The Effects Of Temperature Acclimation On The Thermal Tolerance, Swimming Capacity And Growth Performance Of Juvenile Qingbo(Spinibarbus Sinensis)

Oscillations in the earth’s climate produce associated fluctuations in the temperature regimes of many aquatic and terrestrial ecosystems. It is increasingly crucial to investigate the adaption of fish on temperature along with the global climate warming. Thus, we selected qingbo(Spinibarbus sinensis) juveniles as the experimental model, first conducted 2 months of temperature acclimation at 15℃ and 25℃,respectively. Then, the acclimated temperatures were increased or decreased at a rate of2 ℃ per day to 25℃ and 15℃, respectively, and the experimental fish were further acclimated for another 2 months. The fitness related physiological functions such as thermal tolerance capacity, swimming performance, feeding metabolism and growth performance were measured after 1, 2, 4 and 8 weeks of temperature change,respectively. The aims of the present study were to(1) investigate and compare the effect of long term(2 months) temperature acclimation on different physiological functions, and(2) test whether the sensitivities of different physiological functions to acclimation temperature regimes are different by comparing the magnitude and rate of changes in physiological traits after increase(or decrease) of acclimated temperature.The main results of the present study:1. When compared with the low-temperature-acclimated fish, long-term high temperature acclimation(2 months) resulted in higher heat tolerance capacity but lower cold tolerance capacity as suggested by higher CTmax and CTmin. After increase or decrease of acclimation temperature, the CTmax and CTmin of temperature increasing group tend to be stabilized at 2 and 4 weeks of temperature change while those of temperature decreasing group stabilized after 2 w of temperature change.2. When compared with the low-temperature-acclimated fish, long-term high temperature acclimation resulted in higher aerobic metabolic capacity and sustainable swimming performance as suggested by higher MMR and Ucrit, which also elicited higher maintenance energy cost indicated by higher RMR. After increase or decrease of acclimation temperature, all measured variables oftemperature increasing group tend to be stabilized at 2w of temperature change while those of temperature decreasing group stabilized after 4w of temperature change.3. Long-term high temperature acclimated fish showed higher satiated meal size and higher peak postprandial metabolic rate(PMR) compared to those of low temperature acclimated fish. After increase or decrease of acclimation temperature,the feeding level and growth rate of temperature increasing group increased gradually while those of temperature decreasing group showed no significant change across 8w of acclimation period.The main findings of the present study:1. Long-term temperature acclimation showed profound effect on all physiological functions, with high temperature acclimated fish showed narrower thermal tolerance scope, higher aerobic swimming capacity, more active spontaneous movements and higher feeding metabolism.2. Any given variables of experimental fish showed varied sensitivities to either temperature increase or temperature decrease, whereas the difference varied among different physiological functions. For example, the thermal tolerance capacity stabilized more quickly after temperature decrease than temperature increase,whereas it was vice versa in aerobic swimming performance.