摄食对鲇鱼幼鱼力竭性运动后过量耗氧的影响

EFFECT OF FEEDING ON EXCESS POST-EXERCISE OXYGEN CONSUMPTION IN JUVENILE CHINESE CATFISH (SILURUS ASOTUS LINNAEUS)

为了检验鲇鱼(Silurus asotus Linnaeus)幼鱼力竭性运动(Exhaustive exercise)后过量耗氧(EPOC)是否受到摄食的影响,以阐明其在两种功能状态下的功率配置模式,在(25.0±1.0)℃条件下,分别测定了对照组(摄食前)、摄食组[摄食12 h,摄食水平为(8.74±0.40)%]、摄食代谢恢复组[摄食60 h,摄食水平为(8.84±0.25)%]鲇幼鱼力竭性运动后EPOC及力竭性运动后恢复过程中呼吸频率(Vf)的变化。研究结果显示:对照组、摄食组、摄食代谢恢复组力竭性运动前耗氧率(MO2)显著差异(P<0.05),而Vf差异不显著;力竭性运动后MO2和Vf均立即达到峰值,随后逐渐恢复到稳定状态;摄食组的耗氧率峰值(MO2peak)[(222.47±10.14)mgO2/(kg.h)]显著大于对照组[(180.53±6.79)mgO2/(kg.h)]和摄食代谢恢复组[(181.65±10.94)mgO2/(kg.h)](P<0.05),但三个组之间Vf无显著变化;摄食组的EPOC总量[(42.49±10.13)mgO2]显著小于对照组[(66.58±6.40)mgO2]和摄食代谢恢复组[(53.46±5.80)mgO2](P<0.05)。以上结果表明:(1)无论是摄食还是运动任一生理功能均不能诱导出鲇鱼幼鱼的最大的MO2;(2)当摄食和运动两种生理功能同时存在时,鲇鱼无氧运动能力减弱,同时力竭性运动后的恢复过程加快,可能与消化导致的内环境碱化减缓了运动后的内环境酸化有关。

Feeding and exercise are normal, essential components of everyday lives of fish. Under natural conditions, animals often need to undertake these two activities simultaneously and it is important to study the interactions between these activities. Thus, to investigate the impact of feeding and subsequent nutrient digestion and absorption on the metabolic and respiratory recovery processes after exhaustive exercise （chasing） in juvenile Chinese catfish （Silurus asotus Linnaeus） （N=30, body mass： 54.51±86.89 g, body length： 19.51±24.59 cm）, the ＂excess post-exercise oxygen consumption＂ （EPOC） of the experimental fish before feeding, 12h after feeding （8.744±0.40）% body mass and 60h after feeding （8.844±0.25）% body mass were studied at （25.0±1.0）℃. The light cycle was 12L ： 12D. Cutlets of freshly killed loach species （Misgurnus anguillicaudatus） without viscera, head and tail were used as the test meal, and oxygen consumption （MO2） was adjusted to a standard body mass of 1 kg using a mass exponent of 0.75. The ventilation frequency （Vf） was also documented before and during the recovery process after exhaustive exercise. No significant differences in either resting MO2 （MO2rest） or Vf （Vfrest） were found after three days of fasting among all experimental groups before the experiment. However, there was significant difference on the MO2 before the exhaustive exercise, i.e. pre-exercise M02, among the three groups. Both the MO： and the Vf increased immediately after exhaustive exercise and slowly returned to pre-exercise values in all three experimental groups. The peak MO2 （MOEpea）values were （180.534±6.79）, （222.474±10.14） and （181.654±10.94） mgOj（kg.h） at Oh （before feeding）, 12h and 60h after feeding and the EPOC values were （66.584±6.40）, （42.49±10.13） and （53.46±5.80） mgO2at Oh （before feeding）, 12h and 60h after feeding, respectively. Both EPOC and MOEpeak of fish in the 12h after feeding group significantly differed from the other two groups （P〈0.05）. Our observation suggested that： （1） neither digestion nor exhaustive exercise led to maximal MO： in juvenile Chinese catfish; （2） exhaustive exercise was curtailed under postprandial exercise, and the post-exercise metabolic recovery process became faster in a postprandial fish when compared to fasting ones. This faster recovery was possibly due to the ＂alkaline tide＂ （metabolic base loading during digestion in vertebrates） elicited by feeding, which significantly prevented the decreases in pH and [HCO3] immediately after exhaustive exercise.