Causes of Intra-specific Variation in Metabolic Rate in Zebrafish, Danio rerio

Abstract

Many studies have reported individual differences in resting metabolic rate (RMR), the energetic cost of self-maintenance. Differences among individuals in the energetic cost of self-maintenance may influence life-history decisions and hence, fitness. In this study, we examined potential causes of intra-specific variation in RMR in zebrafish, Danio rerio. First, the repeatability of RMR was determined to check whether a single measure was reflective of future physiological performance. As predicted, RMR was repeatable over a period of three weeks. However, none of stress-coping style, baseline cortisol levels, metabolically-active organ (gill, heart, intestine and liver) mass, aggression or activity levels were correlated with RMR, i.e. none of these factors were significant contributors to individual variation in RMR. These results imply that other factors must be sought to explain the inter-individual variation in RMR observed in zebrafish.