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Evaluation des effets chroniques du diclofénac sur un mollusque gastéropode avec des approches physiologiques, comportementales, transcriptomiques et métabolomiques

Abstract : Pharmaceuticals environmental contamination provoked an increase of concern over the past decade. Among these drugs, diclofenac (DCF) is one of the most consumed and identified in the aquatic environment. Multiple ecotoxicological studies have investigated these contaminant effects on marine and freshwater aquatic species, showing mostly a reproduction impact. However, only a few chronic studies at environmental concentrations has been conducted on aquatic invertebrates, and the molecular mechanisms involved in the effects that have been observed are poorly understood. This thesis aimed to assess DCF impact at environmental concentrations after a multigenerational exposure in the Lymnaea stagnalis freshwater gastropod. For this purpose, physiological, behavioral and molecular approaches were implemented. DCF biotransformation products formed in L. stagnalis after 3 and 7 days of exposure at 300 µg/L were explored. A multigenerational study was then conducted on 3 generations of snails exposed to 0.1, 2 and 10 µg/L DCF concentrations. This contaminant impact was explored on physiological (egg hatching, growth, reproduction) and behavioral (feeding, locomotion, light stress response) parameters. The parental generation exposed to 0.1 and 10 µg/L was analyzed molecularly at the adult stage on 2 organs (heads and reproductive apparatus). The DCF metabolism study in L. stagnalis snail revealed 19 DCF metabolites, 14 of which were phase I and 4 were phase II. Among these metabolites, 12 were observed for the first time in aquatic species. The major biotransformation pathway in this organism appeared to be hydroxylation, with 3 hydroxylated and 3 dihydroxylated identified metabolites. During the chronic DCF exposure, hatching was affected by DCF only in the F2 generation, with a faster egg hatching (10 µg/L). The juvenile growth was faster in the parental generation (F0) and in the F2 generation at all DCF concentrations, as well as in the F1 exposed to 0.1 µg/L. On the contrary, the growth was slower in the F1 exposed to 2 and 10 µg/L. The egg masses production was not impacted by the DCF exposure in the parental generation, while a lower number of eggs per egg mass was observed in the F1 (2 µg/L) and a higher number of egg masses was produced per snail in the F2 (10 µg/L). DCF lowered the feeding rate in the F0 juveniles (2 µg/L) and in the F1 adults (0.1 and 2 µg/L), whereas it increased it in the F2 adults (10 µg/L). DCF stimulated locomotor behavior in F1 individuals (2 and 10 µg/L). DCF did not affect the light stress response. The non-targeted molecular approaches (transcriptomic, metabolomics) conducted on the F0 adult snails suggested neurotoxicity, oxidative stress and immunity imbalance induction. Osmoregulation could be altered, as well as the energy metabolism and the reproduction. This potential impact of DCF on reproduction was not highlighted in the F0 generation reproduction test but was demonstrated on the offspring, thus confirming the molecular markers potential to be early effects indicators. All these results allow us to have a larger view of DCF chronic effects on the aquatic environment.
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Submitted on : Tuesday, July 5, 2022 - 6:05:12 PM
Last modification on : Wednesday, July 6, 2022 - 3:54:22 AM

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  • HAL Id : tel-03714705, version 1

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Lucie Bouly. Evaluation des effets chroniques du diclofénac sur un mollusque gastéropode avec des approches physiologiques, comportementales, transcriptomiques et métabolomiques. Zoologie des invertébrés. Université Paul Sabatier - Toulouse III, 2022. Français. ⟨NNT : 2022TOU30017⟩. ⟨tel-03714705⟩

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