Zebrafish genome instability after exposure to model genotoxicants
Sublethal exposure to environmental genotoxicants may impact genome integrity in affected organisms. It is therefore necessary to develop tools to measure the extent and longevity of genotoxicant-induced DNA damage, and choose appropriate model organisms for biomonitoring. To this end, markers of DNA damage were measured in zebrafish larvae and adults following exposure to model genotoxicants (benzo[a]pyrene and ethyl methanesulfonate). Specifically, we assessed primary DNA damage and the existence of potentially persistent genomic alterations through application of the comet assay, quantitative random amplified polymorphic DNA (qRAPD) and amplified fragment length polymorphism (AFLP) assays. Furthermore, expression of genes involved in DNA repair, oxidative stress response and xenobiotic metabolism was evaluated as well. Additionally, the AFLP method was applied to adult specimens 1 year after larval exposure to the genotoxicants to evaluate the longevity of the observed DNA alterations. Large numbers of DNA alterations were detected in larval DNA using the comet assay, qRAPD and AFLP, demonstrating that zebrafish larvae are a sensitive model for revealing genotoxic effects. Furthermore, some of these genomic alterations persisted into adulthood, indicating the formation of stable genomic modifications. qRAPD and AFLP methods proved to be highly sensitive to genotoxic effects, even in cases when the comet assay indicated a lack of significant damage. These results thus support the use of zebrafish larvae as a sensitive model for monitoring the impact of genotoxic insult and give evidence of the longevity of genomic modifications induced by genotoxic agents.
(Ecotoxicology. vol. 24, n° 0963-9292, pp. 887-902, 22/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Present-day sedimentation rates on the southern and southeastern Australian continental margins
The Australian continental margin presents highly contrasted settings depending on (1) the presence or absence of a fluvial sediment supply, (2) the distance from the Australian mainland, and (3) the local hydrological setting. Despite the importance in surface area of the continental margin around the Australian mainland, so far only a few studies have dealt with sedimentation, most of them focusing on the northeastern Australian Shelf. This work presents the first large-scale investigation of modern sedimentation along the southern margin of Australia in the SE Indian Ocean, and the western margin of the Tasman Sea. Sedimentation intensity was assessed on a century timescale using a multi-tracer approach (234Th, 210Pb, 232Th) on interface cores around the 1000 m water depth contour. 234Th (half-life: 24.1 days) in excess was detected in all surface samples, testifying to the occurrence of freshly deposited particles. Sedimentation and mass accumulation rates based on sedimentary 210Pb excess profiles (CF:CS model) range between 0.027 and 0.280 cm y–1 and between 14 and 222 mg cm–2 y–1, respectively. Whereas sedimentation rates are low and associated with carbonates on the western margin, sediments are more influenced by the detrital fraction and organic carbon on the eastern side of the continent. In comparison with northern continental margins (e.g. Timor Sea, Gulf of Papua), the southern Australian margin receives little sediment today, as it is rarely linked to a river system that would otherwise deliver large amounts of sediment, and also because of the presence of the extended shelf south of Australia.
(Australian Journal of Earth Sciences. vol. 62, n° 0812-0099, pp. 143-150, 17/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Tidal bore dynamics in funnel-shaped estuaries
The formation and dynamics of tidal bores in funnel-shaped estuaries is investigated from both a global tidal wave scaling analysis and new quantitative field observations. We show that tidal bore occurrence in convergent estuaries can be estimated from a dimensionless scaling parameter characterizing the relative intensity of nonlinear friction versus local inertia in the momentum equation. A detailed analysis of tidal bore formation and secondary wave structure is presented from a unique long-term database (observations of more than 200 tides) acquired during four campaigns in the two main French tidal-bore estuaries: the Seine and Gironde/Garonne estuaries. We describe the effect of freshwater discharge on the global tidal wave transformation at the estuarine scale and on local tidal bore occurrence in the upper estuary. Our field data suggest that the tidal bore intensity is mainly governed by the dimensionless tidal range, which characterizes the local tidal wave nonlinearity. We also show that the secondary wavefield associated with tidal bore propagating in natural estuaries differs significantly from those associated to undular bores in rectangular channels. In particular, we observe an abrupt decrease of the whelp steepness when the Froude number goes below 1.1. This secondary field transition can explain why tidal bore occurrence in worldwide estuaries is certainly underestimated.
(Journal of Geophysical Research. Oceans. vol. 120, n° 2169-9275, pp. 923-941, 17/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Review: Bucephalus minimus, a deleterious trematode parasite of cockles Cerastoderma spp
Trematodes are the most prevalent and abundant macroparasites in coastal waters. They display a complex life cycle with alternation of free-living and parasitic stages generally involving three host species. The most deleterious stage is in the first intermediate host (a mollusc) where the parasite penetrates as miracidium larvae and asexually multiplicates in sporocysts/rediae to provide cercariae larvae. However, due to basic low prevalence in ecosystems, this system remains difficult to study. Taking the example of the cockle (Cerastoderma edule), an exploited bivalve along North-Eastern Atlantic coasts, and Bucephalus minimus, its most prevalent parasite as first intermediate host, we summarised the 51 most relevant papers (1887-2015). Besides, a 16-year monthly monitoring was performed at Banc d'Arguin (Atlantic coast of France), and allowed to obtain a sufficient number of infected cockles (276 out of 5,420 individuals) in order to provide new information concerning this parasite/host system. Sporocysts (diameter 80-500 μm) and developing cercariae (length 300-500 μm) are not visible before cockle reaches 16-mm shell length and then prevalence increases with host size. Seasonality of infection was not observed but variation of prevalence was significant among years and negatively correlated to the temperature of the former year, which could correspond to the period of infection by miracidium. Seven other species of trematode were identified in cockles as second intermediate host. For six of them, metacercariae abundance per individual was 2 to 12 folds higher in B. minimus-infected cockles, exacerbating the potential negative impact on host. From the parasite point of view, metacercariae can be considered as hitchhikers, taking advantage of the abnormal migration of B. minimus-infected cockles to the sediment surface where they become more vulnerable to predators that are also the final hosts of many of these parasites.
(Parasitology Research. vol. 114, n° 0932-0113, pp. 1263-1278, 15/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Etude de l'impact des contaminants métalliques et organiques chez l'anguille européenne (Anguilla anguilla) et américaine (Anguilla rostrata) au moyen d'approches transcriptomiques
En milieu naturel, évaluer l’effet des contaminants sur les organismes aquatiques s’avère difficile dû aux nombreux facteurs (température, oxygénation, prédation, parasitisme, …) agissant sur les organismes. Le but de ces travaux de thèse était alors de tester la possibilité de détecter et hiérarchiser les effets de divers facteurs naturels et anthropiques sur des individus prélevés in situ. Le modèle d’étude utilisé était l’anguille Européenne (Anguilla anguilla) et Américaine (Anguilla rostrata). Pour appréhender les effets in situ des polluants, nous avons tenté d’identifier des gènes pour lesquels le niveau de transcription était spécifiquement corrélé à un polluant ou un facteur naturel mesuré sur le terrain au moyen de deux outils transcriptomiques : le séquençage haut débit et la puce à ADN. Les profils transcriptomiques obtenus à partir des foies d’anguilles directement prélevées sur le terrain ont été comparés dans un deuxième temps, à ceux obtenus à partir d’individus exposés au laboratoire à divers facteurs naturels et anthropiques de façon séparée. La comparaison de ces profils a montré une différence notable des réponses des individus exposés en laboratoire et ceux prélevés in situ, soulevant un effet non négligeable du stress induit par la captivité en mésocosme. La réalisation d’une étude similaire en utilisant la nageoire caudale comme méthode non invasive s’est révélée pertinente dans la capacité de cet organe à discriminer les différentes conditions expérimentales et de terrain. L’utilisation de la puce sur des gonades d’anguilles européennes maturées artificiellement a indiqué que la pollution pourrait affecter les capacités de reproduction des futurs géniteurs et contribuer alors au déclin massif de cette espèce observé depuis les dernières décennies.
(10/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Anobothrus amourouxi sp. nov., a new species of Ampharetidae (Polychaeta) from the Capbreton Canyon (Bay of Biscay, NE Atlantic Ocean)
A new species of Ampharetidae, Anobothrus amourouxi sp. nov., has been identified from bathyal depths of the Capbreton Canyon, Bay of Biscay (NE Atlantic Ocean). This new species is characterized by inner branchiae with transversal ciliated ridges, notochaetae from modified eighth thoracic unciniger with hirsute tips, uncini from thoracic unciniger with 6–7 teeth in lateral view arranged in two vertical rows in frontal view, fused segments II + III with paleae from SII and reduced notopodia without chaetae from SIII. An identification key for all hitherto described species of the genus Anobothrus is provided.
(Journal of the Marine Biological Association of the United Kingdom. vol. 95, n° 0025-3154, pp. 961-969, 09/02/2015)
LECOB, OOB, UPMC, CNRS, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Approche intégrée des conditions physico-chimiques affectant les cortèges biologiques de la partie fluviale de l'estuaire de la Gironde
Les estuaires, situés à l’interface entre les domaines continental et marin, constituent des zones essentielles dans les échanges de matières. Ils jouent dès lors un rôle capital pour les cycles biogéochimiques et biologiques et subissent, par ailleurs, des pressions climatiques et anthropiques croissantes depuis plusieurs décennies. Le présent travail a été focalisé sur les peuplements benthiques et pélagiques présents dans la partie fluviale (Garonne et Dordogne) de l’estuaire de la Gironde, zone àtrès faible salinité où ces peuplements n’avaient encore jamais été étudiés. Alors que la méiofaune, composée principalement de Nématodes, s’est avérée relativement abondante dans les domaines intertidal et subtidal, le macrobenthos est apparu composé essentiellement d’Oligochètes en intertidal et complètement absent en subtidal. La grande plasticité du copépode dominant Eurytemora affinis a été confirmée, celui-ci occupant une niche écologique différente dans la partie fluviale de l’estuaire par rapport à la zone haline. L’importance de la température plutôt que la qualité du pool nutritif sur la productivité d’E. affinis a été démontrée, mettant en évidence une fois de plus la grande adaptabilité de cette espèce dans un habitat très fluctuant. L’étude de l’habitat benthique et pélagique, notamment en terme de qualité du pool nutritif disponible pour les organismes, a démontré que la contribution de la matière organique réfractaire d’origine terrestre est dominante. La contribution du micro phytobenthos à la composition de la matière organique sédimentaire et pélagique a aussi été mise en évidence. Enfin,l’étude des communautés planctoniques dans la partie fluviale de l’estuaire de la Gironde a montré que l’espèce E. affinis y occupe une position clef.
(04/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Exposures of zebrafish through diet to three environmentally relevant mixtures of PAHs produce behavioral disruptions in unexposed F1 and F2 descendant.
The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades. PAHs are hydrophobic molecules which can accumulate in high concentrations in sediments acting then as major secondary sources. Fish contamination can occur through contact or residence nearby sediments or though dietary exposure. In this study, we analyzed certain physiological traits in unexposed fish (F1) issued from parents (F0) exposed through diet to three PAH mixtures at similar and environmentally relevant concentrations but differing in their compositions. For each mixture, no morphological differences were observed between concentrations. An increase in locomotor activity was observed in larvae issued from fish exposed to the highest concentration of a pyrolytic (PY) mixture. On the contrary, a decrease in locomotor activity was observed in larvae issued from heavy oil mixture (HO). In the case of the third mixture, light oil (LO), a reduction of the diurnal activity was observed during the setup of larval activity. Behavioral disruptions persisted in F1-PY juveniles and in their offspring (F2). Endocrine disruption was analyzed using cyp19a1b:GFP transgenic line and revealed disruptions in PY and LO offspring. Since no PAH metabolites were dosed in larvae, these findings suggest possible underlying mechanisms such as altered parental signaling molecule and/or hormone transferred in the gametes, eventually leading to early imprinting. Taken together, these results indicate that physiological disruptions are observed in offspring of fish exposed to PAH mixtures through diet.
(Environmental Science and Pollution Research. vol. 22, n° 0944-1344, pp. 16371–16383, 03/02/2015)
BE, IFREMER, LRHBL, HMMN, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INERIS, Irset, UA, UR, EHESP, INSERM, Biosit : Biologie - Santé - Innovation Technologique, IMB Sinica, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique
Disentangling direct and indirect effects of a legume shrub on its understorey community
Direct and indirect interactions among plants contribute to shape community composition through above- and belowground processes. However, we have not disentangled yet the direct and indirect soil and canopy effects of dominants on understorey species. We addressed this issue in a semi-arid system from southeast Spain dominated by the legume shrub Retama sphaerocarpa. During a year with an exceptionally dry spring, we removed the shrub canopy to quantify aboveground effects and compared removed-canopy plots to open plots between shrubs to quantify soil effects, both with and without watering. We added a grass removal treatment in order to separate direct from indirect shrub effects and quantified biomass, abundance, richness and composition of the forb functional group. With watering, changes in forb biomass were primarily driven by indirect shrub effects, with contrasting negative soil and positive aboveground indirect effects; changes in forb abundance and composition were more influenced by direct shrub soil effects with contrasting species composition between open and Retama patches. As community composition was different between open and Retama patches the indirect effects of Retama on forb species did not concern forbs from the open community but forbs from Retama patches. Indirect effects are, thus, important at the functional group level rather than at the species level. Without watering, there were no significant interactions. Changes in species richness between treatments were weak and seldom significant. We conclude that shrub effects on understorey forbs are primarily due to their influence on soil properties, directly affecting forb species composition but indirectly affecting the biomass of the forbs of the Retama patches, and only with sufficient water.
(Oikos. vol. 124, n° 0030-1299, pp. 1251-1262, 01/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Cockle infection by Himasthla quissetensis – I. From cercariae emergence to metacercariae infection
The European cockle (Cerastoderma edule) is an exploited bivalve along the North-Eastern Atlantic semi-sheltered ecosystems. Its population dynamics are driven by numerous environmental factors, including parasitism, particularly by trematodes. The complex life cycle of trematodes includes a free living stage (cercaria) between the first (a mollusk) and the second (an invertebrate or a vertebrate) intermediate hosts. Taking the example of Himasthla quissetensis, a dominant trematode in Arcachon Bay (France) utilizing Nassarius reticulatus as first intermediate host and the cockle as second intermediate host, we investigated the correlation between cockle infection and cercariae emergence by N. reticulatus, including the role of water temperature and light. Experimental and field data provided evidence that cercariae emergence from N. reticulatus took place during the night and for water temperature comprised between 15 °C and 22 °C (optimum at 20 °C). The lifespan of cercariae did not exceed 48 h and 50% of them were no more infectious after 7 h. A model was designed (emergence = f(water temperature)) in order to calculate an average monthly cercarial emergence rate according to water temperature that was daily recorded for 5 years (1998–2002). Concomitantly, non-infected cockles were transplanted each of these years in order to assess the infection rate by H. quissetensis. Infection occurred strictly for the same water temperatures (and dates) as those expected for cercariae emergence. Within each year, there was often (but not always) a good correlation between the predicted number of emerging cercariae and the observed number of cercariae transformed into metacercariae in cockles. However, the among-years variability of cockle infection (× 4.4 range) was not explained by the predicted annual number of emerging cercariae. This study highlights the importance of water temperature and light in stimulating cercariae emergence which is closely related to the occurrence of cockle infection. Accordingly, climate change would be expected to alter certain parasite transmission traits. Conversely, the lack of correlation between the total number of metacercariae in cockles and the expected number of cercariae suggests that other factors contribute to infestation variability.
(Journal of Sea Research (JSR), n° 1385-1101, 01/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS