Effets de contaminations d'embryons et d'adultes de poissons zèbres (Danio rerio) par des PCB et des HAP

Aquatic environments are ultimate reservoir for many persistent organic pollutants, including polychlorinatedbiphenyls (PCBs, bioaccumulative compounds) and polycyclic aromatic hydrocarbons (PAHs, compoundsaccumulated in the sediment and metabolized by vertebrates). Fish can be exposed to these pollutants at different life stages which can alter their functional integrity. The objectives of this PhD were to assess physiological alterations following exposure to mixtures representative of environmental situations. Thus, on the one hand,juvenile and adult zebrafish were exposed through the trophic pathway to PCB mixture representative of European Estuaries. The results showed that bioaccumulation varied with the congeners as well as transfer to eggs and for the latter, the level of chlorination is decisive. Impaired reproduction characterized by a reduction in the rate of fertilization and the appearance of a massive follicular atresia were shown. This work could be completed 1) at the molecular level to better understand the underlying mechanisms including endocrine disruptive activity and 2) by the evaluation of effects at the population level by a modelling approach. On the other hand, embryos were exposed for 96 h to sediment spiked with individual PAHs. The obtained phenotypes were consistent with the effects described for these PAHs and thus validated the exposure process. This procedure could be used to assess the toxicity of natural sediment after extraction of the aromatic fraction as well as to assess the toxicity of hydrophobic molecules. To be reliable tests, it remains essential to identify early markers of late effects to avoid under estimating the toxicity of a compound.Les milieux aquatiques constituent des réservoirs ultimes pour de nombreux polluants organiques persistants,notamment les polychlorobiphényles (PCB, composés bioaccumulables) et les hydrocarbures aromatiques polycycliques (HAP, composés accumulés dans le sédiment et métabolisés par les vertébrés). Les poissons peuvent être exposés à ces polluants à plusieurs stades de vie, ce qui peut altérer leur intégrité fonctionnelle. Les objectifs de cette thèse étaient d'évaluer les altérations physiologiques entrainées par des expositions représentatives de situations environnementales. Ainsi, d’une part, des juvéniles et adultes de poissons zèbres ont été exposés par voie trophique à des mélanges de PCB représentatifs des estuaires européens. Les résultats montrent que la bioaccumulation varie en fonction des congénères de même que le transfert vers les oeufs, et pour ce dernier, le niveau de substitution par des chlores est déterminant. Une altération de la reproduction caractérisée par une réduction du taux de fécondation et l'apparition d'une atrésie folliculaire massive ont été montrées. Ces travaux pourraient être complétés 1) au niveau moléculaire pour mieux comprendre les mécanismes sous-jacents et notamment l'activité perturbateur endocrinien et 2) par l'évaluation des effets au niveau des populations par une approche de modélisation. D’autre part, des embryons ont été exposés pendant 96h à des sédiments enrobés par des HAP individuels. Les phénotypes obtenus sont conformes aux effets décrits pour ces HAP et ont permis de valider la procédure d'exposition. Cette procédure pourrait être utilisée pour évaluer la toxicité de sédiments naturels après extraction de la fraction aromatique, ainsi que pour évaluer la toxicité de molécules hydrophobes. Pour être fiable dans le cadre de tests, il reste indispensable d'identifier des marqueurs précoces d'effets tardifs pour éviter de sous-estimer la toxicité d'un composé

Effects of zebrafish (Danio rerio) embryos and adults contaminations with PCB and PAH

Les milieux aquatiques constituent des réservoirs ultimes pour de nombreux polluants organiques persistants,notamment les polychlorobiphényles (PCB, composés bioaccumulables) et les hydrocarbures aromatiques polycycliques (HAP, composés accumulés dans le sédiment et métabolisés par les vertébrés). Les poissons peuvent être exposés à ces polluants à plusieurs stades de vie, ce qui peut altérer leur intégrité fonctionnelle. Les objectifs de cette thèse étaient d'évaluer les altérations physiologiques entrainées par des expositions représentatives de situations environnementales. Ainsi, d’une part, des juvéniles et adultes de poissons zèbres ont été exposés par voie trophique à des mélanges de PCB représentatifs des estuaires européens. Les résultats montrent que la bioaccumulation varie en fonction des congénères de même que le transfert vers les oeufs, et pour ce dernier, le niveau de substitution par des chlores est déterminant. Une altération de la reproduction caractérisée par une réduction du taux de fécondation et l'apparition d'une atrésie folliculaire massive ont été montrées. Ces travaux pourraient être complétés 1) au niveau moléculaire pour mieux comprendre les mécanismes sous-jacents et notamment l'activité perturbateur endocrinien et 2) par l'évaluation des effets au niveau des populations par une approche de modélisation. D’autre part, des embryons ont été exposés pendant 96h à des sédiments enrobés par des HAP individuels. Les phénotypes obtenus sont conformes aux effets décrits pour ces HAP et ont permis de valider la procédure d'exposition. Cette procédure pourrait être utilisée pour évaluer la toxicité de sédiments naturels après extraction de la fraction aromatique, ainsi que pour évaluer la toxicité de molécules hydrophobes. Pour être fiable dans le cadre de tests, il reste indispensable d'identifier des marqueurs précoces d'effets tardifs pour éviter de sous-estimer la toxicité d'un composé.Aquatic environments are ultimate reservoir for many persistent organic pollutants, including polychlorinatedbiphenyls (PCBs, bioaccumulative compounds) and polycyclic aromatic hydrocarbons (PAHs, compoundsaccumulated in the sediment and metabolized by vertebrates). Fish can be exposed to these pollutants at different life stages which can alter their functional integrity. The objectives of this PhD were to assess physiological alterations following exposure to mixtures representative of environmental situations. Thus, on the one hand,juvenile and adult zebrafish were exposed through the trophic pathway to PCB mixture representative of European Estuaries. The results showed that bioaccumulation varied with the congeners as well as transfer to eggs and for the latter, the level of chlorination is decisive. Impaired reproduction characterized by a reduction in the rate of fertilization and the appearance of a massive follicular atresia were shown. This work could be completed 1) at the molecular level to better understand the underlying mechanisms including endocrine disruptive activity and 2) by the evaluation of effects at the population level by a modelling approach. On the other hand, embryos were exposed for 96 h to sediment spiked with individual PAHs. The obtained phenotypes were consistent with the effects described for these PAHs and thus validated the exposure process. This procedure could be used to assess the toxicity of natural sediment after extraction of the aromatic fraction as well as to assess the toxicity of hydrophobic molecules. To be reliable tests, it remains essential to identify early markers of late effects to avoid under estimating the toxicity of a compound

Long-term food-exposure of zebrafish to PCB mixtures mimicking some environmental situations induces ovary pathology and impairs reproduction ability

Although the use of polychlorinated biphenyls (PCBs) has been banned for several decades, they are still present in the environment and are occasionally mechanically released from sediment or transferred through the trophic chain. Field analyses have established correlations between exposure to PCBs and alterations in fish physiology including reproductive function. Experimental exposures have been mainly performed using dioxin-like PCBs or other congeners at very high concentrations. However, these studies are often difficult to relate to real-life conditions. In the present study, we performed a life-cycle exposure using zebrafish model and mixtures representative of some environmental situations in terms of doses, composition and containing mainly non dioxin-like congeners. Exposure was performed through diet which is the main contamination route in the field. We demonstrated a bioaccumulation of PCBs in males and females as well as a maternal transfer to the eggs. Survival, growth and organ size were similar for all conditions. Several reproductive traits were altered after exposure to a PCB-contaminated diet, including a reduction in the number of fertilized eggs per spawn as well as an increase of the number of poorly fertilized spawns. This latter observation was found irrespective of the sex of contaminated fish. This is related to modifications of ovary histology revealing a decrease of maturing follicles and an increase of atretic follicles in the ovaries of females exposed to PCBs. These results indicate that exposure to PCBs mixtures mimicking some environmental situations, including mainly non dioxin-like congeners, can lead to a dramatic reduction in the number of offspring produced by a female over a lifetime. This is of great concern for wild species living under natural conditions. (C) 2011 Elsevier B.V. All rights reserved

Long-term dietary-exposure to non-coplanar PCBs induces behavioral disruptions in adult zebrafish and their offspring

The use of polychlorinated biphenyls (PCBs) has been banned for several decades. PCBs have a long biological half-life and high liposolubility which leads to their bioaccumulation and biomagnification through food chains over a wide range of trophic levels. Exposure can lead to changes in animal physiology and behavior and has been demonstrated in both experimental and field analyses. There are also potential risks to high trophic level predators, including humans. A maternal transfer has been demonstrated in fish as PCBs bind to lipids in eggs. In this study, behavioral traits (exploration and free swimming, with or without challenges) of contaminated zebrafish (Danio rerio) adults and their offspring (both as five-day-old larvae and as two-month-old fish reared under standard conditions) were measured using video-tracking. Long-term dietary exposure to a mixture of non-coplanar PCBs was used to mimic known environmental contamination levels and congener composition. Eight-week-old fish were exposed for eight months at 26-28 degrees C. Those exposed to an intermediate dose (equivalent to that found in the Loire Estuary, Sigma(CB) = 515 ng g(-1) dry weight in food) displayed behavioral disruption in exploration capacities. Fish exposed to the highest dose (equivalent to that found in the Seine Estuary, Sigma(CB) = 2302 ng g(-1), dry weight in food) displayed an increased swimming activity at the end of the night. In offspring, larval activity was increased and two-month-old fish occupied the bottom section of the tank less often. These findings call for more long-term experiments using the zebrafish model; the mechanisms underlying behavioral disruptions need to be understood due to their implications for both human health and their ecological relevance in terms of individual fitness and survival

From model to fisheries species: Behavioural studies to reveal the potential effects of contaminant on fish population

No abstracts are to be cited without prior reference to the author.Because organic pollutants are stable and are found throughout the natural environment, their effects on animal physiology or their dynamics within trophic networks have been studied for many years. However, behavioural studies are rarely used in ecotoxicology although these have the potential to reveal compensation mechanisms and therefore provide a link between individual behaviours and population characteristics. The aim of our study was to identify relevant behavioural indicators affected by PCB contaminants in two fish species, the common sole (Solea solea) and the zebrafish (Danio rerio). Juvenile fish were exposed through diet to two environmental concentrations of PCBs and different behavioural traits were compared with those of control fish. For each species, we studied: (i) exploratory behaviour in a T-maze, (ii) 24-h swimming activity, (iii) background colour preference and (iv) group dispersion. Because of ecological differences between the two species, we also examined: (v) cryptic and burying capacities in sole and (vi) larvae locomotory activity of zebrafish. State-of-the-art full-automatic behavioural analyses using Ethovision video tracking solution (Noldus, The Netherlands) to analyse swimming activity measures (e.g. velocity, mobility, distance travelled) was combined with semi-automatic analysis (e.g. interindividual distances, spatial distribution, behaviour quantification) to obtain a wider range of potential behavioural variables. Infrared lighting with dedicated sensitive cameras was also used to study fish and larvae both in the light and in the dark. The differential responses and the relevance of the variable responses observed are discussed in the context of the ecological requirements of fish

Génération POP – Effets d’une exposition précoce d’embryons de poissons aux polluants organiques persistants et conséquences sur la population

International audienc

Génération POP – Effets d’une exposition précoce d’embryons de poissons aux polluants organiques persistants et conséquences sur la population

International audienc