Abstract

Despite concerns about environmental contamination, the consideration of long-term effects induced by chronic exposure to contaminants in populations over several generations remains limited in ecotoxicological studies and risk assessment. Similarly, in natural environments, evidence that multigenerational exposure influences the sensitivity of organisms is still scarce, and the mechanisms have yet to be elucidated. Given the lack of knowledge about the importance of the multigenerational effects of chemical contamination in aquatic populations, this work aimed to investigate the role of plasticity in the variability of sensitivity and life-history traits in natural populations of Gammarus fossarum during chronic exposure to cadmium. For that, two types of approach were used: (1) a comparative approach between fifteen populations naturally exposed or not due to the local geochemical context (exposure assessed by bioaccumulation biotests by in situ gammarids’ caging), based on measurements of tolerance and life history traits after sampled in the field, or after keeping a few populations in uncontaminated water for several months in the lab (common-garden), including offspring from crosses between genitors from different populations, and (2) a controlled multigenerational exposure to cadmium (0.3 µg/L) over 18 months from a gammarid population that was initially unexposed in its native environment. For both approaches, cadmium sensitivity and life history traits (growth rate, size, size at puberty, feeding rates, etc.) were measured at different times of exposure or de-acclimation. This work demonstrated (1) a strong influence of the levels of bioavailable natural contamination on the tolerance levels and life history of the populations, (2) a plasticity of these individual and population characteristics when cadmium exposure is stopped, and (3) non-genetic transmission of tolerance to the offspring depending on the exposure conditions of the progenitors, all of which suggests the possible involvement of epigenetic processes in the modification of sensitivity. In addition, the dynamics of the expression of a metallothionein that responds strongly to cadmium exposure was studied in two organs involved in metal accumulation or detoxification in gammarids (gills, caeca) and in the offspring, with regard to the variations in cadmium tolerance observed between populations and during exposure and common-garden experiments. The results showed a covariation in metallothionein expression levels with Cd tolerance and suggest a role for adaptive transgenerational processes occurring during chronic exposure of populations. These results support the hypothesis of the role of epigenetics in the plasticity of Cd tolerance observed in G. fossarum populations. Thus, this works underlines the important role of plasticity and non-genetic transmission of toxicological tolerance during long-term exposure of natural populations to environmental contamination and thus demonstrates the value of conducting multigenerational studies in environmental species that are not laboratory models in order to improve our understanding of population responses to contamination.

Publications and communications

• Auréline Lalouette, Arnaud Chaumot, Louveline Lepeule, Karen Gaget, Nicolas Delorme, et al.. Cadmium tolerance is associated with metallothionein gene expression plasticity in Gammarus fossarum field populations. 2024. ⟨hal–04792699⟩
• Auréline Lalouette, Davide Degli Esposti, Laura Garnero, Maxime Allibert, Lysiane Dherret, et al.. Acclimation and transgenerational plasticity support increased cadmium tolerance in Gammarus populations exposed to natural metal contamination in headwater streams. Science of the Total Environment, 2023, 903, pp.166216. ⟨10.1016/j.scitotenv.2023.166216⟩. ⟨hal–04371960⟩
• Davide Degli Esposti, Auréline Lalouette, Karen Gaget, Louveline Lepeule, Zineb Chaabi, et al.. Identification and organ–specific patterns of expression of two metallothioneins in the sentinel species Gammarus fossarum. Comparative Biochemistry and Physiology. Part B, Biochemistry and Molecular Biology, 2024, 269, pp.110907. ⟨10.1016/j.cbpb.2023.110907⟩. ⟨hal–04704318⟩

Key words

Metallothionein, Multigeneration, Gammarus fossarum, Life History Trait, Tolerance, Natural populations, Plasticity, Parental effects

Cite the thesis

Auréline Lalouette. Place de la plasticité dans la variabilité de la sensibilité toxicologique et des traits d'histoire de vie des populations de Gammarus fossarum exposées à la contamination chronique des cours d'eau par le cadmium. Ecologie, Environnement. Université Claude Bernard - Lyon I, 2023. Français. ⟨NNT : 2023LYO10212⟩. ⟨tel-04813444⟩

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