An Interspecific Comparison On Metabolic Models In Five Cyprinid Fish Species

In order to investigate the differences on metabolic models in Cyprinid fish species living in different habitats, and to explore the correlation between metabolic models and metabolic strategies of fish species. We selected five juvenile Cyprinid fish species, i.e. crucian carp(Carassius auratus), common carp(Cyprinus carpio), black carp(Mylopharyngodon piceus), Chinese bream(Parabramis pekinensis) and qingbo(Spinibarbus sinensis) as the experimental models, measured the spontaneous movement, metabolic rate, the aerobic swimming ability and the fast-start escape ability of both fasting and digesting fish at water temperature of 25.0 ± 1.0℃.The results are as follows:1. The postprandial metabolic rate increased immediately after digestion, then slowly returned to the pre-fed level. There was significant difference on resting metabolic rate and the peak of postprandial metabolic response among five juvenile Cyprinid fish species(p < 0.05). The resting metabolic rate of juvenile qinbo was significantly lower than those of all other four fish species(p < 0.05). The peak postprandial metabolic rate of juvenile crucian carp showed the highest value which is significantly higher than all fish species except common carp, whereas the peak postprandial metabolic rate of qingbo showed the lowest value which is lower than all other four fish species(p < 0.05).2. Both species and digestion had significant effects on critical swimming speed and digestion effect varied with species(p < 0.05). In fasting fish, juvenile Chinese bream showed the highest critical swimming speed which followed by qinbo, then common carp and then crucian carp(and black carp). Digestion resulted in significantly 16.3%, 11.1% and 9.7% lower critical swimming speed in juvenile qinbo, Chinese bream and black carp, whereas it showed no effect on critical swimming speed of juvenile crucian carp and common carp, but(p < 0.05). The critical swimming speed of digesting Chinese bream(and common carp) showed the highest critical swimming speed which followed by qinbo(and crucian carp), then black carp.3. The maximum linear acceleration and distance moved within first 120 ms of fast-start escape response varied significantly among fish species, with qingbo showed the highest values which were significantly higher than those of crucian carp and common carp(p < 0.05). Furthermore, digestion resulted in a significant decrease in distance moved within first 120 ms of fast-start response of juvenile crucian carp.4. There was no significant effect in any parameters related spontaneous movement performance between fasting and digesting individuals of all five Cyprinid fish species. However, there were significant differences among different Cyprinid fish species in all measured parameters, with the spontaneous movement level of Chinese bream was higher than those of other fish species(p < 0.05).The main findings are as follow:1. All measured parameters related to spontaneous movement, sustained swimming ability, fast-start escape response ability and postprandial metabolic rate response varied profoundly among different Cyprinid fish species. Qinbo possess the highest locomotor ability but the lowest digestive capacity(indicated by low postprandial metabolic responses), whereas it was vice versa in crucian carp. Such differences among different fish species may be related to their varied habitats and(or) distinct ecological habits.2. Digestion-elicited metabolic increase resulted in profound decrease of critical swimming speed of qinbo, Chinese bream and black carp, while it had no effect on either crucian carp or common carp, i.e. the metabolic model of qingbo and Chinese bream is digesiton-priority model while it is additive metabolic model in crucian carp, common carp and black carp. Furthermore, digestion also resulted in a decease of fast-start swimming ability of crucian carp and qinbo.