Growth rate is associated with reduced oxidative stress and this effect is modulated by the degree of social dominance in males of an African cichlid fish

Abstract

Attaining large body size has several selective benefits, however, increased growth rate has potential costs that can constrain investment in other life history traits, such as reproductive output and territorial defense. Oxidative stress can both constrain and result from growth, potentially mediating life history trade-offs between growth rate and other life history traits. Studies on the oxidative cost of growth have provided mixed evidence, in part because components of oxidative balance, including oxidative damage and antioxidant function, is influenced by investment in other activities in a tissue-specific manner. Here, I examined how among-individual variation in growth rate is linked to oxidative stress, and how this relationship is influenced by markers of social dominance (aggressiveness and relative gonad size) in males of the cichlid fish Astatotilapa burtoni. To this end, 7 markers of oxidative damage and antioxidant function in various tissue types (total of 14 measurements) were assessed in dominant and subordinate males. I found that dominant males grew faster than subordinate males. However, increased growth was linked to reduced oxidative stress. This effect was independent of social status but modulated by the degree of social dominance. Overall, the results are consistent with oxidative stress mediating the link between growth and other life history traits. However, my findings challenge the idea that increased growth rate results in elevated oxidative stress, perhaps due to effective protective mechanisms that can neutralize the oxidative challenge of growth.

Keywords: Antioxidants; Life history trade-offs; Reactive oxygen species; Reproduction; Social hierarchy; Territoriality.