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Relations entre efficacité mitochondriale, balance oxydative et croissance des amphibiens

Abstract : The concept of trade-off is central to our understanding of life history evolution but the underlying mechanisms are still poorly understand. Traditional physiological studies of life history trade-offs focused mainly on the differential allocation of limited resources. During the last decade, numerous studies on functional causes of life history trade-off have shown that oxidative stress was related to different components of animal performances. Here, we propose that the functioning of mitochondria, which is the main site of both energy (adenosine triphosphate, ATP) production and of reactive oxygen species (ROS) generation, could be the link between the resource allocation and oxidative stress processes. From descriptive and experimental approaches, we investigate the relationship between energy flow, oxidative stress and growth in a amphibian anuran model, the common frog Rana temporaria. All studies presented in this thesis aim to consider the overall oxidative balance (pro-oxidants, anti-oxidants and oxidative damages) and the energy flow accounting for mitochondrial efficiency of the energy transduction system (the ATP/O ratio variation) to better understand growth patterns in a ectotherm that influence both survival and reproductive capacities. Chronic exposure to an uncoupler (2,4-dinitrophenol) during tadpole development induced a lower growth rate associated with a decreased mitochondria efficiency of energy transduction and an improved oxidative status (lower ROS production and low oxidative damage despite low antioxidant defenses). In addition, the description of physiological parameters of wild frogs exhibiting dissimilar body size shows a higher energy efficiency transduction in frogs exhibiting high growth rate. Thus, the results on the oxidative balance of frogs show that understanding the relationship between the variables of the oxidative balance involves replacing their physiological role. Altogether, our results suggest that (i) the study of a single oxidative balance setting alone does not allow to conclude on other parameters and on the impact of oxidative stress on the organism; (ii) understanding the mitochondrial efficiency of energy transduction is a factor affecting the flow of energy and could drive the amount of energy available for the animal growth. This thesis demonstrates the need to study the underlying mechanisms of trade-offs in merging the resource allocation and oxidative balance approaches, and open the way for more integrative studies
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Karine Salin. Relations entre efficacité mitochondriale, balance oxydative et croissance des amphibiens. Ecologie, Environnement. Université Claude Bernard - Lyon I, 2011. Français. ⟨NNT : 2011LYO10219⟩. ⟨tel-02891029⟩

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