Digenean trematode species in the cockle cerastoderma edule: Identification key and distribution along the North-Eastern Atlantic Shoreline
We describe the digenean fauna of one of the dominant intertidal hosts, the common cockle Cerastoderma edule, in terms of biomass, off north-eastern Atlantic shores. Using published and unpublished literature we have prepared an identification key and provide an up-date of the large-scale distributional patterns of digenean species of the common cockle. At least sixteen digenean species, belonging to seven families, use cockles as intermediate host. Among these species two utilize cockles as first intermediate host only, whereas two species utilize cockles as both first and second intermediate host. The remaining eleven species have cockles as their second intermediate host. Water birds and fish are the definitive hosts to twelve and four species, respectively.Cockles are infected with digeneans along the latitudinal gradient from southern Morocco to the western region of the Barents Sea often with high infection levels. Whereas some of these digenean species occur along most of the latitudinal gradient others show a more restricted northern or southern distribution mostly caused by an underlying latitudinal gradient of host species.Knowledge of digenean species and their large-scale distribution pattern may serve as a baseline for future studies dealing with the effects of climate change on parasite–host systems. For such studies the cockle and its digenean community could be an ideal model system.
(Journal of the Marine Biological Association of the United Kingdom. vol. 89, n° 0025-3154, pp. 543, 26/03/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Biodynamics, subcellular partitioning, and ultrastructural effects of organic selenium in a freshwater bivalve
Selenium is a trace element characterized by concentrations that narrowly range between being essential and being toxic. Even though inorganic selenite and selenate are the predominant chemical forms of Se in surface waters, the toxicity of Se to aquatic organisms is mostly governed by the bioavailability of organic selenium within food webs. The present study was designed to evaluate organic selenium bioaccumulation and toxicity patterns in the freshwater sentinel species Corbicula fluminea. Waterborne selenomethionine (SeMet) exposure was used to mimic dietary organo-Se uptake. Our results demonstrate that SeMet is accumulated to a relatively high extent with a concentration factor of 770 (wet weight basis). Higher uptake than depuration rates suggest that bivalves deal with high Se amounts using a strategy of detoxification based on Se sequestration that could involve granules, as shown by a strong increase of Se in the particulate subcellular fraction. Selenium is persistent in the cytosol of bivalves exposed to SeMet where it is found in proteins of a wide range of molecular mass, indicating a possible replacement of methionine by selenomethionine. A subsequent alteration of protein function might be one of the mechanisms of Se toxicity that could explain the histopathological effects we observed in gills by using transmission electronic microscopy. Those analyses showed changes in gill filament ultrastructure and suggested mitochondria as the first target for SeMet cytotoxicity, with alterations of the outer membrane and of cristae morphology. Organo-Se would thus not only be toxic via indirect mechanisms of maternal transfer as it was suggested for fish but also directly. Our results on Se distribution agree with studies that used dietary Se transfer, and highlight the relevance (and less expensive way) of using SeMet water-only exposure protocols to mimic the real environment. © 2009 American Chemical Society.
(Environmental Science and Technology. vol. 43, n° 0013-936X, pp. 2112-2117, 15/03/2009)
IRSN/DEI/SECRE/LRE, IRSN/DEI/SECRE, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Properties of fluorescent dissolved organic matter in the Gironde Estuary
The isolation, characterization and study of the properties of aquatic dissolved organic matter (DOM) still represent a challenge because of the heterogeneity, complexity and low concentration of organic material in natural waters. Based on its ability to interact with contaminants and thus to modify their transport and bioavailability, DOM is of interest for environmental purposes. The objective of this work was to better characterize DOM in the Gironde Estuary (southwestern France). The estuary represents an exchange zone between the continent and the Atlantic Ocean and conditions the transfer of organic and inorganic substances from the continental to the oceanic environment. Several samples were collected along the estuary during three cruises in 2002 and 2006. They were analysed using excitation-emission matrix (EEM) spectroscopy, a sensitive technique that allows direct analysis of water samples. Fluorescent DOM and dissolved organic carbon (DOC) did not behave conservatively in this estuarine system, i.e. the organic material did not undergo simple dilution from the upstream to the downstream part of the estuary. A seasonal variability in DOC content was pointed out, whereas few seasonal variations in DOM fluorescence were observed. DOM sources and processing in the estuary were further evaluated by determining two fluorescence indices - the humification index (HIX) and the index of recent autochthonous contribution (BIX). By applying these indices, the relative degree of humification (HIX) and autotrophic productivity (BIX) could be assessed. Based on the fluorescence and DOC results, the estuary was divided into three zones depending on salinity (S) and characterized by specific DOM: (i) A turbid zone of low salinity (S < 5) and high suspended particulate matter concentration with increase in the intensities of the α′ and α fluorophores, characteristic of humic-like compounds. (ii) A mid-estuarine zone (5 < S < 25) characterized by low autotrophic productivity and containing strongly degraded organic material, as shown by the low values of BIX and high values of HIX. (iii) A higher salinity area (S > 25) characterized by increased autotrophic productivity and a marked marine influence, and associated with high and low values of BIX and HIX, respectively. The HIX and BIX indices were shown as useful tools for readily defining and classifying DOM characteristics in estuarine waters.
(Organic Geochemistry. vol. 40, n° 0146-6380, pp. 706-719, 12/03/2009)
ISM, UB, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Digenean trematodes–marine mollusc relationships: a stable isotope study
The stable carbon and nitrogen isotopic composition of digenean trematode parasites and their marine mollusc hosts was investigated to describe the potential influence of parasites on their host and its different tissues, and to obtain further insight into their trophic relationships. Four parasite–host systems were studied: Labratrema minimus–Cerastoderma edule, Monorchis parvus–C. edule, Lepocreadiidae parasites–Nassarius reticulatus and Zoogonidae parasites–N. reticulatus. Among the 4 sampling occasions reported here and corresponding to the 4 parasite–host systems, isotopic shifts from pathologic (i.e. linked to disturbances in host metabolism) and mass-balance (i.e. linked to significant differences between host and parasite isotopic signatures) origins were observed only once. Both corresponded to δ13C measurements of the L. minimus–C. edule system when the infestation load (percentage parasite dry weight compared to total flesh dry weight) was highest (9 to 25%, mean = 16%) over the sampling period. Overall, measurements indicate that digenean trematode parasitism induced low or no shifts in isotopic signatures of C. edule and N. reticulatus tissues. The 2 endoparasites L. minimus and M. parvus appeared to be slightly depleted in 13C compared to C. edule digestive gland and gonads, which were the most parasitized tissues. In contrast, no fractionation or low 15N trophic enrichments occurred in the parasites. These results highly contrast with the classical trophic enrichment reported in prey–predator systems but are in agreement with the scarce literature regarding other parasite–host systems. Our results indicate that (1) digenean trematodes mainly feed on digestive glands (the cockle tissue with which they are mainly associated) with a possible slight preference for lipids, and (2) fractionation due to parasite metabolism should be low due to abbreviated metabolic pathways and/or slight loss of materials through excretion, tegument diffusion and respiration.
(Diseases of Aquatic Organisms. vol. 84, n° 0177-5103, pp. 65-77, 09/03/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
Deconvolution of trace element (As, Cr, Mo, Th, U) sources and pathways to surface waters of a gold mining-influenced watershed.
The Upper Isle River (SW France) drains the second most productive gold-mining district of France. A high resolution survey during one hydrological year of As, Cl(-), Cr, Fe, Mn, Mo, SO(4)(2-), Th and U dissolved concentrations in surface water aimed to better understand pathways of trace element export to the river system downstream from the mining district. Dissolved concentrations of As (up to 35000 ng/L) and Mo (up to 292 ng/L) were about 3-fold higher than the regional dissolved background and showed a negative logarithmic relation with discharge. Dissolved concentrations of Cr (up to 483 ng/L), Th (up to 48 ng/L) and U (up to 184 ng/L) increased with discharge. Geochemical relationships between molar ratios in surface water, geochemical background as well as rain- and groundwater data were combined. The contrasting behavior of distinct element groups was explained by a scenario involving three seasonal components: (i) The high flow component is poorly concentrated in As and Mo but highly concentrated in Cr, Th, U. This has been attributed to diffuse sources such as water-soil interactions, atmospheric inputs, bedrock and bed sediment weathering. Although this component probably also includes a contribution by weathering of sulfide veins, this signal is masked by dilution. (ii) One low flow component presents high SO(4)(2-), Fe, As and Mo and moderate Cr, Th and U concentrations. This component has been attributed to point sources such as mine gallery effluents, mining waste weathering and groundwater inputs from natural and/or mining-induced sulfide oxidation in the ore deposit. (iii) A second low flow component showing high As plus Mo concentrations associated with very low SO(4)(2-), Fe, Cr, Th and U concentrations, probably reflects trace element scavenging by ferric oxyhydroxide formation in the adjacent aquifer. This is supported by the decrease of Fe, Cr, Th and U in surface waters. Flux estimates suggest contrasting element-specific impacts on annual dissolved fluxes. Runoff may account for the major part of annual dissolved As, Mo, Th and U fluxes in the Upper Isle River. Inputs related to sulfide oxidation respectively contributed approximately 30% and approximately 24% to annual As and Mo fluxes. The formation of ferric oxyhydroxides strongly retained Cr, Th and U during the low flow, limiting their dissolved concentrations in surface waters. If this process may eventually decrease As mobility, its impact on dissolved As concentrations in surface water may be limited or/and counterbalanced by As release during sulfide oxidation.
(Science of the Total Environment. vol. 407, n° 0048-9697, pp. 2063-76, 01/03/2009)
GRESE, UNILIM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Stable isotopes changes in the adductor muscle of diseased bivalve Ruditapes philippinarum
In this article, we show how a disease could bias stable isotope analyzes of trophic networks and propose a strategy in the choice of tissues to be analyzed. In the past few years, a new pathology (brown muscle disease or BMD) affecting the posterior adductor muscle of Ruditapes philippinarum has emerged in Arcachon Bay. BMD induces a necrosis of muscle tissues which become infused by conchiolin and hence calcified. As muscle of mollusks are often used for trophic food webs studies through stable isotopic analyzes, this work investigated the effect of BMD on carbon and nitrogen isotopic ratios of anterior and posterior adductor muscles of clams collected in February and August 2007. Infected clams displayed a lower condition index and a posterior adductor muscle δ13C enrichment of 1.2‰ in February and 0.7‰ in August. δ15N of posterior muscles was however not affected by the disease. Anterior muscle of diseased clams remained healthy and displayed the same isotopic signature as both posterior and anterior muscular tissues of healthy clam. Acidification significantly depleted δ13C in posterior muscles of infected clams, suggesting calcification, contrary to anterior muscles of infected clam and to both muscles of healthy clams, where no effect was observed. An X-ray diffractometry analysis confirmed the presence of CaCO3 (aragonite). Trophic food web studies relying on stable isotope ratios should utilize only healthy animals or anterior adductor muscles when expertise in mollusk pathology is lacking.
(Marine Biology. vol. 156, n° 0025-3162, pp. 611 - 618, 01/03/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LIENSs, INSU - CNRS, ULR, CNRS
Impact of lateral transport on organic proxies in the Southern Ocean
K′ Sea-surface temperature BIT index Southern Ocean Lateral transport of fine-grained organic carbon particles can complicate the interpretation of paleoclimate records based on organic proxies. Here we investigated the effect of lateral transport on newly developed temperature and soil organic matter proxies, TEX 86 and BIT index, respectively, in core MD88-769 recovered from the South East Indian Ridge. Our results show that TEX 86 and BIT records in comparison to diatom and foraminifera records were representative for more local climate changes while alkenones and n-alkanes originated from distant areas by oceanic and atmospheric transport, respectively. This suggests that TEX 86 and BIT paleoclimate records are primarily influenced by local conditions and less subjected to long-distance lateral transport than other organic proxies in the Southern Ocean.
(Quaternary Research. vol. 71, n° 0033-5894, pp. 246-250, 01/03/2009)
NIOZ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, NIOZ
Sensory structures of Archaeostraca (Phyllocaridida, Crustacea)
The carapace of some Archaeostraca exhibits two kinds of structures that are best interpreted as corresponding to sensory organs. Dorsal ones are located either along the dorsal margin of the valves of the carapace, or on the median dorsal plate. Anterolateral ones are located in the anterior region of both valves. Both structures are respectively homologous of the anterior and posterior sensory organs known from extant Leptostraca and other Crustacea. These structures are described in adult Archaeostraca from the Ordovician to the Carboniferous. It is expected that they could have baroreceptor, mechanoreceptor, and/or chemoreceptor functions in some cases, and a function in osmotic regulation in others.
(Evolution & Development. vol. 11, n° 1525-142X, pp. 225-232, 24/02/2009)
MNHN, UPMC, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, NRM
A new phyllocarid crustacean from the Famennian of Belgium
A single carapace of an echinocaridid phyllocarid found in the uppermost part of the Evieux Formation at Arbre near Namur of late (latest ?) Famennian age lacks both the posterocentral and posterodorsal ridges, both characters considered to be derived ones. This makes it a member of the E. punctata group. However the lack of any spine or tubercle on the dorsal lobes, along the hinge line, or on the peripheral margin of the carapace, makes the Belgian specimen distinct from all other Famennian echinocaridids. A new genus and species Nervicaris belgica is proposed for this first late Famennian echinocaridid representative from continental Western Europe. This occurrence extends both the vertical range and geographic distribution of echinocaridid phyllocarids.
(Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. vol. 251, n° 0077-7749, pp. 147-153, 19/02/2009)
LDO, INSU - CNRS, UBO EPE, CNRS, UEB, MNHN, UPMC, CNRS, CR2P, MNHN, UPMC, CNRS
Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum
Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations(1). The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2,3). Since that time, several shortcomings of that earlier effort have become apparent(4). Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project(5). We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present(6,7).
(Nature Geoscience. vol. 2, n° 1752-0894, pp. 127-132, 01/02/2009)
PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, ICTA, UAB, ICREA, SCIB - UMR E3, INAC, CEA, UGA [2016-2019], CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, UB, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BCCR, BIO / UiB, UiB, AWI, CALTECH, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, FSS, CEBC, CNRS, MARUM, NOC