拥挤胁迫对草鱼非特异性免疫功能的影响

The effect of crowding stress on non-specific immune functions of Ctenopharyngodon idellus

摘要:

在实验室条件下利用放养密度和放养时间构建组间差异,模拟养殖过程中草鱼所面临的拥挤胁迫.胁迫第7、14、30、60d后采样测量免疫指标.结果表明, 高密度组(80g?L-1)的血清溶菌酶活性在胁迫后开始升高,并于14d时达峰值, 以后逐渐下降,呈倒"U"型趋势.血清杀菌活性随放养密度的剧增而锐减(P<0.005).白细胞比容在各组间未显示明显差异.而在30d和60d所测的高密度组草鱼的头肾巨噬细胞吞噬百分率和吞噬指数结果显示,高密度组低于对照组(P<0.05).60d后用嗜水气单胞菌进行攻毒实验,高密度组死亡率高达75.0%,中密度组也达到了63.6%,而对照组只有25.0%.同期所测的脾脏脏器系数显示无论高密度组还是中密度组均显著低于对照组(P<0.01),且经解剖和正常鱼对比,发现其脾脏已明显萎缩.各实验组血清皮质醇浓度均在胁迫初期达到最大值,随后降低,至实验后期基本恢复到正常水平.

Abstract:

Under laboratory conditions , the effect of crowding stress on the non2specific immune system and the resistance to fish pathogenic bacterial infection of grass carp ( Ctenopharyngodon idellus) was investigated. We made an inter2group difference by feeding grass carp ( C. idellus) in different densities and time to simulate the crowding stress encountered by aquaculture fish. After stress of 7 , 14 , 30 , 60 days , fish were sampled to examine their immune indexes. The results indicated that the lysozyme activity in serum of high density group (HG) increased after stress and reached a maximum on 14th day , then decreased over time. Plasma bactericidal activity reduced sharply when density increased. Leucocrit value did not show a significant difference among all groups , but phagocytic activity of macrophages from head kidney after crowding stress of 30 and 60 days showed a difference between HG and control group (CG) ( P < 0. 05) . After 60 days stress , fish in each group were challenged with Aeromonas hydrophila by intraperitoneal injection. Mortality rate of HG was 75. 0 % , middle density group (MG) 63. 6 % and control group only 25. 0 %. At the same sampling time , spleen weight indexes of both HG and MG were much lower than CG ( P < 0. 01) . Additionally , cortisol concentration in serum of all experimental groups came to their maximum values at the beginning of the stress , then dropped and recovered to normal level at the end of experiment .