Abstract：
This experiment was conducted to explore the effects of dietary vitamin C supplementation on non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab (Scylla paramamosain). Mud crabs with an initial weight of 14.67 ± 0.13 g were randomly divided into 6 treatments and fed diets with 0.86 (control), 44.79, 98.45, 133.94, 186.36 and 364.28 mg/kg vitamin C, respectively. The experiment consisted of 6 treatments, each treatment was designed with 4 replicates and each replicate was stocked with 8 crabs. After 42 days of feeding experiment, 2 crabs were randomly selected from each replicate, and a total of 8 crabs in each treatment were carried out 72 h low-temperature challenge experiment. The results showed that crabs fed diets with 186.36 and 364.28 mg/kg vitamin C significantly improved the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in hemolymph and hepatopancreas (P < 0.05). Crabs fed diet with 133.94 mg/kg vitamin C significantly decreased the concentration of nitric oxide (NO) and the activity of nitric oxide synthase (NOS) in hemolymph (P < 0.05). Diet with 133.94 mg/kg vitamin C was improved the activity of polyphenol oxidase (PPO) and the concentration of albumin (ALB) in hemolymph. Crabs fed diet with 133.94 mg/kg vitamin C showed lower concentration of malondialdehyde (MDA) in hemolymph and hepatopancreas than those fed the other diets. Meanwhile, crabs fed diet with 98.45 mg/kg vitamin C showed higher activity of total superoxide dismutase (T-SOD) in hemolymph, and crabs fed diet with 133.94 mg/kg vitamin C showed higher activity of T-SOD in hepatopancreas. Crabs fed diet with 186.36 mg/kg vitamin C significantly decreased the concentration of reduced glutathione (GSH) and the activity of glutathione peroxidase (GSH-PX) in hepatopancreas (P < 0.05). In normal temperature, crabs fed diets with 133.94 mg/kg vitamin C significantly up-regulated the expression levels of gpx (glutathione peroxidase) and trx (thioredoxin) in hepatopancreas compared with the control treatment (P < 0.05). The highest expression levels of relish, il16 (interleukin 16), caspase 2 (caspase 2), p38 mapk (p38 mitogen-activated protein kinases) and bax (bcl-2 associated x protein) in hepatopancreas were found at crabs fed control diet (P < 0.05). Moreover, crabs fed diet with 133.94 mg/kg vitamin C showed higher expression levels of alf-3 (anti-lipopolysaccharide factor 3) and bcl-2 (B-cell lymphoma 2) in hepatopancreas than those fed the other diets (P < 0.05). Under low-temperature stress, crabs fed diet with 133.94 mg/kg vitamin C significantly improved the expression levels of hsp90 (heat shock protein 90), cat (catalase), gpx, prx (thioredoxin peroxidase) and trx in hepatopancreas (P < 0.05). In addition, dietary with 133.94 vitamin C significantly up-regulated the expression levels of alf-3 and bcl-2 (P < 0.05). Based on two slope broken-line regression analysis of activity of PPO against the dietary vitamin C level, the optimal dietary vitamin C requirement was estimated to be 144.81 mg/kg for juvenile mud crab. In conclusion, dietary 133.94-144.81 mg/kg vitamin C significantly improved the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab.
摘要：
本实验旨在探讨膳食补充维生素C对非特异性免疫防御的影响,幼蟹（Scyllaparamamosain）的抗氧化能力和对低温胁迫的抵抗力。将初始体重为14.67±0.13g的泥蟹随机分为6个处理，饲喂0.86（对照）的日粮，44.79、98.45、133.94、186.36和364.28mg/kg维生素C，分别。实验由6种处理组成，每个处理设计有4个重复,每个重复有8只螃蟹.经过42天的饲喂实验，从每个重复中随机选择2只螃蟹，每种处理共8只螃蟹进行了72h低温挑战实验。结果表明，饲喂186.36和364.28mg/kg维生素C的螃蟹可显着提高血淋巴和肝胰腺中碱性磷酸酶（AKP）和酸性磷酸酶（ACP）的活性（P<0.05）。饲喂133.94mg/kg维生素C的螃蟹可显著降低血淋巴中一氧化氮(NO)浓度和一氧化氮合酶(NOS)活性(P<0.05)。133.94mg/kg维生素C的饮食可提高血淋巴中多酚氧化酶（PPO）的活性和白蛋白（ALB）的浓度。饲喂133.94mg/kg维生素C的螃蟹在血淋巴和肝胰腺中的丙二醛（MDA）浓度低于其他日粮。同时,饲喂98.45mg/kg维生素C的螃蟹在血淋巴中显示出更高的总超氧化物歧化酶（T-SOD）活性，饲喂133.94mg/kg维生素C的螃蟹在肝胰腺中显示出更高的T-SOD活性。饲喂186.36mg/kg维生素C的螃蟹可显著降低肝胰腺中还原型谷胱甘肽(GSH)和谷胱甘肽过氧化物酶(GSH-PX)的活性(P<0.05)。在正常温度下,与对照组相比，饲喂133.94mg/kg维生素C的螃蟹显着上调了gpx（谷胱甘肽过氧化物酶）和trx（硫氧还蛋白）在肝胰腺中的表达水平（P<0.05）。津津乐道的最高表达水平，IL16（白细胞介素16），半胱天冬酶2（caspase2），在饲喂对照饮食的螃蟹中，肝胰腺中发现了p38mapk（p38丝裂原活化蛋白激酶）和bax（bcl-2相关x蛋白）（P<0.05）。此外，饲喂133.94mg/kg维生素C的螃蟹肝胰腺中alf-3（抗脂多糖因子3）和bcl-2（B细胞淋巴瘤2）的表达水平高于其他饲粮（P<0.05）。在低温胁迫下,饲喂133.94mg/kg维生素C的螃蟹显著提高了hsp90（热休克蛋白90）的表达水平，猫（过氧化氢酶），GPX,硫氧还蛋白过氧化物酶（prx）和trx在肝胰腺中（P<0.05）。此外,饲粮中添加133.94维生素C可显著上调alf-3和bcl-2的表达水平(P<0.05)。基于二次斜率折线回归分析PPO活性对饲粮维生素C水平的影响,幼蟹的最佳日粮维生素C需求估计为144.81mg/kg。总之,133.94至144.81mg/kg维生素C显著提高了非特异性免疫防御,泥蟹幼蟹的抗氧化能力和抗低温胁迫能力。
