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See detailFirst insights into the gut microflora associated with an echinoid from wood falls environments
Becker, Pierre; Samadi, Sarah; Zbinden, Magali et al

in Cahiers de Biologie Marine (2009), 50

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See detailWood-based diet and gut microflora of a galatheid crab associated with Pacific deep-sea wood falls
Hoyoux, Caroline ULg; Zbinden, Magali; Samadi, Sarah et al

in Marine Biology (2009)

Wood falls in the deep sea have recently become the focus of studies showing their importance as nutrients on the deep-sea Xoor. In such environments, Crustaceans constitute numerically the second-largest ... [more ▼]

Wood falls in the deep sea have recently become the focus of studies showing their importance as nutrients on the deep-sea Xoor. In such environments, Crustaceans constitute numerically the second-largest group after Mollusks. Many questions have arisen regarding their trophic role therein. A careful examination of the feeding appendages, gut contents, and gut lining of Munidopsis andamanica caught with wood falls revealed this species as a truly original detritivorous species using wood and the biofilm covering it as two main food sources. Comparing individuals from other geographic areas from substrates not reported highlights the galatheid crab as specialist of refractory substrates, especially vegetal remains. M. andamanica also exhibits a resident gut microXora consisting of bacteria and fungi possibly involved in the digestion of wood fragments. The results suggest that Crustaceans could be full-fledged actors in the food chains of sunken-wood ecosystems and that feeding habits of some squat lobsters could be different than scavenging. [less ▲]

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See detailPolyolefin matrixes with permanent antibacterial activity: preparation, antibacterial activity, and action mode of the active species
Lenoir, Sandrine; Pagnoulle, Christophe; Galleni, Moreno ULg et al

Poster (2008, May 22)

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See detailKarsts in sandstones and quartzites of Minas Gerais, Brazil
Willems, Luc ULg; Rodet, Joël; Pouclet, André et al

in Cadernos do Laboratorio Xeolóxico de Laxe (2008), 33

The state of Minas Gerais (Brazil) is characterized by significant karst regions, which develop <br /><br />in both sandstone and quartzite terrains and display complex suites of underground and ... [more ▼]

The state of Minas Gerais (Brazil) is characterized by significant karst regions, which develop <br /><br />in both sandstone and quartzite terrains and display complex suites of underground and surfaceforms. In the Espinhaço Ridge, Central Minas Gerais, several caves of up to a few hundred metres long, occur in the surroundings of the town of Diamantina. Some of these caves, such as Salitre actually consist of swallow-holes. Other horizontal caves are characterized by corrosion forms generated in the phreatic zone. In some places, such as in the Rio Preto area, these phreatic forms are overprinted by ceiling tubes, suggesting a polyphase karst evolution, prior to the draining in the cave. Remains of paths, with circular cross section up to one metre in diameter, can be found through residual tower-like surface landforms widely present in the landscapes. Their dissection is due to a generalised karstification in the area, resulting in closed canyons, megakarrens and kamenitzas. In Southern Minas Gerais, close to the Mantiqueira Ridge, the caves of the Ibitipoca state park can reach more than 2 km in length. These caves are associated with a very large hanging geological syncline. Several of these caves contain active streams, which flow for hundreds of metres before disappearing in sand-choked passages. Keyhole cross sections characterize steeply descending passages in these caves, indicatinga chan ge from slow phreatic flow towards a faster vadose flow responsible for the vertical incision of the passage. Such change is probably related to base level lowering and/or to turn in the direction of the water flow. Several generations of wall-pockets, from a few centimetres to over a metre long, occur into the caves. These features are good indicators of the initial phase of speleogenesis, generating the initial conduits by their coalescence. This mechanism is also responsible for cut-off meanders. In the area, the main river flows along the syncline axis and cuts through a rock barrier, generating a tunnel-like passage. This cave drains, through resurgences in its walls, part of the water that flows in other caves located in the flank of the syncline. [less ▲]

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See detailMorphological alterations of zooxanthellae in bleached cnidarian hosts
Ladrière, Ophélie ULg; Compère, Philippe ULg; Decloux, Nicole ULg et al

in Cahiers de Biologie Marine (2008), 49(3), 215-227

Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four ... [more ▼]

Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four coral species-three collected from a barrier reef in Madagascar (Acropora digitifera (Dana, 1846), Echinopora hirsutissima Milne-Edwards & Haime, 1849 and Porites (Synaraea) rus Forskal, 1775)) and one cut from an aquarium-grown coral (Pocillopora damicornis (Linnaeus, 1758)-and from the hermatypic (zooxanthellae-containing) sea anemone Aiptasia pulchella (Carlgren, 1943). Zooxanthellae from bleached animals showed different stages of degradation or disorganization. Some were free, detached from the host gastroderm, associated or not with host-cell remains. Others were vacuolated, with abundant reserve material globules and angular holes probably created by the loss of crystalline material during cutting. Experimentally heat-shocked P. damicornis harboured, moreover, a greater number of dividing algae. Bleached individuals were found to vary as regards their response to stress, and zooxanthellae expelled from heat-shocked anemones showed a greater mitotic index and a higher survival rate than algae extracted or naturally externalized from healthy individuals. We propose a combination of morphological criteria for use in diagnosing the health state of algae-cnidarian symbiosis, so vulnerable in the case of bleaching. [less ▲]

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See detailThe rocker bone: a new kind of mineralised tissue?
Parmentier, Eric ULg; Compère, Philippe ULg; Casadevall, Margarida et al

in Cell & Tissue Research (2008), 334

In some Ophidiiform fishes, the anterior part of the swimbladder is thickened into a hard structure called the “rocker bone”, which is thought to play a role in sound production. Although this structure ... [more ▼]

In some Ophidiiform fishes, the anterior part of the swimbladder is thickened into a hard structure called the “rocker bone”, which is thought to play a role in sound production. Although this structure has been described as cartilage or bone, its nature is still unknown. We have made a thorough analysis of the rocker bone in Ophidion barbatum and compared it with both classical bone and cartilage. The rocker bone appears to be a new example of mineralisation. It consists of (1) a ground substance mainly composed of proteoglycans (mucopolysaccharide acid) and fibres and (2) a matrix containing small mineralised spherules composed of a bioapatite and fibrils. These spherules are embedded in mineralised cement of a similar composition to the spherules themselves. The rocker bone grows via the apposition of new apatite spherules at its periphery. These spherules are first secreted by the innermost fibroblast layer of the capsule contained in the rocker bone and then grow extracellularly. Blood vessels, which represent the only means of transport for matrix and mineral material, are numerous. They enter the rocker bone via the hyle and ramify towards the capsule. We propose to call this new kind of mineralised tissue constituting the rocker bone “frigolite” (the Belgian name for styrofoam) in reference to the presence of spherules of different sizes and the peculiarity of the rocker bone in presenting a smooth surface when fractured. [less ▲]

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See detailThe tropical sea anemone Aiptasia pallida as a lab model for the study of coral bleaching
Ladrière, Ophélie ULg; Roberty, Stéphane ULg; Baudesson, Charlotte et al

Poster (2008)

Bleaching is still among major events threatening coral reefs. New tools have to be developped to better understand the mechanisms leading to this pathology : we studied the use of the hermatypic anemone ... [more ▼]

Bleaching is still among major events threatening coral reefs. New tools have to be developped to better understand the mechanisms leading to this pathology : we studied the use of the hermatypic anemone Aiptasia pallida as experimental model for coral bleaching. Aiptasia appears as a good candidate as it is easy to maintain in aquarium and subjected to bleaching like corals. Both morphological and physiological approaches were performed to investigate the ultrastructure of the anemone tissues (TEM) and the zooxanthellae photophysiology (chlorophyll a fluorescence, respiration and pigmentation). Experiments under light and dark stress reveal that anemone tissues ultrastructure can be differently affected. In darkness, the ectoderm activity is reoriented to capture prey by increasing cnidocyte density. In contrast, intense light affects especially the gastroderm : intercellular spaces increase, the expulsion of intact algae in the gastric cavity and the degradation of zooxanthellae inside vacuoles seem to reduce the zooxanthellae density, chloroplast thylakoids lose their parallel arrangement. The analysis of the fluorescence induction curve appears as a powerful tool to analyse the physiological events series previous to bleaching. Although no significant zooxanthellae density reduction was observed, the decrease of pigments concentrations indicates that light or dark stresses induce anemone bleaching. Under strong light intensity, A. pallida zooxanthellae show an increased proportion of PSII QB non reducing, leading to partial photoinhibition. This phenomenon favours the ROS production that damages cellular structures of host and zooxanthellae. In darkness, there is no photosynthesis; anemones have therefore to find other feeding sources, as suggested by the ultrastructural approach. As the present results confirm some of those obtained on scleractinians, A. pallida can be regarded as a good model for coral bleaching studies and has numerous advantages for experimentation. [less ▲]

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See detailIron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata
Corbari, Laure; Cambon-Bonavita, Marie-Anne; Long, Gary et al

in Biogeosciences (2008), 5

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See detailBacterial symbionts and mineral deposits in the branchial chamber of the hydrothermal vent shrimp Rimicaris exoculata: relationship to moult cycle
Corbari, Laure; Zbinden, Magali; Cambon-Bonavita, Marie-Anne et al

in Aquatic Biology (2008), 1

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See detailDiet of crustaceans species associated to deep-sea wood falls
Hoyoux, Caroline ULg; Samadi, Sarah; Zbinden, Magali et al

Poster (2007, November 16)

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See detailKarsts in sandstones and quatrzites of Minas Gerais, Brazil
Willems, Luc ULg; Rodet, J.; Pouclet, A. et al

Poster (2007)

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See detailPolyphase karst system in Cretaceous chalk and calcarenite of the Belgian-Dutch border
Willems, Luc ULg; Rodet, Joël; Fournier, Matthieu et al

in Zeitschrift für Geomorphologie (2007), 51(3), 361-376

Along the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation ... [more ▼]

Along the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation allows the reconstruction of the genesis of an original karst system resulting from the merging of initially independent endokarsts and exokarsts. Deep weathering has developed within the Cretaceous formations, creating nodes of weathered chalk and closed cavities. These phenomena are expanded over time and can form interconnected voids. Near the surface, solution pipes are generated under the coarsest deposits of a fluvial terrace capping the Cretaceous formations. These pipes develop vertically and may be related to the progressive lowering of the water table in connection with the incision of the Meuse valley. Some of these phenomena cut up the older endokarsts and organize complex systems of out-flow within the chalk. [less ▲]

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See detailPolyolefin matrixes with permanent antibacterial activity : preparation, antibacterial activity, and action mode of the active species
Lenoir, Sandrine ULg; Pagnoulle, Christophe; Galleni, Moreno ULg et al

in Biomacromolecules (2006), 7(8), 2291-2296

Poly[2-(tert-butylamino)ethyl methacrylate] (PTBAEMA) belongs to a novel class of water-insoluble biocides. Dispersion of a poly(ethylene-co-butylene)-b-poly[2-(tert-butylamino)ethyl methacrylate] diblock ... [more ▼]

Poly[2-(tert-butylamino)ethyl methacrylate] (PTBAEMA) belongs to a novel class of water-insoluble biocides. Dispersion of a poly(ethylene-co-butylene)-b-poly[2-(tert-butylamino)ethyl methacrylate] diblock copolymer (PEB-b-PTBAEMA) within low-density polyethylene (LDPE) imparts antimicrobial properties to the polyolefin as assessed by the viable cell counting method against Escherichia coli (E. coli). This diblock copolymer has been synthesized by atom transfer radical polymerization (ATRP) with a poly(ethylene-co-butylene) (PEB) oligomer end-capped by an activated bromide as a macroinitiator for the polymerization of 2-(tert-butylamino)ethyl methacrylate (TBAEMA). Morphological changes of E. coli bacteria in contact with modified LDPE have been observed by transmission and scanning electron microscopy and indicate that the diblock copolymer is bactericide rather than bacteriostatic. Finally, the action mode of the PEB-b-PTBAEMA copolymer more likely relies on the displacement of the Ca2+ and/or Mg2+ ions of the outer membrane of the bacteria, which is disorganized and finally disrupted. [less ▲]

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See detailBranchial chamber tissues in two caridean shrimps: the epibenthic Palaemon adspersus and the deep-sea hydrothermal Rimicaris exoculata
Martinez, A. S.; Charmantier, G.; Compère, Philippe ULg et al

in Tissue & Cell (2005), 37(2), 153-165

The structure of the epithelia of the branchial chamber organs (gills, branchiostegites, epipodites) and the localization of the Na2+,K2+-ATPase were investigated in two caridean shrimps, the epibenthic ... [more ▼]

The structure of the epithelia of the branchial chamber organs (gills, branchiostegites, epipodites) and the localization of the Na2+,K2+-ATPase were investigated in two caridean shrimps, the epibenthic Palaemon adspersus and the deep-sea hydrothermal Rimicaris exoculata. The general organization of the phyllobranchiate gills, branchiostegites and epipodites is similar in P. adspersus and in R. exoculata. The gill filaments are formed by a single axial epithelium made of H-shaped cells with thin lateral expansions and a basal lamina limiting hemolymph lacunae. In P. adspersus, numerous ionocytes are present in the epipodites and in the inner-side of the branchiostegites; immunofluorescence reveals their high content in Na+,K+-ATPase. In R. exoculata, typical ionocytes displaying a strong Na+,K+-ATPase specific fluorescence are observed in the epipodites only. While the epipodites and the branchiostegites appear as the main site of osmoregulation in P. adspersus, only the epipodites might be involved in ion exchanges in R. exoculata. In both species, the gill filaments are mainly devoted to respiration. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailOpal-a Speleothems of Wei-Assipu-Tepui, Roraima Province, Brazil
Urbani, Franco; Compère, Philippe ULg; Willems, Luc ULg

in Boletín de la Sociedad Venezolana de Espeleología (2005), 39

Bol. Soc. Venezolana Espel. v.39 Caracas dic. 2005 ®download el artículo en el formato PDF Como citar este artículo Opal-a Speleothems of Wei-Assipu-Tepui, Roraima Province, Brazil Franco Urbani1 ... [more ▼]

Bol. Soc. Venezolana Espel. v.39 Caracas dic. 2005 ®download el artículo en el formato PDF Como citar este artículo Opal-a Speleothems of Wei-Assipu-Tepui, Roraima Province, Brazil Franco Urbani1, Phillipe Compère2 & Luc Willems2 1Universidad Central de Venezuela. Fac. Ingeniería. Escuela de Geología. Lab. de Geología y Geoquímica. Caracas 1053 y Sociedad Venezolana de Espeleología. Apartado 47028. Caracas 1041A. urbani@cantv.net 2Université de Liège, Laboratoire de Morphologie Ultrastructurale, Département des sciences et gestion de l'environnement, allée de la Chimie, 3, B-4000 Liège 1,Belgium. 3University of Liège. Laboratoire de Pétrologie Sédimentaire, Département de Géologie, B20, B-4000 Liege, Belgium.Lucwillems65@versateladsl.be ABSTRACT Coralloid-shaped speleothems samples were collected from a small cave in a mountain of the Roraima massif, Brazil. They were mineralogically identified as opal-A and show two concentric growth zones: A massive light colored inner one, and a darker outer zone with a spongy texture. On the surface the presence of some filaments probably of algae suggest biomineralisation. Chemically the outer zone shows impurities with high values of Cl and P. The leaching of bird nest guano may be the source of P. The two zones were probably formed in two different climatic conditions, the outer one in the current wet and vegetated period, and the inner zone during a former drier period. [less ▲]

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See detailCarste em Quartzito de Região de Diamantina : Gruta do Salitre e Parque Estadual do Rio Preto, Minas Gerais
Willems, Luc ULg; Rodet, J.; Pouclet, A. et al

Poster (2004)

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See detailChapter 3, The Integument : Morphology and Biochemistry
Compère, Philippe ULg; Jeuniaux, Charles; Goffinet, Gerhard ULg

in Forest, J.; von Vaupel Klein, J. C.; Schram, F. R. (Eds.) The Crustacea revised and updated from the Traité de Zoologie Vol 1 (2004)

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See detailDistribution of bacteria and associated minerals in the gill chamber of the vent shrimp Rimicaris exoculata and related biogeochemical processes
Zbinden, M.; Le Bris, N.; Gaill, F. et al

in Marine Ecology. Progress Series (2004), 284

The shrimp Rimicaris exoculata dominates the megafauna of some Mid-Atlantic Ridge hydrothermal vent fields. This species harbours a rich bacterial epibiosis inside its gill chamber. At the 'Rainbow' vent ... [more ▼]

The shrimp Rimicaris exoculata dominates the megafauna of some Mid-Atlantic Ridge hydrothermal vent fields. This species harbours a rich bacterial epibiosis inside its gill chamber. At the 'Rainbow' vent site (36degrees 14.0'N), the epibionts are associated with iron oxide deposits. Investigation of both bacteria and minerals by scanning electron microscopy (SEM) and X-ray microanalysis (EDX) revealed 3 distinct compartments in the gill chamber: (1) the lower pre-branchial chamber, housing bacteria but devoid of minerals; (2) the 'true' branchial chamber, containing the gills and devoid of both bacteria and minerals; and (3) the upper pre-branchial chamber, housing the main ectosymbiotic bacterial community and associated mineral deposits. Our chemical and temperature data indicated that abiotic iron oxidation appears to be kinetically inhibited in the environment of the shrimps, which would explain the lack of iron oxide deposits in the first 2 compartments. We propose that iron oxidation is microbially promoted in the third area. The discrepancy between the spatial distribution of bacteria and minerals suggests that different bacterial metabolisms are involved in the first and third compartments. A possible explanation lies in the modification of physico-chemical conditions downstream of the gills that would reduce the oxygen content and favours the development of bacterial iron-oxidizers in this Fe-II-rich environment. A potential role of such iron-oxidizing symbionts in the shrimp diet is suggested. This would be unusual for hydrothermal ecosystems, in which most previously described symbioses rely on sulphide or methane as an energy source. [less ▲]

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See detailComparative degradation rates of chitinous exoskeletons from deep-sea environments
Ravaux, J.; Zbinden, M.; Voss-Foucart, M. F. et al

in Marine Biology (2003), 143(2), 405-412

Hydrothermal vent environments, particularly those associated with the vestimentiferan Riftia pachyptila, are believed to be among the highest chitin-producing systems. In order to elucidate the chitin ... [more ▼]

Hydrothermal vent environments, particularly those associated with the vestimentiferan Riftia pachyptila, are believed to be among the highest chitin-producing systems. In order to elucidate the chitin cycle in these environments, we estimate the in situ chitin degradation rates of tube-worm exoskeletons. Our in situ experiments show that the tubes of Riftia are highly stable structures. Comparative measurements of the degradation rates of Riftia tubes and crab shells immersed at deep-sea vents show that the tubes would be degraded within 2.5 years, whereas the time for the total degradation of the vent crab (Bythograea thermydron) carapaces would not exceed 36 days. The importance of the microbial participation in this degradation was estimated for Riftia tubes. Based on previous work, we calculated chitin production by a population of Riftia tubes of about 750 g m(-2) year(-1) (763). From our in situ experiments, we estimated a microbial chitinolysis rate of about 500 g m(-2) year(-1) (496) (65% of the chitin produced). Exoskeletons containing beta-chitin appear more stable in natural environments than those containing alpha-chitin and would thus be less available as carbon and nitrogen sources. In contrast, isolated beta-chitin was hydrolysed faster than alpha-chitin during in vitro degradation experiments; for instance, Riftia beta-chitin was degraded about 3- to 4-fold faster than Bythograea alpha-chitin. A stabilization process by disulfide bonds of the proteins-chitin link, rather than the crystalline form of the chitin (alpha/beta), accounts for the resistance of Riftia tubes to enzymatic attacks. [less ▲]

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