EFFECTS OF ACUTE TEMPERATURE CHANGE ON RESTING OXYGEN|CONSUMPTION RATE AND CRITICAL SWIMMING SPEED IN JUVENILE|SOUTHERN CATFISH (SILURUS MERIDIONALIS CHEN)|ZENG Ling-

The effects of short-term acute temperature change (20℃→10℃ and 20℃→30℃) and long-term temperatureacclimation (10, 20 and 30℃, two weeks) on resting oxygen consumption rate (Resting oxygen consumption rate, VO2)and critical swimming speed (Critical swimming speed, Ucrit) of juvenile southern catfish (Silurus meridionalis Chen)were conducted to examine the different physiological responses of fish underwent acute and chronic temperaturechange. The results of present study showed that the relative critical swimming speeds (Relative critical swimmingspeed, Ur) of 10, 20 and 30 ℃ acclimation group were 1.83, 2.87 and 3.37 BL/s (Body length per second) (P0.05),respectively. The Ur of both acute temperature elevation group and acute temperature decline group was not significantlydifferent from that of corresponding acclimation group (P>0.05). The relationship between Ur and acclimation temperatureshowed as Ur=0.8114T+1.0976(n=37,R2=0.973,P0.05). The VO2 increased profoundly with temperature(P0.05) and those values were 14.91, 28.34 and 44.98 mg O2/kg?h, respectively. Both acute high temperature exposureand acute cold temperature exposure have a significant influence on VO2 of juvenile southern catfish. The VO2 of acutetemperature elevation group firstly increased and then decreased slowly to a relative stable VO2. The peak value (3.1) ofQ10 of VO2 in high temperature exposure group appeared at 0.5h after acute temperature change and was about two foldsthat of control group while the peak value (3.1) of Q10 of VO2 in acute temperature decline group appeared at 8h afteracute temperature change and was about four folds that of control group. It suggested that acute temperature changeexerted a profoundly influence on the metabolic physiological process of juvenile southern catfish. The metabolic responsesto acute temperature decline group differed significantly from that of acute temperature elevation group. Thephysiological stress elicited by acute temperature decline might be much higher than that of acute temperature elevationgroup. When faced the acute change of environmental temperature, juvenile southern catfish can compensate for thephysical negative effect of acute temperature change on swimming performance physiologically. Fish might adjust themetabolism strategy to meet the energy demand of locomotion when necessary and hence increase the fitness of fishduring an acute temperature descendent adversity.