Comparative Study On The Swimming Performance And Capacities Of Mitochondrial Metabolism In Spinibarbus Sinensis And Myxocyprinus Asiaticus

The swimming performance of fish shows great phenotypic differences at the interspecific level and has obvious correlation with its energy metabolism mechanism.In order to explore the interspecific differences and relationships between swimming performance and mitochondrial energy metabolism of two Cyprinidae fishes with different ecological habits.In this study,the Spinibarbus sinensis in the rapids habitat and the Myxocyprinus asiaticus in the slow-moving habitat were used to compare swimming performance and mitochondrial energy metabolism in two swimming acceleration modes（Critical swimming speed group:ΔV=10 cm/s,Δt=20 min;Burst swimming speed group:ΔV=20 cm/s,Δt=2 min）and individual metabolic rates were measured in two experimental fish,heart.And the respiratory rate of mitochondria and the activity of cytochrome c oxidase（CCO）in heart,red muscle and brain tissues of two experimental fishes were measured under three substrates（complexⅠ-substrate:glutamate+malate;complexⅡ-substrate:succinate;mixed substrate:glutamate+malate+succinate）.The main results obtained in this study are as follows:1.There was no significant difference in resting metabolic rate between S.sinensis and M.asiaticus;the oxygen consumption rate of the two kinds of fish increased with the increase of swimming speed,and there was a significant positive correlation between them(S.sinensis:U_burstgroup（y=7.32x+190.47）,U_critgroup（y=8.13x+85.26）;M.asiaticus:U_burstgroup（y=6.93x+179.19）,U_critgroup（y=5.07x+183.35）),and at the same swimming speed,the oxygen consumption rate of S.sinensis was significantly higher than that of M.asiaticus.2.The critical swimming speed(U_crit),burst swimming speed(U_burst)and maximum metabolic rate（MMR）of S.sinensis were higher than those of M.asiaticus.3.The mitochondrial respiration rate and CCO activity of heart and red muscle tissue of S.sinensis and M.asiaticus were at a high level,while the mitochondrial metabolism level of brain tissue was relatively low.4.Under the condition of mixed substrates,the respiratory control rate（RCR）of mitochondria in heart,red muscle and brain tissue of two Cyprinidae fishes was greater than 4,indicating that the respiratory coupling efficiency of the three tissues of the two experimental fishes were better under the mixed substrates..Under the condition of complex type I substrate（glutamate+malate）,the RCR values of mitochondria in other tissues of S.sinensis and M.asiaticus were higher than those under the condition of complex type II substrate（succinate）,except for the mitochondria of heart tissue of M.asiaticus.5.The state 4 respiration rate of mitochondria in three tissues of S.sinensis and M.asiaticus under the condition of glutamate+malate as substrate were lower than that under the condition of succinate.The three tissue mitochondria of the two fish showed high proton leakage rate when using complex II-type substrates.6.Under the condition of glutamate+malate as substrate,the state 3 respiration rate of brain and heart mitochondria of S.sinensis was significantly higher than that under the condition of succinate（P<0.05）,while the red muscle showed the opposite trend.The state 3respiration rate of brain,heart and red muscle mitochondria of M.asiaticus with succinate as substrate was significantly higher than that under the condition of glutamate+malate（P<0.05）.7.Except that the state 3 respiration rate of red muscle mitochondria of M.asiaticus under succinate substrate condition was significantly higher than that under mixed substrate condition（P<0.05）,the metabolic intensity of mitochondria in other tissues of S.sinensis and M.asiaticus under mixed substrate condition were at a high level.In general,the tissues of the two experimental fish showed higher oxidation ability to mixed substrates.8.The mitochondrial state 3 respiration rates of heart and red muscle tissues of S.sinensis and M.asiaticus were significantly higher than those of the same tissues of M.asiaticus（P<0.05）.The CCO activity of the two tissues also showed the same interspecific difference.The following conclusions are proposed from the discussion of this study:1.The U_critand U_burstof S.sinensis were significantly higher than those of M.asiaticus,and the duration of exhaustive swimming of the former was also longer,indicating that the swimming ability of S.sinensis was significantly stronger than M.asiaticus.2.The MMR and AS achieved by S.sinensis during swimming were significantly higher than those of M.asiaticus,indicating that the former had stronger aerobic metabolism and could provide more energy to maintain higher speed and longer duration of swimming.3.The maximum respiration rate and coupling efficiency of mitochondria in three tissues of the two experimental fish under mixed substrate conditions were generally higher than those under single substrate conditions.Therefore,the mixed substrate should be used to determine the mitochondrial respiration rate in order to more accurately evaluate and compare the metabolic capacity of mitochondria in different species and different tissues.4.The respiration rate and CCO activity of mitochondria in three tissues of S.sinensis and M.asiaticus were the highest in heart,followed by red muscle,and the lowest in brain tissue,and their metabolism patterns show corresponding tissue specificity.5.The mitochondrial metabolism levels of heart and red muscle tissues of S.sinensis were significantly higher than those of M.asiaticus,while the mitochondrial metabolism ability of brain tissues was not significantly different between the two experimental fish,indicating that the swimming performance of the experimental fish was closely related to the mitochondrial metabolism level of the moving tissues.6.The species specificity of fish metabolic patterns is closely related to the species specificity of their swimming performance,which should be a reflection of their adaptation to different habitats’movement needs and energy allocation strategies.