INDIVIDUAL VARIATION OF ENERGY METABOLISM CHARACTERISTICS AND ECOLOGICAL CORRELATION IN JUVENILE QINGBO (SPINIBARBUS SINENSIS)

Metabolic energy fuels all biological processes, and thus, energy metabolism is vitally important for organisms. It has been suggested that individual variation in physiological functions is associated with the energetic metabolism of organisms, which varies considerably due to selection, adaptation and evolution. In order to explore the individual variation of energy metabolism characteristics of fish and its ecological correlation, we measured the resting metabolic rate (RMR), post-exercise peak metabolic rate (PMR), excess post-exercise oxygen consumption (EPOC), post-hypoxia PMR and excess post-hypoxia oxygen consumption (EPHOC) of 44 juveniles of qingbo individually at 25℃. We found that there are large inter-individual variations in the characteristic parameters of energy metabolism of qingbo. The RMR, post-exercise PMR, EPOC, post-hypoxia PMR and EPHOC were 193.62—460.33 mg O₂/(kg·h), 617.9—2165.02 mg O₂/(kg·h), 28.76—267.20 mg O₂/kg, 484.3—1142.97 mg O₂/(kg·h) and 30.27—211.88 mg O₂/kg, respectively. The post-exercise PMR (r=0.348, P=0.010) and post-hypoxia PMR (r=0.449, P=0.002) were positively correlated with RMR. There was a significant negative correlation between EPOC and RMR (r=–0.426, P=0.004), whereas there was no significant relationship between EPHOC and RMR (r=–0.292, P=0.054). Furthermore, there were significant positive correlations between post-exercise PMR and EPOC (r=0.424, P=0.004), post-hypoxia PMR and EPHOC (r=0.391, P=0.009). Moreover, in terms of individual variation, the post-exercise PMR was consistent with post-hypoxia PMR (r=0.673, P<0.001), and EPOC also was consistent with EPHOC (r=0.526, P<0.001). However, post-exercise PMR and EPOC were significantly higher than either post-hypoxia PMR or EPOC (P<0.05). These results showed that the individual of qingbo with higher RMR might facilitate an improvement in the aerobic power output thus to maintain a high swimming ability, whereas the individual with lower RMR possess a relatively high EPHOC, which was helpful to improve the hypoxia tolerance under extreme environmental conditions. These results suggested the inter-individual variation of energy characteristics of qingbo was the result of natural selection during their long-term adaptation to the environment.