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Theses

Étude des effets inter et transgénérationnels de l’exposition parentale au stress chimique chez le crustacé amphipode Gammarus fossarum

Abstract : Most of the current ecotoxicological approaches (i.e. laboratory bioassays, biomarker, in situ tests) assess the effects of contaminants at the individual level on short response time, that do not match the time scale of population dynamics. In addition to toxicity occurring during the chemical exposure of individuals, effects can arise later along the lifetime of organisms and of their progeny. Such delayed effects can lead to significant impact on population demography, resilience and tolerance, as well as on population vulnerability to new environmental disruptions. Studying these effects is a real challenge to improve the understanding of population response to chemical stress in ecosystems. In this context, the main purpose of this thesis was to explore intergenerational and transgenerational effects of parental contaminant exposure and their consequences on the functioning of the populations in the sentinel species Gammarus fossarum (Crustacea). To do so, challenging oneyear lab experiment together with population dynamics modelling were performed. The experimental statement was to only expose the parental generation (F0) and then to monitor the development of successive generations in an uncontaminated environment. Assuming a prevalent involvement of epigenetic mechanisms in the onset of delayed effects, this work explored for the first time the global genomic cytosine methylation level in Gammarus fossarum. The studied epigenetic mark was shown to be sensitive to heat stress, chemical stress (cadmium) and to food starvation in controlled laboratory conditions. A substantial variability in the basal level between several natural populations of Gammarus fossarum was also recorded. In the light of the multi-generational experiments, cascading effects were observed on G. fossarum life history traits until the third offspring generation after the parental exposure to cadmium or 3,4-dichloroaniline. In addition, a significant role of trade-offs between life-history traits and between generations can be suggested in the emergence of delayed effects. These trade-offs translate into the maintenance of demographic population capacity after the parental cadmium exposure and could be consequently constrained by life history strategy of Gammarus fossarum. Hence, these results highlight the interest of expanding the studied response time beyond the first offspring generation and of studying the long-term effects of chemical stress in non-target environmental species. Such approaches can be suggested to improve the understanding of natural population responses to contamination and to upgrade the ecological relevance of the current risk assessment.
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Pauline Cribiu. Étude des effets inter et transgénérationnels de l’exposition parentale au stress chimique chez le crustacé amphipode Gammarus fossarum. Ecotoxicologie. Université de Lyon, 2020. Français. ⟨NNT : 2020LYSET002⟩. ⟨tel-02918500⟩

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