| This study aimed to test the metabolic theory of ecology (MTE), metabolic-level boundaries (MLB) theory, cell metabolism theory and organ size theory by assessing the mass scaling of the resting metabolic rate (RMR), maximum metabolic rate (MMR), masses of metabolically active organs, hematological parameters, metabolic enzyme and metabolites in the crucian carp (Carassius auratus)(4.5-323.9g, n=80), the silver carp (Hypophthalmichthys molitrix)(8.4-349.8g, n=92), and the bighead carp (Aristichthys nobilis)(22.2-282.3g, n=72).The results were as follows:1. The scaling exponents of RMR (br) with increasing M obtained in the crucian carp, silver carp and bighead carp were0.776,0.868, and0.860, and the scaling exponents for MMR (bm) were0.785,0.748, and0.735, respectively. The factorial aerobic scope (FAS) remained almost constant with increasing M in the crucian carp (p=0.831), but negatively correlated with M in the silver carp and bighead carp (p<0.05). The excess post-exercise oxygen consumption (EPOC) in the three species positively correlated with M (p<0.05). The EPOC duration in the crucian carp remained constant (p=0.156) while increased with M in the silver carp and bighead carp (p<0.05).2. The masses of metabolically active organs positively correlated with M in the three species (p<0.05). The scaling exponents for active organs and inactive organs masses with increasing M in the crucian carp were0.956and1.004, respectively. The scaling exponents in the silver carp were0.915and1.008, respectively. The scaling exponents in the bighead carp were0.973and1.002, respectively. 3. All hematological parameters showed no significant relationship with M in the crucian carp. Although the red blood cell counts (RBCC) and the amount of hemoglobin concentration (Hb) per total surface area (Hb/TSAE) also showed no significant relationship with M, the erythrocyte size and Hb increased with M in the silver carp and bighead carp (p<0.05).4. The citrate synthase (CS) activity in red muscle, the lactate dehydrogenase (LDH) activity in hepatopancreas as well as the LDH activity and the lactate concentration in red muscle and white muscle showed significantly positive relationship with M in the crucian carp (p<0.05). The LDH activity in red muscle and white muscle showed significantly positive relationship with M in the silver carp (p<0.05). The LDH activity in white muscle showed significantly positive relationship with M while the lactate concentration in hepatopancreas showed negative relationship with M in the bighead carp (p<0.05).The conclusions suggested in this study were as follows:1. The br in the crucian carp, silver carp and bighead carp were0.776,0.868and0.860, which fell within the range of values reported for other fishes. The br of the crucian carp was close to the0.75suggested by the MTE theory, but were significantly different with0.75in the silver carp and bighead carp. It suggests that0.75value for the metabolic scaling exponent is not universal in fishes.2. Based on the empirical relationship between the metabolic level (L) and scaling exponent (b) according to the MLB theory, the predicted b values are7.5%,23.0%and15.1%deviated from the observed scaling exponents for the RMR in the crucian carp, silver carp and bighead carp, respectively. Our results suggest that the function can roughly predict the scaling exponent of fishes. On the other hand, the bm value in the three species were significantly lower than1.0, which could be due to their lower locomotor performance. Our results support the MLB theory.3. The findings for masses of metabolically active organs with M suggest that the mass-scaling of the RMR in the three species can be partly attributable to variations in the proportion of active/inactive organs, which indicates partial support the organ size theory.4. The erythrocyte size of the silver carp and bighead carp increased with M but with b, higher than0.67. However, the erythrocyte size of the crucian carp did not change with increasing M, even with br was lower than1.0. Therefore, the cell metabolism theory could not describe metabolic scaling in the three species.5. The FAS remained almost constant in the crucian carp, but negatively correlated with M in the silver carp and bighead carp.6. The EPOC and the LDH activity in white muscle of the three species increased with M, which suggests the anaerobic capacity increases during ontogeny. |
