1. While oxidative stress has been hypothesized to function both as a constraint on and a cost of growth, its mediatory role in shaping life history is still highly debated. Empirical studies about the role of oxidative stress in shaping growth responses and the associated costs are scarce and the two hypotheses have never been combined in one study.

2. By directly manipulating oxidative stress we tested its role in determining compensatory growth responses and the associated costs in the damselfly Lestes viridis. We reduced oxidative stress levels using the mitochondrial uncoupler 2,4-dinitrophenol (DNP). To induce a compensatory growth response, half of the larvae in each oxidant treatment was exposed to a transient starvation period, after which food was present ad libitum.

3. As expected, the transient starvation period induced a compensatory growth response, which was associated with increased oxidative damage and costs in terms of performance (reduced escape swimming speed) and physiology (reduced fat content). As expected, DNP exposure reduced oxidative stress and this resulted in the strongest compensatory growth response without any apparent costs and no increase in oxidative damage.

4. By directly downregulating oxidative stress, our results are consistent with the hypothesis that the level of oxidative stress predictably determines the degree of the compensatory growth response and its associated costs. Our data therefore suggest a mediatory role of oxidative stress in shaping life history.

Data were collected from experimental work including life history data from living animals and physiological analyses