Salin 2015 Abstract MiP2015
|Individual variation in whole-organism performance is related to mitochondrial properties at high temperatures.|
As global temperatures rise, there is a growing need to understand the proximate causes that determine the boundary of an organism’s thermal niche. Individuals can vary in how they respond to temperature increases, but the mechanisms responsible for this inter-individual variation are unclear.
Here we tested the hypothesis that individual performance at high temperatures depends on mitochondrial respiratory properties. We assessed the food intake in an ad libitum diet, rate of growth in mass and length, and mitochondrial function in liver and white muscle of juvenile brown trout Salmo trutta gradually acclimated to the high testing temperature (19°C).
Food intake and growth rate were highly variable amongst fish: food intake varied by 10 among individuals, some fish did not grow, some lost body weight whilst others grew and increased body mass. Around 50% of the individual variation in food intake was explained by liver and muscle mitochondrial function. Individuals with the highest LEAK respiration in liver and muscle exhibited the lowest food intake. Moreover, food intake was worst in individuals with a lower muscle phosphorylating respiration, and in turn a lower respiratory control ratio (RCR). After accounting for food intake, no aspect of mitochondrial function could explain individual variation in growth. Our results demonstrate that individuals with higher LEAK respiration and lower coupling in mitochondria (as estimated by the RCR) had the poorest performance, suggesting that their capacity for ATP production at 19°C could not support an adequate foraging. Our findings suggest that differences in the ability of mitochondria to generate ATP could shape the boundary of an individual’s thermal niche.