Réponses d'un poisson estuarien, le flet (Platichthys flesus), au stress pesticides en milieu expérimental et au multi-stress in situ

Les estuaires sont impactés par les activités humaines et présentent une contamination chronique (métaux lourds, HAP, PCB, pesticides...) qui s ajoute aux stress biotiques et abiotiques inhérents au milieu estuarien. En privilégiant une approche intégrée du niveau moléculaire au niveau populationnel, cette thèse vise à appréhender les mécanismes de réponses du flet Platichthys flesus au stress chimique et au multi-stress. Une contamination expérimentale à deux mélanges d herbicides souligne tout d abord l expression de marqueurs moléculaires d atteinte hépatique (BHMT, alpha2M, Chemotaxine). Aucune perturbation de l homéostasie sanguine ou du statut nutritionnel n est cependant détectée chez les poissons exposés, suggérant un délai entre les réponses moléculaires et des réponses plus intégrées. La deuxième partie de ce travail sur les réponses biologiques de flets adultes au stress chimique souligne des teneurs en PCB, 10HP, Cu, Pb et Cd plus élevées dans la Gironde, la Loire et la Vilaine, ainsi qu un taux de croissance réduit et une faible expression de transcrits impliqués dans le métabolisme énergétique comparativement à l estuaire du Ster, suggérant un impact du stress chimique sur les populations de flets. Finalement, le suivi sur 6 mois des réponses biologiques de juvéniles sur la Vilaine montre une augmentation de la génotoxicité, de l expression de gènes impliqués dans le métabolisme énergétique (ATPase) et la détoxication (BHMT) avec la durée d exposition au stress. L évolution des fréquences alléliques des flets de la Vilaine converge vers celles de la Seine, suggérant ainsi une pression sélective exercée par le multi-stress au cours du vieillissement.Estuaries are impacted by human activities and are submitted to chronic contamination (heavy metals, PAHs, PCBs, pesticides...), which is added to biotic and abiotic stresses inherent to estuarine environment. By favouring an integrative approach from the molecular to the population level, this thesis aims at understanding the response mechanisms of the flounder Platichthys flesus to chemical stress and multi-stress. An experimental contamination to two herbicide mixtures first underlines the expression of molecular markers of liver injury (BHMT, alpha2M, chemotaxin). Neither disruption of blood homeostasis nor nutritional status is detected in exposed flounders, suggesting a delay between molecular responses and more integrated responses. The second part of this work dealing with biological responses of adult flounders to chemical stress underlines higher PCB, 10HP, Cu, Pb and Cd levels in Gironde, Loire and Vilaine, as well as lower growth rate and smaller expression of transcripts involved in energetic metabolism than in Ster estuary, suggesting an impact of chemical stress on flounders populations. Finally, the six-month survey of biolological responses of juvenile flounders on Vilaine shows an increase in genotoxicity, in expression of genes involved in energetic metabolism (ATPase) and detoxification (BHMT) with the duration of stress exposition. The allelic frequency evolution of flounders from Vilaine converges towards those of Seine estuary, suggesting a selective pressure induced by the multi-stress during the ageing.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

D7.12. 2nd user workshop report

<p>Report on the 7th Argo Science Workshop, organised jointly with Argo international</p&gt

Responses of juvenile European flounder (Platichthys flesus) to multistress in the Vilaine estuary, during a 6-month survey

International audiencePhysiological and genetic responses of age 0+ Platichthys flesus were investigated in the eutrophicated and moderately contaminated Vilaine estuary, during a 6-month survey. The main objective of this study was to explore the biological responses of fishes during their juvenile period in an estuarine system in order to detect a possible selective pressure induced by the environmental stress. Our results showed a general convergence in physiological responses along the survey: an increase in genotoxicity was associated with an increase in mRNA expression of ATPase and betaine homocysteine methyltransferase. These results could suggest an increase of cellular damage, energetic request, and detoxification rate related to the growing exposure time to stress. Considering the aging of the cohort, the genetic characteristics of the Vilaine flounder cohort came closer to the one observed in a highly stressed system, the Seine estuary, suggesting a potential selective pressure mainly induced by the chemical stress

Impacts of mixtures of herbicides on molecular and physiological responses of the European flounder Platichthys flesus

International audienceThe widespread use of pesticides results in a growing contamination of the aquatic environment. The effects of (1) a simple mixture of a glyphosate-based formulation and AMPA (Aminomethylphosphonic acid -- a primary metabolite of glyphosate) and of (2) a more complex mixture of herbicides (glyphosate/AMPA/mecoprop/acetochlor/2,4D) were explored on the molecular and physiological responses of the European flounder Platichthys flesus, considering a long-term and environmentally realistic contamination. Molecular responses were identified using suppression subtractive hybridization on liver samples: the level of gene transcription was significantly different between contaminated fishes vs control ones for 532 sequences, after a 62-day contamination. Among them, 222 sequences were identified by homology with data-based sequences; they encoded several metabolic pathways including: methionine and lipid metabolism, immunity, protein regulation, coagulation and energetic metabolism. Expression pattern of nine transcripts in the liver was confirmed by real-time PCR. The molecular study underlined that potential markers of liver injury were expressed for both mixtures, in particular betaine homocysteine methyl transferase and chemotaxin. Physiological responses were analysed considering blood parameters and condition factor; after the two months contamination period; no significant physiological difference was detected between contaminated and control fish

Responses of the European flounder Platichthys flesus to the chemical stress in estuaries: load of contaminants, gene expression, cellular impact and growth rate

International audienceEuropean flounder responses to the chemical stress were assessed by a comparative approach on four estuaries displaying contrasted patterns of contamination. The contamination typology of the estuaries was investigated by individual measurements of contaminants in fish. Molecular and physiological responses were studied by gene expression, genotoxicity, neurotoxicity and growth rate. Fishes in contaminated estuaries were characterized by high levels of bioaccumulated contaminants, slow energetic metabolism and reduced growth rate, in contrast to the fish responses in the reference site. A seasonal effect was highlighted for contaminated flounder populations, with high PCB levels, high genotoxicity and elevated detoxification rate in summer compared with winter

Variation patterns in individual fish responses to chemical stress among estuaries, seasons and genders: the case of the European flounder (Platichthys flesus) in the Bay of Biscay

International audienceThe objective was to describe and model varia- tion patterns in individual fish responses to contaminants among estuaries, season and gender. Two hundred twenty- seven adult European flounders were collected in two sea- sons (winter and summer) in four estuaries along the Bay of Biscay (South West France), focusing on a pristine system (the Ster), vs. three estuaries displaying contrasted levels of contaminants (the Vilaine, Loire and Gironde). Twenty-three variables were measured by fish, considering the load of contaminants (liver metals, liver and muscle persistent organic pollutants, muscle polycyclic aromatic hydrocar- bons); the gene expression (Cyt C oxydase, ATPase, BHMT, Cyt P450 1A1, ferritin); the blood genotoxicity (Comet test); and liver histology (foci of cellular alteration-tumour, steatosis, inflammation, abnormal glycogen storage). Ca- nonical redundancy analysis (RDA) was used to model these variables using gender, season and estuary of origin as explanatory variables. The results underlined the homo- geneity of fish responses within the pristine site (Ster) and more important seasonal variability within the three contam- inated systems. The complete model RDA was significant and explained 35 % of total variance. Estuary and season respectively explained 30 and 5 % of the total independent variation components, whilst gender was not a significant factor. The first axis of the RDA explains nearly 27 % of the total variance and mostly represents a gradient of contami- nation. The links between the load of contaminants, the expression of several genes and the biomarkers were ana- lysed considering different levels of chemical stress and a possible multi-stress, particularly in the Vilaine estuary