Differences in mitochondrial efficiency explain individual variation in growth performance

The physiological causes of intraspecific differences in fitness components such as growth rate are currently a source of debate. It has been suggested that differences in energy metabolism may drive variation in growth, but it remains unclear whether covariation between growth rates and energy metabolism is (i) a result of certain individuals acquiring and consequently allocating more resources to growth, and/or is (ii) determined by variation in the efficiency with which those resources are transformed into growth. Studies of individually-housed animals under standardized nutritional conditions can help shed light on this debate. Here we quantify individual variation in metabolic efficiency in terms of the amount of ATP generated per molecule of oxygen consumed by liver and muscle mitochondria, and examine its effects both on the rate of protein synthesis within these tissues and on the rate of whole-body growth of individually-fed juvenile brown trout (Salmo trutta) receiving either ...