Understanding how organisms can cope with environmental conditions is a mainstream topic, even more so with the current period of rapid climate changes. Anthropogenic global warming induces an increase of averaged temperature, but also an increase of extreme climatic events, such as heatwaves. These quick and large temperature variations could have dramatic consequences on organisms inhabiting freshwater ecosystems, by increasing the metabolic cost of living. Indeed, ectotherms, such as fish, exhibit a metabolic rate closely related to the water temperature. Warmer temperatures induce higher energy expenditure, and therefore higher costs of maintenance and lower energy available for in vivoperformance. Intuitively, whole animal performance is linked to cellular efficiency to provide energy, but this relationship is still unclear. Through various studies conducted in our lab combining in vivo experiments (swimming performance, respirometry) and in vitro protocols (high-resolution oxygraphy, mitochondrial efficiency), we dealt with acute vs. chronic, stable, or variable environmental acclimation, to highlight how cellular bioenergetics can show plastic coping responses to let fish perform under environmental constrains.
