Compensatory growth and oxidative stress in a damselfly

Abstract

Physiological costs of compensatory growth are poorly understood, yet may be the key components in explaining why growth rates are typically submaximal. Here we tested the hypothesized direct costs of compensatory growth in terms of oxidative stress. We assessed oxidative stress in a study where we generated compensatory growth in body mass by exposing larvae of the damselfly Lestes viridis to a transient starvation period followed by ad libitum food. Compensatory growth in the larval stage was associated with higher oxidative stress (as measured by induction of superoxide dismutase and catalase) in the adult stage. Our results challenge two traditional views of life-history theory. First, they indicate that age and mass at metamorphosis not necessarily completely translate larval stress into adult fitness and that the observed physiological cost may explain hidden carry-over effects. Second, they support the notion that costs of compensatory growth may be associated with free-radical-mediated trade-offs and not necessarily with resource-mediated trade-offs.

Figure 1

(a) Growth rate (black bar, non-starved; white bar, starved) and (b) age and mass of the damselfly L. viridis as a function of starvation status through time (filled circles, non-starved; open circles, starved). The categories starved and non-starved refer to the treatment applied during the starvation period. Values are means±1 s.e.m. Successive points in (b) give bivariate means for age and mass at the start and the end of the starvation period, and at the end of the post-starvation period and at emergence, respectively. Slopes of the age versus mass line during the post-starvation period: non-starved larvae, 0.93 mg d⁻¹ and starved larvae: 1.46 mg d⁻¹.

Figure 2

Oxidative stress response variables (a) SOD and (b) CAT of the damselfly L. viridis as a function of starvation status through time. CAT was log transformed. The categories starved and non-starved refer to the treatment applied during the starvation period. Values are means±1 s.e.m. Numbers above the symbols in (a) denote sample sizes. Solid line with filled circles, non-starved; dotted lines with open circles, starved.