others showed Ca-positive granular content. These results suggest that haemocytes are involved in shell repair in these deep-sea mussels just as in some freshwater and shallow marine molluscs.

Innate immunity in the deep sea hydrothermal vent mussel Bathymodiolus azoricus

The interaction between microorganisms and host defense mechanisms is a decisive factor for the survival of marine bivalves. They rely on cell-mediated and humoral reactions to overcome the pathogens that naturally occur in the marine environment. In order to understand host defense reactions in animals inhabiting extreme environments we investigated some of the components from the immune system of the deep sea hydrothermal vent mussel Bathymodiolus azoricus. Cellular constituents in the hemolymph and extrapallial fluid were examined and led to the identification of three types of hemocytes revealing the granulocytes as the most abundant type of cell. To further characterize hemocyte types, the presence of cell surface carbohydrate epitopes was demonstrated with fluorescent WGA lectin, which was mostly ascribed to the granulocytes. Cellular reactions were then investigated by means of phagocytosis and by the activation of putative MAPKs using the microbial compounds zymosan, glucan, peptidoglycan and lipopolysaccharide. Two bacterial agents, Bacillus subtilis and Vibrio parahaemolyticus, were also used to stimulate hemocytes. The results showed that granulocytes were the main phagocytic cells in both hemolymph and extrapallial fluid of B. azoricus. Western blotting analyses using commercially available antibodies against ERK, p38 and JNK, suggested that these putative kinases are involved in signal transduction pathways during experimental stimulation of B. azoricus hemocytes. The fluorescent Ca 2+ indicator Fura-2 AM was also insightful in demonstrating hemocyte stimulation in the presence of laminarin or live V. parahaemolyticus. Finally, the expression of the antibacterial gene mytilin was analyzed in gill tissues by means of RT-PCR and whole-mount in situ hybridization. Mytilin transcripts were localized in hemocytes underlying gill epithelium. Moreover, mytilin was induced by exposure of live animals to V. parahaemolyticus. These findings support the premise of a conserved innate immune system in B. azoricus. Such system is comparable to other Bivalves and involves the participation of cellular and humoral components.

Transcriptomic approach to study the response to rapid changes of temperature in the hydrothermal vent mussel Bathymodiolus azoricus

Transcriptomic approach to study the response to rapid changes of temperature in the hydrothermal vent mussel Bathymodiolus azoricus

Characterisation of genes involved in symbiosis between hydrothermal vent mussel Bathymodiolus azoricus and methanotrophic and sulfoxydant bacteria

Characterisation of genes involved in symbiosis between hydrothermal vent mussel Bathymodiolus azoricus and methanotrophic and sulfoxydant bacteria

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.

Haemocyte response associated with induction of shell regeneration in the deep-sea vent mussel Bathymodiolus azoricus (Bivalvia: Mytilidae)

This study reports on the haemocyte responses after induction of shell regeneration in the hydrothermal mussel Bathymodiolus azoricus. Haemolymph was drawn from live mussels collected at Menez Gwen hydrothermal vent site (850 m depth) at the Mid Atlantic Ridge (MAR) and was compared with those collected following laboratory acclimatisation (1 atm and Ca-rich algal diet) and also with induced specimen for up to 30 days. Simultaneously, histological changes in mantle micro-morphology with the histochemical detection of Ca mobilisation in tissues were conducted. On the basis of light- and transmission electron microscopy, it is concluded that the physiological equipment involved in shell regeneration in the deep sea bivalve closely resembles that in littoral mytilids, a group that B. azoricus is closely related. This in spite of previously alleged molecular and cellular adaptations to extreme conditions typical at deep sea hydrothermal vents. Three types of blood cells were identified sharing various morphological similarities with those in many non-vent bivalves. Significant increase in the number of circulating haemocytes was detected from day 5 after induction shell regeneration. It is suggested that the increase may be a result of migration of haemocytes from the connective tissue, probably to the shell growth frontline. It is alleged that a first peak in haemocyte number is a non-specific immune response related wound healing, which renders changes in the pallial fluid that are favourable for CaCO 3 deposition. The conspicuous presence of an unidentified, acid soluble, highly refractive structure in the haemolymph of induced mussels was detected, which may play a role in Ca nucleation. This study has set the stage for investigations underway on the influence of hydrostatic pressure on shell biomineralisation in B. azoricus subjected to post-capture hyperbaric simulations.

Changes of gill and hemocyte-related bio-indicators during long term maintenance of the vent mussel Bathymodiolus azoricus held in aquaria at atmospheric pressure

The deep-sea hydrothermal vent mussel Bathymodiolus azoricus has been the subject of several studies aimed at understanding the physiological adaptations that vent animals have developed in order to cope with the particular physical and chemical conditions of hydrothermal environments. In spite of reports describing successful procedures to maintain vent mussels under laboratory conditions at atmospheric pressure, few studies have described the mussel's physiological state after a long period in aquaria. In the present study, we investigate changes in mucocytes and hemocytes in B. azoricus over the course of several months after deep-sea retrieval. The visualization of granules of mucopolysaccharide or glycoprotein was made possible through their inherent auto-fluorescent property and the Alcian blue-Periodic Acid Schiff staining method. The density and distribution of droplets of mucus-like granules was observed at the ventral end of lamellae during acclimatization period. The mucus-like granules were greatly reduced after 3 months and nearly absent after 6 months of aquarium conditions. Additionally, we examined the depletion of endosymbiont bacteria from gill tissues, which typically occurs within a few weeks in sea water under laboratory conditions. The physiological state of B. azoricus after 6 months of acclimatization was also examined by means of phagocytosis assays using hemocytes. Hemocytes from mussels held in aquaria up to 6 months were still capable of phagocytosis but to a lesser extent when compared to the number of ingested yeast particles per phagocytic hemocytes from freshly collected vent mussels. We suggest that the changes in gill mucopolysaccharides and hemocyte glycoproteins, the endosymbiont abundance in gill tissues and phagocytosis are useful health criteria to assess long term maintenance of B. azoricus in aquaria. Furthermore, the laboratory set up to which vent mussels were acclimatized is an applicable system to study physiological reactions such as hemocyte immunocompetence even in the absence of the high hydrostatic pressure found at deep-sea vent sites.