维生素C（Vc）在提高动物抗应激能力和免疫功能方面具有重要作用。冬眠是中华鳖在低温环境下的自然习性，温度骤变也是其在自然环境中要经历的。本研究主要分为三个部分：（1）探讨了外源Vc及冬眠对中华鳖稚鳖Vc合成能力和组织分布的影响；（2）分析了外源Vc及冬眠对中华鳖稚鳖生长，非特异性免疫指标和肝脏SOD活力的影响；（3）研究了急性冷应激对中华鳖幼鳖Vc合成能力和组织Vc含量的影响。主要研究结果如下： 1．在水温25℃下，用含0 mg/kg（基础料）、500 mg/kg和2500 mg/kg Vc的饲料投喂中华鳖稚鳖（29.41 g±5.44 g）4周，而后缓慢降温至7℃使鳖进入冬眠。另外一组始终在25℃饲喂基础料（RT组）。在实验开始（投喂Vc饲料前）、入眠、冬眠4周、冬眠8周和出眠这五个时刻取样。实验证实了中华鳖体内Vc合成的部位是肾脏。Vc0（0 mg/kg），Vc500（500 mg/kg），Vc2500（2500 mg/kg）组稚鳖的Vc合成能力（GLO活力）始终没有显著差异。稚鳖在冬眠4周后GLO活力显著下降，在8周时刻又回升至入眠时的水平，并维持至出眠。说明中华鳖稚鳖在冬眠初期的GLO活力会受到影响，而随着冬眠时间的延长，GLO活力又会恢复。不同水平的外源Vc并没有造成肝脏、肾脏和脑中Vc含量的显著性差异（除了在出眠时刻：Vc500组肝脏Vc含量显著高于Vc2500组）。肝脏、肾脏和脑Vc含量在整个冬眠过程中呈现出不同的变化规律，具有组织特异性。常温组在长期投喂Vc缺乏饲料的情况下，稚鳖的GLO活力和肝脏Vc含量降低。 2. 不同水平Vc饲料对稚鳖的生长、冬眠过程中稚鳖的血细胞比积、血红蛋白含量、脾脏系数、血清溶菌活力均无显著影响。肝脏SOD活力在不同Vc梯度间无显著性差异，其在冬眠过程中变化不显著。稚鳖在入眠时刻的MDA升高，而后又呈现下降趋势，出眠时刻又显著升高。Vc添加组的MDA水平低于对照组。稚鳖在出眠时肝脏系数显著下降，其中Vc500组的肝脏系数显著高于对照组。血细胞比积和血红蛋白含量在出眠时刻显著升高。长期饲喂Vc缺乏的饲料使得稚鳖的特定生长率和肝脏系数显著下降，而肝脏MDA含量显著升高。 3. 在水温29℃下，用基础饲料投喂中华鳖幼鳖（206.31 g±28.33 g）3周，开始急性冷应激实验。应激条件为13℃±0.7℃，6小时。结果如下：急性冷应激不显著影响幼鳖的GLO活力与组织Vc含量。本实验幼鳖与冬眠实验中的稚鳖相比，前者肾脏GLO活力在一定程度上高于后者，但未达到显著性水平（P=0.053）。肝脏和脑Vc含量无显著性差异。另外，我们观测到雌性幼鳖与雄性幼鳖的GLO活力存在较大差别。但由于样本量较少，尚不能断定是否确实存在这种性别差异。

Vitamin C (Vc) has a positive effect on immunity and antioxidant defense capability of animals. Hibernation is a natural habit of the soft-shelled turtle (Pelodiscus sinensis) at low temperature, and acute temperature change is also what the soft-shelled turtle must undergo in the nature. The present study consists of three sections. The first section investigated the effect of dietary Vc and hibernation on biosynthesis of Vc and tissue Vc concentration in juvenile P. sinensis. The second section analyzed the effect of dietary Vc and hibernation on the growth, non-specific immunity and liver SOD activity in juvenile P .sinensis. The third section studied the effect of acute cold stress on biosynthesis of Vc and tissue Vc concentration in juvenile P. sinensis. The main results were as follows: 1. The juvenile soft-shelled turtles (29.41 g±5.44 g, 1 year old) were fed with Vc supplementation at dosages of 0(basal diet)，500 and 2500 mg Vc／kg diets under 25℃. After 4 weeks, the water temperature was slowly reduced to 7℃ and the turtles were induced into hibernation. Another group (RT Group)was fed with basal diet at 25℃ during the whole experiment. Tissues were collected at five stages: beginning of the experiment (before dietary Vc feeding), beginning of hibernation, end of 4 weeks hibernation, end of 8 weeks hibernation and arousal. The results showed that Vc could be synthesized in the soft-shelled turtle’s kidney. There was no obvious relationship between the capability of Vc biosynthesis (GLO activity)and dietary Vc. However, GLO activity varied with the process of hibernation. The GLO activity decreased significantly after 4 weeks hibernation, but it recovered at the end of 8 weeks hibernation, and then remained stable until arousal. It suggested that GLO activity was perhaps influenced in the initial stage of hibernation, and could restore during the later period. Tissue Vc concentration did not show obvious differences among different Vc levels (except at the arousal: liver Vc concentration of Vc500 was higher significantly than that of Vc2500 ). Liver, kidney and brain appeared different Vc dynamics patterns. GLO activity and liver Vc concentration of the RT group decreased after being fed a diet lacking Vc for a long time. 2. SGR、hematocrit、hemoglobin concentration、 spleen coefficient and serum bacteriolytic activity of the juvenile soft-shelled turtles (29.41 g±5.44 g, 1 year old) during hibernation were not clearly affected by dietary Vc. Liver SOD activity did not vary with Vc levels or hibernation stages significantly. MDA concentration increased at the beginning of hibernation,then reduced slowly until it restored at the arousal, which was even higher than the initial level. MDA levels of the Vc treatment was lower than the control group. Liver coefficient decreased obviously at the arousal, when Vc500 was higher than Vc0 group. Hematocrit and hemoglobin concentration elevated remarkably at the arousal. SGR and liver coefficient of the RT Group reduced sigficantly, while MDA level increased remarkably. 3. The juvenile soft-shelled turtles (206.3 g ± 28.3 g, 2 years old) were fed with basal diet under 29℃. After 3 weeks, the acute cold stress was carried out. Stress condition: 13℃±0.7℃，6h. The results showed that GLO activity and tissue Vc concentration did not change obviously. GLO activity of the older juvenile P.sinensis (2 years old ) was higher than that of the younger juvenile P.sinensis (1 year old) in the last experiment, but not significantly (P=0.053). There was no clear difference in tissue Vc concentration between the two ages. In addition, there seemed a sexual difference of GLO activity in older juvenile P.sinensis, which could not confirmed due to un-enough samples.