Extrait de : Histoire des plantes de la Guiane Françoise, rangées suivant la méthode sexuelle, avec plusieurs mémoires sur différens objets intéreffans, relatifs à la culture & au commerce de la Guiane Françoife, & une notice des plantes de l'Ifle-de-France, Tome Troisième (Planche 155)
Siècle(s) traité(s) : 18
Droits : Domaine public
Permalien : http://www.manioc.org/images/FRA110560319i1
FRA110560319i1

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria which ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, East America, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous more easily accessible shallow marine species were studied. We here provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to Marmara Sea, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 51 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae), and compared among families with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions, yet relatively little is known regarding their diversity and functioning apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on Oceans, we advocate for a better assessment of bivalve symbioses diversity in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change
Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2013 , Vol. 10 , N. 5 , P. 3241-3267

Droits : Author(s) 2012. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00133/24417/22431.pdf
DOI:10.5194/bg-10-3241-2013
http://archimer.ifremer.fr/doc/00133/24417/

Résumé : Shelled molluscs are comprised of bivalves and gastropods. They are settled mainly on the continental shelf as benthic and sedentary animals due to their heavy protective shell. They can stand a wide range of environmental conditions. They are found in the whole trophic chain and are particle feeders, herbivorous, carnivorous, and predators. Exploited mollusc species are numerous. The main groups of gastropods are the whelks, conchs, abalones, tops, and turbans; and those of bivalve species are oysters, mussels, scallops, and clams. They are mainly used for food, but also for ornamental purposes, in shellcraft industries and jewelery. Consumed species are produced by fisheries and aquaculture, the latter representing 75% of the total 11.4 millions metric tons landed worldwide in 1996. Aquaculture, which mainly concerns bivalves (oysters, scallops, and mussels) relies on the simple techniques of producing juveniles, natural spat collection, and hatchery, and the fact that many species are planktivores.
Fisheries and aquaculture. Encyclopedia of life support systems : Volume II ; edited by Patrick Safran

Droits : Encyclopedia of Life Support Systems (EOLSS)
http://archimer.ifremer.fr/doc/2001/publication-529.pdf
http://archimer.ifremer.fr/doc/00000/529/

Résumé : Arbol de hasta 18 m de alto. Hojas pecioladas, subcoriáceas, oblongo elípticas a lanceoladas, agudamente acuminadas, pinnado nervadas de hasta 13 cm de longitud. Inflorescencias estaminadas de 3 a 20 flores; las pistiladas usualmente de una sola flor; flores pequeñas, amarillo cremosas. Fruto piriforme o subgloboso (nuez) de hasta 5 cm, colgante, rojizo o amarillento, con dos valvas; semilla con arilo escarlata.
Arbre pouvant atteindre 18 m de haut. Feuilles pétiolées, presque coriaces, oblongo-elliptiques à lancéolées, terminées en pointe très fine, pennatinnervées pouvant atteindre 13 cm de long. Inflorescences staminées de 3 à 20 fleurs; celles qui sont pourvues d’un pistil ont habituellement une seule fleur; fleurs petites, jaunes-crèmes. Fruit piriforme ou presque arrondi pouvant atteindre 5 cm, tombant, rougeâtre ou jaunâtre, bivalve; graine avec arille écarlate.
Tree dioecious 6-18 m high with a dense crown and aromatic wood.  Leaves simple, alternate, oblong-elliptic, acutely acuminate, pinnately veined, dark green shiny above, paler beneath, 5-15 cm x 2-7 cm; male inflorescences usually 1-10 flowered cyme, fragrant, pale yellow, female inflorescences a 1-3 flowered cyme, but usually 1-flowered, pale yellow; fruit a fleshy, smooth, yellow, sub-globose, drupe, 3-6 cm long with a circumferential, longitudinal ridge; seed brown, ovoid 1.5-4.5cm long covered with a lacinate, red aril.
Nativa de Asia tropical, cultivada en los trópicos del resto del mundo.
Originaire d’;Asie tropicale, cultivée dans les tropiques du reste du monde.
Native to tropical Asia, cultivated in tropical regions around the world.

http://www.tramil.net/fototeca/plant239

Éditeur(s) : Elsevier
Résumé : The gametogenic cycle and the reproductive effort of the blacklip pearl oyster, Pinctada margaritifera, cultivated in Takapoto lagoon were studied for a 1-year period (March 1997-April 1998) by bimonthly observations of gonadal sections, dry tissue weights and gonadal index in a population of pearl oyster composed of three age-groups. pearl oysters attained sexual maturity in the end of their first year (height approximate to 40 mm), implying that P. margaritifera is a late-maturing species in comparison with other Pteriidae. This species was also confirmed to be a marked protandrous successive hermaphrodite in culture, with 100 % of males at first maturity and 75 % in older pearl oyster (height > 120 mm). The general pattern of gametogenic activity, fairly synchronous in both sexes, was comparable with that of other tropical bivalves: reproduction occurs continuously throughout the year with a maximal activity during the warm season (November-May). No resting period was observed. Quantitative growth data showed that P. margaritifera exhibits an annual synchronised polymodal spawning pattern, with two spawning peaks in age-group I (height approximate to 70 mm) and five in age-groups II (height approximate to 100 mm) and III (height approximate to 120 mm). Spawning was sometimes incomplete, nevertheless a clear relationship between gamete production (P-R, g) and size (height H, mm) was obtained: P-R = 5.26 x 10(-7) H-2.91 (R-2 = 0.99, p < 0.05). Estimation of P-R was used to calculate the annual reproductive effort in P. margaritifera. Reproductive effort (%) was similar to those calculated for temperate species and showed a progressive increase with the age of pearl oyster, from 7 % in age-group I to 38 % in age-group III. This study showed that, in a fairly stable tropical environment such as the Takapoto lagoon, P. margaritifera is a multiple spawner, which uses an opportunistic reproductive strategy, allowing investment all year around, of any surplus energy into gamete production. Surplus energy is ensured by the high pumping rates developed by this non-symbiotic bivalve to succeed in low seston conditions. (C) 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medicales Elsevier SAS.
Le cycle et l'effort de reproduction de l'huître perlière à lèvres noires, Pinctada margaritifera, cultivée dans le lagon de Takapoto, ont été étudiés sur une période annuelle (de mars 1997 à avril 1998), par un suivi bimensuel des stades de maturation et des indices gonadiques, sur une population en élevage composée de trois groupes d'âge (1, 2 et 3 ans). Cette étude a confirmé que P. margaritifera est une espèce qui se reproduit tardivement par rapport aux autres Ptériidés (elle atteint sa maturité sexuelle à la fin de sa première année, pour une hauteur approximative de 40 mm). Par ailleurs, elle présente, en élevage, une protandrie marquée (100 % de mâles à première maturité, 75 % pour des huîtres âgées de trois ans). Le schéma général de sa gamétogenèse, relativement synchrone dans les deux sexes, est comparable à celui des autres bivalves tropicaux : la reproduction est quasiment continue (aucune période de repos sexuel) avec une activité accrue en saison chaude (de novembre à mai). L'analyse des variations du poids de la gonade suggère l'existence de deux pics d'émission de gamètes chez les huîtres de un an et cinq pics chez les huîtres de 2 et 3 ans (cycle de reproduction de type polymodal). Bien que ces émissions de gamètes soient parfois incomplètes, une relation entre la production de gamètes (PR, en g) et la taille de l'huître perlière (hauteur, H, en mm) a été établie : PR = 5,26 x 10-7 H2,91 (R2 = 0,99, p < 0,05). Ces résultats ont permis de calculer l'effort de reproduction de P. margaritifera à Takapoto et sur un bilan annuel : il augmente avec l'âge de l'huître perlière de 7 % pour le groupe d'âge I à 38% pour le groupe d'âge III. Ces valeurs annuelles sont similaires à celles calculées chez les bivalves de milieux tempérés. Cette étude a donc montré que, dans un environnement tropical assez stable tel que celui du lagon de Takapoto, P. margaritifera présente une reproduction continue, avec plusieurs pics d'émission de gamètes par an. Cette stratégie « opportuniste » permet l'investissement, de tout surplus d'énergie en production de gamètes, tout au long de l'année. Malgré la faible concentration du milieu en nourriture, ces surplus d'énergie sont assurés par les fortes capacités de filtration développées par cette espèce tropicale non-symbiotique.
Aquatic Living Resources (0990-7440) (Elsevier), 2000 , Vol. 13 , N. 1 , P. 37-48

Droits : 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Éditions scientifiques et médicales Elsevier SAS
http://archimer.ifremer.fr/doc/2000/publication-1391.pdf
DOI:10.1016/S0990-7440(00)00135-2
http://archimer.ifremer.fr/doc/00000/1391/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
In this study, the cellular organization of the gill that harbors symbiotic bacteria is described in the thyasirid Thyasira falklandica collected from South Shetlands in Antarctic. Sections of the gills revealed that T. falklandica belongs to the gill type 3, as described by Dufour (Biol Bull, 208:200-212, 2005), with an elongated lateral zone along the frontal-abfrontal axis of the gill Wlaments. The ciliated and intermediary zones looked similar to those described in symbionts-bearing bivalves. The lateral zone is more complex in T. falklandica than in other Thyasiridae already described. Such a zone is composed of four different cell types. Bacteriocytes are abundant in the frontal and abfrontal positions, while the middle part of the lateral zone is occupied mostly by numerous granule cells devoid of bacteria. All along the lateral zone, TEM and SEM observations show some ciliated cells, which are regularly interspersed between bacteriocytes and/or granule cells. Such cells, according to the long double ciliary roots of their cilia, should have a sensory function. Intercalary cells, which have never been observed between bacteriocytes, are restricted to the middle part of the lateral zone where their expansions overlap the adjacent granule cells. Bacterial symbionts occur only extracellularly among long microvilli diVerentiated by the bacteriocytes. They are abundant, usually spherical in shape (around 0.7 m length), and covered by the glycocalix from bacteriocyte microvilli. According to TEM views, the empty vesicles located in the periplasmic space should be sulfur storage, as known for other sulfur-oxidizing symbionts.
ISSN: 0720-213X

hal-00755289
https://hal.univ-antilles.fr/hal-00755289
DOI : 10.1007/s00435-007-0034-4

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The mangrove swamp environment constitutes a sulphide rich habitat harbouring some thioautotrophic organisms. The ciliate Zoothamnium niveum and the nematode Eubostrichus dianae, both known to live associated with bacterial sulphide-oxidizing ectosymbionts, were analysed as positive controls by Raman microspectrometry. The detection of the 3 Raman bands characteristic of elemental sulphur (S8) allows us to define a positive model of sulphide-oxidizing symbiotic invertebrates and by extrapolation, of thioautotrophic organisms. A fast screening using this tool was carried out on eukaryotic organisms such as hydrozoan, nematodes, annelids, copepods, and ciliate (Pseudovorticella sp.) and on free-living filamentous bacteria found on decomposing leaves in order to detect thioautotrophic organisms. The Raman microspectrometry permits us: (i) to reveal thioautotrophic metabolism of free-living bacteria (Beggiatoa sp.) and even for Archaea and (ii) to detect sulphide-oxidizing endosymbiotic and ectosymbiotic bacteria associated with the Bivalve Lucina pectinata and Pseudovorticella sp., respectively. Raman microspectrometry represents a fast, easy and non destructive technique which can be used on living organisms without constraints of sample size. The Raman analysis can also be completed by ultrastructural analysis (SEM, TEM) on the same sample.
ISSN: 0141-1136

hal-00715329
https://hal.univ-antilles.fr/hal-00715329
DOI : 10.1016/j.marenvres.2010.02.001

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : International audience
Cyanobacterial toxins and pesticides regularly impact freshwaters. Microcystin-LR is one of the most toxic and common cyanobacterial toxins whereas glyphosate is the active ingredient of a widely use herbicide. As filter feeders, freshwater mussels are particularly exposed. Like many native bivalve species, Unio pictorum suffers from a continuous decline in Europe. In order to get a deeper insight of its response to contaminants, U. pictorum was exposed to either 10 μg L(-1) of microcystin-LR or 10 μg L(-1) of glyphosate or a mixture of both. Proteins of the digestive glands were extracted and analyzed by DIGE. Gel analysis revealed 103 spots with statistical variations, and the response seems to be less toward glyphosate than to microcystin-LR. Specific spots have variations only when exposed to the mixture, showing that there is an interaction of both contaminants in the responses triggered. The proteins of 30 spots have been identified. They belong mostly to the cytoskeleton family, but proteins of the oxidative pathway, detoxification, and energetic metabolism were affected either by glyphosate or microcystin-LR or by the mixture. These results demonstrate the importance to study contaminants at low concentrations representative of those found in the field and that multicontaminations can lead to different response pathways.
ISSN: 1535-3893

hal-00877711
https://hal.archives-ouvertes.fr/hal-00877711
DOI : 10.1021/pr4006316
PUBMED : 23972258

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
The shallow water bivalve Codakia orbicularis lives in symbiotic association with a sulfur-oxidizing bacterium in its gills. The endosymbiont fixes CO2 and thus generates organic carbon compounds, which support the host's growth. To investigate the uncultured symbiont's metabolism and symbiont-host interactions in detail we conducted a proteogenomic analysis of purified bacteria. Unexpectedly, our results reveal a hitherto completely unrecognized feature of the C. orbicularis symbiont's physiology: the symbiont's genome encodes all proteins necessary for biological nitrogen fixation (diazotrophy). Expression of the respective genes under standard ambient conditions was confirmed by proteomics. Nitrogenase activity in the symbiont was also verified by enzyme activity assays. Phylogenetic analysis of the bacterial nitrogenase reductase NifH revealed the symbiont's close relationship to free-living nitrogen-fixing Proteobacteria from the seagrass sediment. The C. orbicularis symbiont, here tentatively named `Candidatus Thiodiazotropha endolucinida', may thus not only sustain the bivalve's carbon demands. C. orbicularis may also benefit from a steady supply of fixed nitrogen from its symbiont-a scenario that is unprecedented in comparable chemoautotrophic symbioses.
ISSN: 2058-5276

hal-01545904
https://hal.archives-ouvertes.fr/hal-01545904
DOI : 10.1038/nmicrobiol.2016.193

Éditeur(s) : Inter-research
Résumé : Environmental conditions experienced by aquatic organisms are archived in biogenic carbonates such as fish otoliths, bivalve shells and coral skeletons. These calcified structures present an accretionary growth and variations in optical properties - color or opacity - that are used to reconstruct time. Full and reliable exploitation of the information extracted from these structures is, however, often limited as the metabolic processes that control their growth and their optical properties are poorly understood. Here, we propose a new modeling framework that couples both the growth of a biogenic carbonate and its optical properties with the metabolism of the organism. The model relies on well-tested properties of Dynamic Energy Budget (DEB) theory. It is applied to otoliths of the Bay of Biscay anchovy (Engraulis encrasicolus) for which a DEB model has been previously developed. The model reproduces well-known otolith patterns and thus provides us with mechanisms for the metabolic control of otolith size and opacity at the scale of an individual lifespan. Two original contributions using this framework are demonstrated. First, the model can be used to reconstruct the temporal variations in the food assimilated by an individual fish. Reconstructing food conditions of past and present aquatic species in their natural environment is key ecological information to better understand population dynamics. Second, we show that non-seasonal checks can be discriminated from seasonal checks, which is a well-recognized problem when interpreting fish otoliths. We discuss further developments of the model and the experimental settings required to test this new promising framework.
Marine Ecology-progress Series (0171-8630) (Inter-research), 2012 , Vol. 447 , P. 151-164

Droits : 2012 Inter-Research
http://archimer.ifremer.fr/doc/00060/17082/14593.pdf
DOI:10.3354/meps09492
http://archimer.ifremer.fr/doc/00060/17082/

Éditeur(s) : Natl Shellfisheries Assoc
Résumé : The pearl industry in French Polynesia is based on exploitation of natural stocks of the black-lip pearl oyster (Pinctada margaritifera); it generates an annual turnover of 90 million euros. Improvements in pearl quality need genetic studies to improve the populations. This pearl oyster is a protandric species, where the sex-ratio normally is biased towards males. There is an increasing interest in gender control to find the mechanisms to augment female proportions for management purposes. This review summarizes information on exogenous and endogenous factors regulating gender in this and other bivalves and concludes that P. margaritifera is a protandric hermaphrodite, developing as a male during the first two years and without evidence of an effect from abiotic and biotic factors on gender during this phase. Later, pearl oysters progressively change to females, reaching a sex ratio close to 1:1 in specimens >8 years; at this stage, gender is apparently influenced by environmental parameters, but particularly by stress. Future research should seek to accurately determine the effect of temperature and food on sex ratios. Studies should be performed to characterize genes responsible for expression of gender. The use of hormones is a path that might be explored to influence the gender of pearl oysters.
Journal Of Shellfish Research (0730-8000) (Natl Shellfisheries Assoc), 2011-08 , Vol. 30 , N. 2 , P. 231-240

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00040/15100/12543.pdf
DOI:10.2983/035.030.0206
http://archimer.ifremer.fr/doc/00040/15100/

Éditeur(s) : Elsevier Science Bv
Résumé : In bivalve aquaculture, dominant fouling organisms are filter feeders which can compete for food with reared bivalves, sometimes causing mortality or reducing their growth rate. This study investigated the effect of biofouling on the farmed pearl oyster Pinctada margaritifera in two lagoons of French Polynesia. Survival, growth and reproduction of 2 year-old pearl oysters were monitored with regular sampling schedules, from the initial stage of colonization up to 20 months of biofouling accumulation. Control groups of pearl oysters were kept free of biofouling as is the current practice in pearl farms. After more than a year of monitoring, no significant difference was recorded in shell growth rate between pearl oysters reared with epibionts and the control group of pearl oysters, at both sites. Mean annual shell growth rate (height) was 30.5 ± 9.2 mm in Tahiti and 24.8 ± 7.7 mm in Mangareva. Neither the survival nor the reproduction indices were negatively affected by biofouling. In Mangareva, where biofouling development was quantified during 1 year, the rate of colonization appeared to be high during the first 3 months before slowing down. These results raise questions about the necessity of removing biofouling at this stage of pearl oyster production (i.e. before grafting).
Aquaculture (0044-8486) (Elsevier Science Bv), 2014-10 , Vol. 434 , P. 18-26

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00201/31188/29587.pdf
DOI:10.1016/j.aquaculture.2014.07.012
http://archimer.ifremer.fr/doc/00201/31188/

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Associations between marine invertebrates and chemoautotrophic bacteria constitute a wide field for the study of symbiotic associations. In these interactions, symbiont transmission must represent the cornerstone allowing the persistence of the association throughout generations. Within Bivalvia, in families such as Solemyidae or Vesicomyidae, symbiont transmission is undoubtedly vertical. However, in Lucinidae, symbiont transmission is described in the literature as 'environmental', symbionts being acquired from the environment by the new host generations. Hence, if there is transmission, symbionts should be transmitted from adults to juveniles via the environment. Consequently, we should observe a release of the symbiont by adults. We attempted to detect such a release within two Lucinidae species of the genus Codakia. We sampled 10 Codakia orbicularis and 20 Codakia orbiculata distributed in 10 crystallizing dishes containing filtered seawater. During 1 month of investigation, we analyzed water of the dishes in order to detect any release of a symbiont using catalyzed report deposition-FISH techniques. For 140 observations realized during this period, we did not observe any release of symbionts. This suggests that the idea of host-to-host passage in Lucinidae is inaccurate. We could therefore consider that the transmission mode from generation to generation does not occur within Lucinidae, symbiosis appearing to be advantageous in this case only for the host, and constitutes an evolutionary dead-end for the bacteria.
ISSN: 0168-6496

hal-00751560
https://hal.univ-antilles.fr/hal-00751560
DOI : 10.1111/j.1574-6941.2008.00626.x

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The Caribbean bivalves Codakia orbicularis (Linnée, 1758) and C. orbiculata (Montagu, 1808) live in seagrass beds of Thalassia testudinum and harbor intracellular sulfuroxidizing gamma-proteobacteria. These bacterial symbionts fix CO2 via the Calvin Benson cycle and provide organic compounds to the bivalve. During experimentally induced starvation, no reduced sulfur compounds and no organic particle food are available; the symbionts could be considered as the sole nutrient source of the host bivalve. A previous study has shown that the intracellular bacterial population decreased considerably during starvation and that bacterial endosymbionts were not released by the bivalves. In this study, the activity of two lysosomal marker enzymes (acid phosphatase and arylsulfatase) was detected using cytochemical experiments coupled with energy-dispersive X-ray transmission electron microscopy during sulfide and organic particle starvation. The degradation of bacterial endosymbionts began after 2 weeks of starvation in C. orbiculata and after 3 weeks in C. orbicularis. Degradation processes seem to be continuous over several months and could be responsible for the disappearance of the bacterial endosymbionts within the gills during starvation. These data suggest that the host use symbionts as a nutrient source to survive a hunger crisis. The carbon transfer from the symbionts to the host could be flexible and could consist in transfer of organic matter, “milking,” under normal feeding conditions and digestion of the symbionts under starved conditions.
ISSN: 1059-910X

Droits : info:eu-repo/semantics/OpenAccess
hal-01206367
https://hal.univ-antilles.fr/hal-01206367
https://hal.univ-antilles.fr/hal-01206367/document
https://hal.univ-antilles.fr/hal-01206367/file/revised%20version%20to%20be%20submitted%20to%20the%20editor3oct.pdf
DOI : 10.1002/jemt.22458

Éditeur(s) : Gauthier-villars
Résumé : 70 hydrothermal sites were observed during the 23 dives of the French submersible Nautile (''Naudur'' cruise, December 1993), at 17-degrees-19-degrees-S on the East Pacific Rise. Large vent-animal communities are present around these sites. The zoological composition of these communities is the same as that of the communities at 11-degrees-13-degrees-N and 21-degrees-N on the East Pacific Rise. However, the distribution of the species on the sites is different from all the other hydrothermal communities; large anemone fields of several hundred square metres, associated with colonies of Bathymodiolus and Calyptogena, have been observed. Fresh lava areas seem to bear the most important biological activity.
70 sites hydrothermaux actifs ont été découverts lors des 23 plongées du submersible français Nautile (campagne « Naudur », décembre 1993) sur la dorsale Est Pacifique, entre 17°S et 19°S. D'importantes communautés animales leur sont associées, et bien que les animaux qui les constituent soient analogues à ceux observés sur cette même dorsale à 1 r-13°N et 21°N, les structures des peuplements sont différentes de celles connues par ailleurs. Des champs d'anémones et de bivalves (Bathymodiolus et Calyptogena) de plusieurs centaines de mètres carrés ont été observés (17°25'S). Les zones de laves les plus récentes paraissent les plus riches biologiquement
Comptes Rendus de l'Academie des Sciences Serie II (1251-8069) (Gauthier-villars), 1995-01 , Vol. 320 , N. 1 , P. 47-54

Droits : Académie des Sciences
http://archimer.ifremer.fr/doc/00183/29454/27856.pdf
http://archimer.ifremer.fr/doc/00183/29454/

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
Hydrothermal circulation at ultramafic-hosted sites supports a large variety of high-and low-temperature hydrothermal vents and associated ecosystems. The discovery of abundant fossil vesicomyid and thyasirid shell accumulations at the ridge crest, approximately 2.5 km east of the active Rainbow vent field on the Mid-Atlantic Ridge (MAR, 36 degrees 13'N), increased our knowledge regarding the diversity of vent communities at slow spreading ridges. Bivalve molluscs of the family Vesicomyidae were represented by the genus Phreagena. Here we present the first record of this genus in the Atlantic Ocean. This second vesicomyid species known from the MAR, Phreagena sp., was found to be associated with a Thyasira species that is affiliated with T. southwardae (at the Logatchev vent field on the MAR) and with T. vulcolutre (in the Gulf of Cadiz). These two clams have close relationships with seep taxa along the continental margin, and were likely associated with sedimented vent fields. delta O-18 and delta C-13 analyses of the shells suggested that the burrowing bivalve Thyasira could incorporate isotopically light carbon, derived from the oxidation of methane in the sediment, while the signature of Phreagena sp. shells denoted a different carbonate source. C-14 dating of the shells denoted that the hydrothermal activity in the Rainbow area began at least similar to 25.5 kyr BP, which is similar to the model of the hydrothermal vent field distribution that was proposed for the Logatchev hydrothermal site. The results provide new insight regarding the diversity of chemosynthetic fauna on the MAR over geologic time. Ultramafic-hosted, on-axis sedimented vent fields extend the range of habitats for chemosynthetic communities, underlying the need to further explore the geology of these types of environments on slow-spreading ridges and to determine their role in the ecology of deep-sea vent communities.
ISSN: 1525-2027

hal-00523467
https://hal.archives-ouvertes.fr/hal-00523467
https://hal.archives-ouvertes.fr/hal-00523467/document
https://hal.archives-ouvertes.fr/hal-00523467/file/G3-Lartaud-_-al.pdf
DOI : 10.1029/2010GC003079

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Until now, the culture of sulphur-oxidizing bacterial symbionts associated with marine invertebrates remains impossible. Therefore, few studies focused on symbiont's physiology under stress conditions. In this study, we carried out a comparative experiment based on two different species of lucinid bivalves (Codakia orbiculata and Lucina pensylvanica) under comparable stress factors. The bivalves were starved for 6months in sulphide-free filtered seawater. For C.orbiculata only, starved individuals were then put back to the field, in natural sediment. We used in situ hybridization, flow cytometry and X-ray fluorescence to characterize the symbiont population hosted in the gills of both species. In L.pensylvanica, no decrease in symbiont abundance was observed throughout the starvation experiment, whereas elemental sulphur slowly decreased to zero after 3months of starvation. Conversely, in C.orbiculata, symbiont abundance within bacteriocytes decreased rapidly and sulphur from symbionts disappeared during the first weeks of the experiment. The modifications of the cellular characteristics (SSC - relative cell size and FL1 - genomic content) of the symbiotic populations along starvation were not comparable between species. Return to the sediment of starved C.orbiculata individuals led to a rapid (2-4weeks) recovery of symbiotic cellular characteristics, comparable with unstressed symbionts. These results suggest that endosymbiotic population regulation is host-species-dependent in lucinids.
ISSN: 0168-6496

hal-01545911
https://hal.archives-ouvertes.fr/hal-01545911
DOI : 10.1111/1574-6941.12366

Éditeur(s) : Springer
Résumé : The transforming growth factor (TGF)-beta superfamily is a group of important growth factors involved in multiple processes such as differentiation, cell proliferation, apoptosis and cellular growth. In the Pacific oyster Crassostrea gigas, the oyster gonadal (og) TGF-beta gene was recently characterized through genome-wide expression profiling of oyster lines selected to be resistant or susceptible to summer mortality. Og TGF-beta appeared specifically expressed in the gonad to reach a maximum when gonads are fully mature, which singularly contrasts with the pleiotropic roles commonly ascribed to most TGF-beta family members. The function of og TGF-beta protein in oysters is unknown, and defining its role remains challenging. In this study, we develop a rapid bacterial production system to obtain recombinant og TGF-beta protein, and we demonstrate that og TGF-beta is processed by furin to a mature form of the protein. This mature form can be detected in vivo in the gonad. Functional inhibition of mature og TGF-beta in the gonad was conducted by inactivation of the protein using injection of antibodies. We show that inhibition of og TGF-beta function tends to reduce gonadic area. We conclude that mature og TGF-beta probably functions as an activator of germ cells development in oyster.
Marine Biotechnology (1436-2228) (Springer), 2011-10 , Vol. 13 , N. 5 , P. 971-980

Droits : Springer Science+Business Media, LLC 2011
http://archimer.ifremer.fr/doc/00042/15371/13438.pdf
DOI:10.1007/s10126-010-9361-4
http://archimer.ifremer.fr/doc/00042/15371/

Éditeur(s) : HAL CCSD National Shellfisheries Association
Résumé : International audience
Monitoring gonad maturation for protandrous and functional hermaphrodite species such as the giant clam Tridacna maxima is difficult due to the juxtaposition and relative proportion of male and female tissues in the gonad [gonadal sex ratio (GSR)]. Here, the relevance of the widely used gonadosomatic index (GSI) as proxy of giant clam gonad maturation is tested with a large dataset (n ¼ 265). Gonadosomatic index is compared with other indices, namely the proportion of the male part harboring spermatozoids, the proportion of empty oocyte follicles, the mean oocyte diameter, and the oocyte elongation. At gonad scale, high index variability highlighted partial spawning. At individual scale, male and female maturation proxies were contrasted, showing either asynchronous emissions of male and female gametes or contrasted spermatogenesis and oogenesis duration. The GSI was mostly driven by the number and diameter of oocytes and therefore it is recommended here as primary proxy for female maturity. Except for the oocyte elongation, all indices were affected by the GSR, which ruled out drawing conclusions at population scale. These results highlight the need for maturation stage proxies that are optimized for functional hermaphrodite species.
ISSN: 0730-8000

hal-01613648
https://hal.archives-ouvertes.fr/hal-01613648
https://hal.archives-ouvertes.fr/hal-01613648/document
https://hal.archives-ouvertes.fr/hal-01613648/file/Gaertner-Mazouni-2016-eio.pdf
DOI : 10.2983/035.035.0107

Résumé : La zone latérale des filaments branchiaux des bivalves Codakia orbiculata et Lucina pensylvanica est le lieu d'une symbiose chimioautotrophe avec des bactéries sulfo-oxydantes hébergées dans des cellules spécialisées, appelées bactériocytes. Dans cette étude, nous nous sommes proposés de déterminer les mécanismes qui sous-tendent la plasticité cellulaire et tissulaire observée au cours des processus de décolonisation et de recolonisation bactérienne. Pour ce faire, des individus collectés dans leur milieu naturel, ont été maintenus au laboratoire dans des bacs d'eau de mer filtrée en absence de nourriture et de soufre réduit, afin de provoquer la décolonisation bactérienne des filaments branchiaux. Lorsque la branchie apparaissait purgée de ses symbiotes, les individus ont été remis dans leur habitat naturel afin de provoquer sa recolonisation. L'analyse des branchies au cours de ces processus a fait appel à des techniques variées (histologie, immunohistochimie, hybridation in situ, cytométrie en flux, dosage des protéines et spectrométrie de fluorescence X). Les résultats obtenus ont permis de montrer que l'acquisition environnementale mise en évidence chez les juvéniles des Codakia se poursuivait tout au long de la vie des adultes. Cette étude a également permis une meilleure compréhension des mécanismes tissulaires sous-jacents à la plasticité du filament branchial en mettant en évidence les processus d'apoptose et de prolifération cellulaire qui ont lieu au cours des processus de décolonisation et de recolonisation. Ces processus s'accompagnent d'une variation de la teneur en soufre élémentaire, ainsi que de la taille relative et du contenu génomique des symbiotes
The lateral zone of gills filaments of coastal bivalves Codakia orbiculata and Lucina pensylvanica is the site of chemoautotrophic symbiosis with sulfur-oxidizing bacteria, housed in specialized cells called bacteriocytes. The objective of this thesis is to determine the mechanisms underlying cel1 plasticity and tissue plasticity observed in the lateral zone of gills filaments during the processes of bacterial decolonization and recolonization. In order to do this, the individuals collected in their natural habitat were maintained at the laboratory in seawater filtered tanks, without food and reduced sulfur, to cause bacterial decolonization. When the gills seemed to be purged, the individuals were returned to their natural habitat in order to cause the bacterial recolonization of gills filaments. The analysis of the gills during these processes involves several techniques (histology, immunohistochemistry, molecular hybridization, flow cytometry, total protein assays, protein sulfur assays, X-ray fluorescence spectrometry).This study shows that symbiont acquisition can occur during the entire life of Codakia bivalves. It also allows a better understanding of gills filaments plasticity by highlighting apoptosis and cell proliferation during decolonization and recolonization processes.Theses processes are accompanied with of elemental sufur, relative size and genomic content of symbiontes.

http://www.theses.fr/2011AGUY0461/document