低温暴露和恢复对棘胸蛙雌性亚成体生存力及能量物质消耗的影响

棘胸蛙(Paa spinosa)亚成体在人工驯养过程中容易出现越冬困难,非正常的冬眠可能会影响次年的繁育。以雌性棘胸蛙亚成体(1—2龄)为对象,研究该蛙在人工低温暴露(4℃保持90 d)条件下的生存力、机体能量物质消耗、肥满度、脏器系数的变化特征,以及这些参数在温度恢复至正常(由4℃缓慢升至22℃后保持7 d)后的变化情况。结果表明,该蛙在低温暴露过程中存活率逐渐降低,恢复期无死亡。肥满度(K)和体重/体长(Kwl)在低温暴露期间有逐渐升高的趋势,但两者在经历恢复期(22℃,7 d)后均恢复至初始水平(P>0.05)。胃系数和脾系数在低温暴露期呈明显的上升趋势(P<0.05),且两者在第90天均显著大于初始水平(P<0.05)。恢复期肝系数显著减小(P<0.05)。在低温暴露期各阶段肝脏和肌肉脂肪含量与初始无统计差异(P>0.05);肝脏水分在低温暴露期间呈明显下降趋势(P<0.05),而肌肉水分则与之相反;肝脏非脂肪干物质含量呈显著上升趋势(P<0.05),而肌肉非脂肪干物质则呈相反趋势。肝糖原含量随暴露时间的延长呈现显著上升趋势(P<0.05),低温暴露第60天和第90天肝糖原含量与初始相比分别增加59.4%和60.1%,而恢复期肝糖原含量则降至初始水平(P>0.05)。根据结果可以看出,在低温暴露过程中肝脏和肌肉脂肪含量变化不显著,同时肥满度、肝系数、肝脏非脂肪干物质和肝糖原含量均有不同程度的升高,而肌肉非脂肪干物质则显著减少(P<0.05),说明该蛙雌性亚成体在低温期主要消耗的能量物质不是脂肪而是肌肉非脂肪干物质,或者肌肉非脂肪干物质在组织间发生了大量转运。

Effects of cold exposure and recovery on viability and energy consumption in the sub-adult female giant spiny frogs (Paa spinosa)

The giant spiny frog(Paa spinosa),a typical amphibian,can exhibit abnormal hibernation caused by disturbances in energy and substrate metabolism,and can suffer decreases in egg quality during the following breeding season,especially for individuals spawning for the first time.Hibernation which is formed in the long evolutionary process of poikilothermal animals can be considered as a survival strategy and self-protective method to avoid starvation,cold,diseases and other adverse environmental factors for amphibians.Overwintering difficulty of amphibians is a widespread consequence of global climate change and habitat modification that result from human activities,and the following breeding can be influenced by abnormal hibernation with regard to the sub-adult female giant spiny frogs,which is common under the circumstance of artificial domestication.The aim of our study was to investigate the changes in viability and substrate utilization under the condition of artificial cold exposure(4 ℃,90 d) and during recovery(22 ℃,7 d) in the sub-adult female spiny frogs(1—2 year old) which were chosen as the objectives in the study.The results indicated that the survival rate of sub-adult female giant spiny frogs appeared to be a decreasing trend during the period of cold exposure and the mortality rate turned to be zero in the stage of recovery;the relative fatness(K) and the ratio of body weight to body length(Kwl),which presented to be ascendant during cold exposure,both returned to the initial levels(P > 0.05) in the recovery stage;ascendant trend was found in both stomach and spleen coefficient during cold exposure(P<0.05),particularly the both appeared to be higher in the 90th day in relation to the initial levels(P<0.05),and the liver coefficient decreased dramatically in the recovery stage(P<0.05).During cold exposure period,no statistical differences were observed in the lipid content in liver and muscle compared with the initial content levels(P >0.05);the moisture content in liver(P<0.05) and the non-lipid dry matter content in muscle both decreased during cold exposure;the moisture content in muscle and the non-lipid dry matter content in liver(P<0.05) increased during cold exposure;hepatic glycogen content increased by the 60th and 90th day of cold exposure compared to the initial level(P <0.05),with the growth rates of 59.4% and 60.1% respectively,and returned to the initial level during recovery(P > 0.05).We might draw a conclusion that the sub-adult female spiny frogs made use of the non-lipid dry matters in muscle rather than lipid,or the non-lipid dry matters in muscle were transported in the tissues in order to adapt to cold exposure,which was concluded from the facts that the body condition indexes(K and Kwl),liver coefficient,non-lipid dry matter content in liver and hepatic glycogen content emerged to be ascendant to some extent,however,non-lipid dry matter content in muscle proved to be remarkably decreasing(P <0.05)and no significant changes were detected in the lipid content in liver and muscle during cold exposure.