Études de biomarqueurs chez la mye commune (Mya arenaria) du fjord du Saguenay : bilan de recherches (1997 à 2006)

Cet écrit se veut une synthèse des principales trouvailles afférentes aux études de terrain conduites annuellement de 1997 à 2006 en zones intertidales du fjord du Saguenay, et de celles situées autour de sa confluence avec l’estuaire du Saint-Laurent, dans le but de mieux comprendre les stress anthropiques auxquels est soumise la mye commune (Mya arenaria), bivalve ubiquiste de ces habitats sédimentaires. À l’aide d’une batterie variée de biomarqueurs, lesquels ont fait l’objet de mesures chez l’animal entier, certains de ses tissus ou cellules, nous avons pu mettre en évidence divers effets écotoxiques qui sont vraisemblablement imputables aux sources (urbaines, industrielles, portuaires, diffuses ou atmosphériques) de contamination chimique impactant le Saguenay. Dépendant du site et de ses caractéristiques pollutionnelles, nous avons noté des dérèglements de santé chez la mye qui incluent des effets sur son système reproducteur (divers types de perturbation endocrine associés aux substances estrogéniques, aux métaux ou aux TBT), sur son système immunitaire (stimulation ou dépression d’immunocompétence jaugée par la capacité de phagocytose d’hémocytes), ainsi que des effets cumulatifs de polluants qui se traduisent par des réponses, à la hausse ou à la baisse, de biomarqueurs de défenses (e.g., métallothionéines, CYP1A1, glutathione S-transférases), de dommages (e.g., augmentation de brins d’ADN, augmentation de l’activité de cyclo-oxygénase témoignant d’inflammation, peroxydation des lipides) et morphologiques (e.g., inhibition de croissance, baisse d’indice gonado-somatique). Nous démontrons aussi une plus grande dépense en énergie au niveau mitochondrial (transport d’électrons mitochondrial dans la gonade ou glande digestive) chez les myes de zones impactées, laquelle semble pouvoir être exacerbée en conditions de stress thermiques que laissent présager les changements climatiques à venir. Au final, ce bilan d’études de biomarqueurs confirme l’utilité du modèle bivalve Mya arenaria comme bio-indicateur de la qualité hydrique du Saguenay et il renseigne sur les divers affronts que subissent ces invertébrés dans ce milieu toujours aux prises avec des sources de contamination variées. D’autres études envisagées affineront nos connaissances au sujet des risques cumulatifs liés à la contamination chimique du fjord.This paper presents the major findings of annual field outings conducted from 1997 to 2006 in Saguenay Fjord intertidal areas as well as those located in proximity with the St. Lawrence River estuary. Study objectives sought to enhance our understanding of pollution pressures incurred on the soft shell clam, Mya arenaria, endemic to mud flats of these regions. By measuring the responses of a battery of biomarkers in whole animals, organs or cells, we demonstrated various adverse effects that are likely linked to chemical contamination sources (municipal, industrial, portuary, non point and atmospheric) intrinsic to the Saguenay area. Based on site and pollution features proper to each, health problems were observed in clams that included effects on their reproductive system (endocrine disruption events linked to estrogenic substances, metals or TBT), on their immune system (increase or decrease of immunocompetence assessed by phagocytic performance of hemocytes), as well as cumulative effects of pollutants, shown either by upward or downward responses of defense biomarkers ((e.g., metallothioneins, CYP1A1, glutathion S‑transferase), damage biomarkers (e.g., increase in DNA strand breaks, increase in inflammatory cyclo-oxygenase activity, lipid peroxidation) and metrics biomarkers (e.g., growth inhibition, lower gonado-somatic index). In pollution-impacted sites, clams further displayed a greater expenditure of mitochondrial energy (measured by mitochondrial electron transport in gonad or digestive gland), an energy loss that could possibly be augmented under thermic stress conditions linked to climate change. This long-term biomarker work establishes Mya arenaria as a useful bioindicator species to appraise Saguenay Fjord water quality as reflected by the diverse chemical insults to which these invertebrates are exposed in an ecosystem still struggling with multiple contamination inputs. Future studies should contribute to strengthen our knowledge related to cumulative risk issues linked to the fjord’s chemical pollution

Qu’en est-il de l’état de santé des myes au Saguenay ? Un bilan d’études sur plus d’une décennie

Le fjord du Saguenay, reconnu pour sa faune diversifiée mais aussi pour la contamination reliée aux activités industrielles et anthropiques, a fait l’objet d’un vaste programme de suivi environnemental, entrepris par notre équipe et qui visait à répondre à la question fondamentale : L’état de santé des myes s’est-il modifié dans le fjord du Saguenay ? Dans cet article de synthèse, nous avons regroupé des résultats déjà publiés sur la condition physiologique de Mya arenaria ainsi que des résultats originaux pour extraire des tendances, de façon à répertorier les sites qui s’avèrent critiques pour le bien-être physiologique de la mye. Mya arenaria (LINNÉ, 1758) ou mye des sables, choisie comme espèce sentinelle, a été échantillonnée de 1994 à 2007, en période de maturité sexuelle, dans des sites situés à l’intérieur du fjord et à son embouchure. Les objectifs de cet article sont de comparer les résultats de différents indices de condition et de suivis hormonaux et de la gamétogenèse de chaque site et en fonction des sexes, pour identifier les sites moins favorables pour la croissance et la reproduction de la mye. Nous avons démontré que les myes de Baie‑Sainte-Catherine subissent des retards de gamétogenèse tandis que les niveaux d’hormones stéroïdiennes sont très bas à Tadoussac. Ces deux sites sont soumis à des influences portuaires et à la circulation navale. Le site de Baie‑Éternité, plus en amont, se caractérise par des influences portuaires (huiles et peintures antisalissures) et une forte contamination métallique de sources urbaines et terrigènes. Anse‑aux‑Érables est un site près des influences industrielles, tandis que Anse‑Saint‑Jean est fortement influencée par les effluents municipaux et domestiques. D’amont en aval sur la rivière Saguenay, les myes des sites Anse‑à‑la‑Croix, Anse‑aux‑Érables, Petit‑Saguenay, Anse‑à‑la‑Barque, Tadoussac et Pointe‑aux‑Alouettes ont montré une croissance moindre. Les sites de Baie‑Éternité, Anse‑aux‑Érables, Anse‑Saint‑Jean et Baie-Sainte-Catherine ont un indice de maturité sexuelle moindre qu’aux autres sites, les données regroupées démontrant que ce sont les sites les plus influencés dans le fjord du Saguenay, résultats corroborés par les résultats de phagocytose. Toutes ces données démontrent que l’état physiologique de la mye répond à différents facteurs, anthropiques, biotiques et abiotiques, et que les sources ponctuelles de contamination viennent renforcer les effets négatifs de paramètres abiotiques telles la température et les conditions trophiques.The Saguenay fjord has been submitted for many years to anthropogenic influences. We surveyed this ecosystem between 1994 and 2007 to assess if Mya arenaria health status was altered by the contamination present in this ecosystem. The physiological condition of clams was determined using grouped annual data from sites at the mouth and in the Saguenay fjord. The results were analyzed according to sex and sites for all the samplings done during the active gametogenesis. The aims of this paper are to compare results of condition signs, gametogenesis stages and hormonal levels between sites and according to sex, to finally identify which sites were less favorable for the growth and reproduction of clams. We have shown that clams from Baie-Sainte-Catherine had delayed gametogenesis while those from Tadoussac showed very low steroid hormonal levels. Portuary and naval circulation influences could explain these particular results that also correspond to those from phagocytosis. Upstream in Baie‑Éternité, portuary influences (oils, anti-fouling paints) and metallic inputs from urban and terrigenous sources were reported. In Anse-aux-Érables, metallic contamination comes from industrial sources, while Anse-Saint‑Jean is influenced by sewage discharges from domestic and urban origin. From upstream to downstream, clams from Anse‑à‑la‑Croix, Anse‑aux‑Érables, Petit‑Saguenay, Anse‑à‑la‑Barque, Tadoussac and Pointe‑aux‑Alouettes showed decreased growth. Baie‑Éternité, Anse‑aux‑Érables, Anse‑Saint‑Jean and Baie-Sainte-Catherine sites, with their lower sexual maturity index and decreased phagocytosis, were shown to be the more influenced by contamination. All these data show that physiological condition of Mya arenaria reflects the combined effects of abiotic factors such as contamination, trophic conditions and site characteristics

Oxidative stress and immunologic responses following a dietary exposure to PAHs in Mya arenaria

<p>Abstract</p> <p>Background</p> <p>The aim of this research was to investigate oxidative stress and immune responses following a dietary polycyclic aromatic hydrocarbon (PAH) exposure in a marine bioindicator organism, the soft shell clam, <it>Mya arenaria</it>. Immune parameters in hemolymph (haemocyte number, efficiency of phagocytosis and haemocyte activity) and assessment of oxidative stress using catalase (CAT) activity and levels of malondialdehyde (MDA) performed on the digestive gland were estimated as biomarkers in clams fed in mesocosm with PAH contaminated phytoplankton. MDA levels and CAT activities were also measured <it>in situ </it>in organisms sampled in a control site (Metis Beach, Québec, Canada) as well as organisms sampled in a site receiving domestic effluents (Pointe-au-Père, Québec, Canada), to assess effects of abiotic variables related to seasonal variations and mixed contamination on the selected parameters.</p> <p>Results</p> <p>Results on immune parameters suggest that the PAHs may interfere with the maturation and/or differentiation processes of haemocytes. MDA results showed that lipid peroxidation did not occur following the exposure. The levels of CAT activity corresponded to weak antioxidant activity (no significant differences). Recovery was noted for all the immune endpoints at the end of the experiment.</p> <p>Conclusion</p> <p>Results suggest that immune parameters are early biomarkers that can efficiently detect a physiological change during a short term exposure to low concentrations of PAHs. The <it>in situ </it>survey (in the natural environment) suggested that clams from the Pointe-au-Père site did not show any oxidative stress as well as the clams contaminated in mesocosm, probably due to the low concentrations of PAHs used for this study. MDA levels increased however in organisms from Metis Beach, a response probably related to domestic effluents or parasitism.</p

Exemple de coopération franco-québécoises : la réalisation d’un cours sur la pollution marine dans le cadre de l’agence universitaire francophone

Un cours virtuel (http://www3.uqar. uquebec.ca/jpellerin/seme/) a été conçu pour les francophones du monde entier et proposé avec différents cheminements pour des formations spécialisées ou finalisées. Le cours est composé de 20 modules couvrant les notions indispensables pour la compréhension de l’environnement marin, de la pollution marine et des outils de biosurveillance. Les chercheurs impliqués dans cette réalisation provenaient du Québec (J. Pellerin), de France (J.-C. Amiard), de Tunisie (P. Aïssa) et de Mauritanie (Z. Sidoumou). Nous avons profité de l’expérience de chacune des équipes en environnement (enseignement et recherche) pour concevoir des modules qui, par leurs exemples, mises en situation et études de cas, s’adaptent aux étudiants provenant de différentes cultures et subissant des problèmes environnementaux différents selon que leur pays soit en zone tempérée, subtropicale ou tropicale.Pellerin Jocelyne. Exemple de coopération franco-québécoises : la réalisation d’un cours sur la pollution marine dans le cadre de l’agence universitaire francophone. In: Échanges scientifiques et techniques d’une rive atlantique à l’autre. Actes du 133e Congrès national des sociétés historiques et scientifiques, « Migrations, transferts et échanges de part et d’autre de l’Atlantique », Québec, 2008. Paris : Editions du CTHS, 2009. pp. 167-172. (Actes des congrès nationaux des sociétés historiques et scientifiques, 133-1

Activité vitellogénique et stéroïdienne chez Mya arenaria (mollusque bivalve) durant la gamétogenèse et en réponse à une exposition au 17ß-oestradiol

Mya arenaria est un bivalve marin endobenthique et ubiquiste. Les connaissances écophysiologiques sur les changements biochimiques relatifs à la gamétogenèse et l'implication des hormones stéroïdiennes dans le contrôle hormonal de cette dernière sont encore limitées chez cette espèce. Cette thèse de doctorat rapporte de nouvelles connaissances sur le processus vitellogénique et la présence d'hormones stéroïdiennes (testostérone et 17ß-œstradiol) dans la gonade des myes durant la gamétogenèse. L'accroissement du diamètre des ovocytes a permis de définir une séquence vitellogénique durant laquelle l'augmentation des concentrations en ADN et en ARN est significative et l'augmentation de la quantité de protéines de réserve (>400 kDa) est également effective. Les hormones stéroïdiennes apparaissent impliquées dans le contrôle hormonal de la gamétogenèse bien que leurs concentrations soient comparables chez les deux sexes et que leurs interactions avec les neurohormones restent à définir.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Multiple experimental approaches of immunotoxic effects of mercury chloride in the blue mussel, Mytilus edulis, through in vivo, in tubo and in vitro exposures

International audienceBiological impairments due to mercury discharge into the environment are now an issue of global concern. From the three forms of mercury found in aquatic ecosystems, the immunotoxic effects of mercury chloride were examined in the model animal, the blue mussel. In order to investigate the toxic potency of this chemical, three exposure regimes were carried out: chronic exposure of groups of individuals, a new protocol "in tubo" designed for sub-acute exposures of individuals, and acute exposures of target cells. Chronic exposure revealed significant immunotoxic effects after 7 days at 10−6 M, while acute exposures showed significant inhibition of phagocytosis at 10−4 M and 10−3 M. In sub-acute exposures both circulating haemocytes and haemocyte mortality increased at 10−4 M and 10−3 M while phagocytosis and the clearance rate drew hormetic toxic effects on healthy individuals. These results suggest the use of the "in tubo" design for bivalve toxicological individual studies

Relative potency of PCB126 to TCDD for sublethal embryotoxicity in the mummichog (Fundulus heteroclitus)

International audienceThe relative potency (ReP) of 3,3',4,4',5-pentachlorobiphenyl (PCB126) to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for sublethal responses was assessed in Fundulus heteroclitus embryos. Eggs were treated with intravitelline injections of graded sublethal doses of PCB126 (312-5000 pg g(-1) wet weight, ww) or TCDD (5-1280 pg g(-1) ww). At 16 days post-fertilization (DPF), craniofacial deformities were observed in larvae hatched from eggs treated with the two highest doses of PCB126 (2500-5000 pg g(-1) ww). Both compounds caused a dose-responsive reduction of larval growth and prey capture ability (at ≥1250 pg g(-1) ww), and induction of ethoxyresorufin-O-deethylase (EROD) activity (at ≥80 pg g(-1) ww). The dose-response relationships for EROD activity for PCB126 and TCDD had similar slopes and the ReP of PCB126 to TCDD for EROD activity was estimated at 0.71. This is 140-fold higher than the World Health Organization (WHO) TCDD equivalency factor (TEF) of PCB126 for fish (0.005), which is based on rainbow trout (Oncorhynchus mykiss) embryolethality data. The slope of the dose-response relationship for prey capture ability for PCB126 was steeper than for TCDD, suggesting different mechanisms of action. Expression levels of several genes were also studied by quantitative real-time polymerase chain reaction (qPCR) following exposure to single doses of TCDD or PCB126 (1280 and 1250 pg g(-1) ww, respectively) causing similar EROD induction. A different pattern of responses was observed between PCB126 and TCDD: PCB126 appeared to induce antioxidant responses by inducing sod2 expression, while TCDD did not. These results suggest that relative potencies are species-specific and that the current ReP for PCB126 underestimates its toxicity for some fish species. It is recommended to develop species-specific RePs for a variety of sublethal endpoints and at environmentally relevant doses

Physiological effects of temperature and a herbicide mixture on the soft-shell clam Mya arenaria (Mollusca, Bivalvia)

The aim of the current study was to investigate effects of temperature and a mixture of herbicides on the physiological status of the bivalve Mya arenaria. Bivalves acclimated to two temperatures (7 and 18°C) were exposed for 28 d to 0.01 mg/L of a pesticide formulation containing dichlorophenoxyacetic acid (2,4‐D), 2‐(2‐methyl‐4‐chlorophenoxy) propionic acid (mecoprop), and 3,6‐dichloro‐2‐methoxybenzoic acid (dicamba). At days 7, 14, and 28, mortality, immune parameters (hemocyte number, phagocytic activity, and efficiency), biomarkers of oxidative stress (catalase [CAT] and superoxide dismutase [SOD] activities and malondialdehyde [MDA] content), the metabolic enzyme cytochrome C oxidase (CCO), a biomarker of pesticide exposure (acetylcholinesterase [AChE]), and the activity of an enzyme related to gametogenesis (aspartate transcarbamylase [ATCase]) were monitored in clam tissues. Gonadosomatic index (GSI), condition factor (CF), and sex were also assessed. In clams acclimated to 7°C, exposure to pesticide enhanced CCO activity and CF and decreased MDA content, hemocyte number, CAT, and SOD activities. In clams kept at 18°C, pesticide effects appeared minor compared with samples kept at 7°C. In bivalves acclimated to 18°C, CCO, SOD, and ATCase activity and MDA content were enhanced, and hemocyte number, CAT, and AchE activities and phagocytosis were suppressed. In samples exposed to pesticides, increased temperature enhanced MDA content and CCO and SOD activity and suppressed hemocyte number and CAT and AchE activity. A gradual sexual maturation was observed in both sexes through experimental time, but females had a higher sensitivity to temperature and pesticides compared to males. Increased temperature altered the ability of the sentinel species Mya arenaria to respond to pesticide exposures. Further work is needed to understand the impacts of increasing temperature on the whole St. Lawrence estuary ecosystem

Sequence analysis of a normalized cDNA library of Mytilus edulis hemocytes exposed to Vibrio splendidus LGP32 strain

In the past decades, reports on bivalves' pathogens and associated mortalities have steadily increased. To face pathogenic micro-organisms, bivalves rely on innate defenses established in hemocytes which are essentially based on phagocytosis and cytotoxic reactions. As a step towards a better understanding of the molecular mechanisms involved in the mussel Mytilus edulis innate immune system, we constructed and sequenced a normalized cDNA library specific to M. edulis hemocytes unchallenged (control) and challenged with Vibrio splendidus LGP32 strain for 2, 4 and 6 h. A total of 1,024,708 nucleotide reads have been generated using 454 pyrosequencing. These reads have been assembled and annotated into 19,622 sequences which we believe cover most of the M. edulis hemocytes transcriptome. These sequences were successfully assigned to biological process, cellular component, and molecular function Gene Ontology (GO) categories. Several transcripts related to immunity and stress such as some fibrinogen related proteins and Toll-like receptors, the complement C1qDC, some antioxidant enzymes and antimicrobial peptides have already been identified. In addition, Toll-like receptors signaling pathways and the lysosome and apoptosis mechanisms were compared to KEGG reference pathways. As an attempt for large scale RNA sequencing, this study focuses on identifying and annotating transcripts from M. edulis hemocytes regulated during an in vitro experimental challenge with V. splendidus. The bioinformatic analysis provided a reference transcriptome, which could be used in studies aiming to quantify the level of transcripts using high-throughput analysis such as RNA-Seq