Effect of Temperature Acclimation on Growth and Thermal Tolerance of Juvenile Rhynchocypris lagowskii
In order to investigate effects of different acclimation temperatures on the growth and tempera-ture tolerance of juvenile Rhynchocypris lagowskii,juveniles with initial body weight of(7.96±1.84)g were reared in recirculating water tanks of each 1.0 mX0.6 mX0.8 m with water depth of 0.6 m at stock-ing density of 40 fish per tank at acclimation temperatures of 20,25 and 28 ℃ to probe into the effects of acclimation temperature on growth,liver and foregut digestive enzymes and transaminase activities for 33 d.At the same time,the juveniles were reared in 10 L barrels with a diameter of 25 cm and a water depth of 20 cm and acclimated at 15,20,25 and 28 ℃ to find out the critical temperature,acclimation response rate and temperature tolerance range.After the juveniles were stabilized,warming/cooling was begun at a constant rate of 1.0 ℃/h.When the fish body was initially out of equilibrium,the temperature was the maximum critical temperature(Tcmax)and the minimum critical temperature(Temin)(accuracy of 0.1)],and the fish was released to room temperature for recovery.The results showed that the juveniles grew normally at water temperature of 20 and 25 ℃ during the culture,death was initially observed at water temperature of 28 ℃ with a survival rate of 86.67％.There were significantly increase in final body weight[(9.13±2.22)g and(10.01±2.74)g,respectively],body length[(8.64±0.73)cm and(8.89±0.82)cm]and total length[(10.18±0.79)cm and(10.49±0.95)cm]in the juveniles in 20 ℃ and 25 ℃ groups com-pared with the initial growth parameters(P＜0.05),without significant difference in 28 ℃ group(P＞0.05).The activities of amylase and lipase were higher in the liver and intestines of juveniles in the 25 ℃ treatment group,without significantly higher activity of hepatic amylase in 28 ℃ group,without signifi-cant difference in liver and intestinal protease activities among the three domesticated groups of juvenile fish(P＞0.05).The activity of intestinal amylase was shown to be significantly higher in the 25 ℃ treat-ment group,with significantly higher activity of hepatic lipase than that in the other two groups and sig-nificantly higher activity of intestinal lipase than that in 20 ℃ group(P＜0.05).No significant difference in activity of glutamic-pyruvic transaminase(ALT)was observed between 20 ℃ group and 25 ℃ group(P＞0.05),with the temperature increasing to 25 ℃,significant decrease in activity of ALT(P＜0.05).The ac-tivity of glutamic oxalacetic transaminase(AST)was found to be significantly decreased first and then sig-nificantly increased with the increasing temperature,with significant higher level in 28 ℃ group than that in other two groups(P＜0.05),indicating that the long-term high temperature induced damage to the liver of juvenile fish,which was the cause of death of juvenile fish.Temperature acclimation affected the thermal tolerance of the juvenile fish,and high temperature led to increase the maximum critical tempera-ture and the minimum critical temperature,with the maximum high-temperature acclimation response ratio of(0.86)within 25-28 ℃,and the maximum low-temperature acclimation response ratio value of(0.60)within 20-25 ℃ as well as the thermal tolerance polygon of 403.77 ℃2.In conclusion,like the temperature tolerance of tropical fish,R.lagowskii has strong temperature adaptation ability and can po-tentially compensate for the negative effects of temperature rise or fall by adjusting physiological and bio-chemical processes under near-extreme temperature conditions.
万方数据
