The purpose of this study was to document the reaction rate of the citric acid cycle enzyme citrate synthase (CS) and two principal glycolytic enzymes,lactate dehydrogenase (LDH) and pyruvate kinase (PK),to temperature changes in five closely phylogenetically related cyprinids in the upper Yangtze River,China,and to test whether the enzymatic activity change observed across thermal acclimation is a common characteristic shared in cyprinids.We measured the PK,LDH and CS activity of the juvenile qingbo (Spinibarbus sinensis),Chinese bream (Parabramis pekinensis),grass carp (Ctenopharyngodon idellus),silver carp (Hypophthalmichthys molitrix) and common carp (Cyprinus carpio) after two weeks of acclimation to 15,20,25 and 30℃.The three enzymes displayed diverse responses to the temperature change.CS activity generally decreased with elevated temperatures except for in the Chinese bream.LDH activity was significantly affected by thermal acclimation,and the effect varied significantly among fish species (P<0.001).Temperature acclimation did not alter LDH activity in the qingbo,the Chinese bream or the silver carp.However,the LDH activity of the common carp was positively related to the acclimated temperature,whereas the grass carp’s LDH activity decreased with increasing temperatures.Similarly,PK values from the cyprinid species displayed three distinct modes of change as the temperature increased: the decreasing mode (qingbo and grass carp),the stable mode (common carp and Chinese bream) and the increasing mode (silver carp).The three enzymes in the Chinese bream (stable mode) and the grass carp (decreasing mode) showed an identical change mode,whereas the enzymes of other fish species showed more complex trends in enzymatic activity changes.Thus,the relative magnitude of each enzyme’s activity among the fish species varied profoundly with thermal acclimation.These findings clearly demonstrated that the activity of enzymes from different pathways displayed various responses to temperature acclimation and that the response of the three enzymes is also interconnected.Furthermore,although the experimental fishes are closely phylogenetically related,each enzyme showed a different response under common temperature conditions.