饲料胆固醇含量对凡纳滨对虾免疫相关基因表达及耐低温低溶解氧胁迫能力的影响

Effects of dietary cholesterol content on immune related genes and resistances to low temperature and low dissolved oxygen stress in white shrimp Litopenaeus vannamei

为探究饲料中胆固醇含量对淡水养殖凡纳滨对虾(Litopenaeus vannamei)免疫相关基因表达及耐低温低溶解氧胁迫能力的影响,在鱼粉含量为10%的基础饲料中分别添加0、1.0、2.0、3.0、4.0 g/kg的胆固醇,制成5组等氮等能饲料(C0、C1、C2、C3和C4,实测胆固醇含量依次为0.78、1.57、2.45、3.43和4.18 mg/g)投喂初始体质量为(0.14±0.03)g的凡纳滨对虾。养殖8周后检测对虾耐低温和低溶解氧胁迫的能力以及急性感染副溶血弧菌(Vibrio parahaemolyticus)后免疫相关基因(Toll受体、IMD和溶菌酶mRNA)相对表达量。结果表明:饲料胆固醇含量显著影响弧菌急性感染后对虾鳃组织Toll受体、IMD和溶菌酶mRNA相对表达量。在弧菌感染进程中,C2组对虾Toll受体和溶菌酶的mRNA表达量表现出最大的变化幅度;而IMD mRNA表达量最大变化幅度出现在C1组,其次为C2组。急性感染弧菌后各组对虾Toll受体和溶菌酶mRNA相对表达量峰值均出现在感染后24 h;C2、C3和C4组IMD mRNA表达量峰值出现在感染后24 h,而C0和C1组IMD mRNA表达量峰值出现在感染后42 h。急性程序降温胁迫下,C0和C4组对虾100%死亡的温度为15℃;而其他组对虾100%死亡的温度为14℃。急性低溶解氧胁迫下各组对虾的耗氧量和致死溶氧浓度无显著性差异。综上所述:在淡水养殖条件下,饲料中2.45 mg/g的胆固醇含量可以提高凡纳滨对虾的免疫灵敏性,而饲料中胆固醇含量为(1.57~3.43)mg/g时凡纳滨对虾表现出较好的抗低温胁迫能力。

An 8 weeks feeding trial was carried out to investigate the effects of dietary cholesterol content on the immune related genes and resistances to low temperature and low dissolved oxygen stress in white shrimp Litopenaeus vannamei cultured in freshwater.Five isonitrogenous and isoenergetic experimental diets(C0,C1,C2,C3,C4)were prepared to feed shrimps with initial average mass of(0.14±0.03)g and the measured cholesterol content of experimental diets was 0.78,1.57,2.45,3.43 and 4.18 mg/g diet,respectively.The immune related genes(Toll receptor,IMD,and lysozyme)expressions before and after Vibrio parahaemolyticus infection,cumulative mortalities of the shrimp experienced acute low temperature and low dissolved oxygen stresses were detected.The results indicated that dietary cholesterol significantly affected the changes in expression levels of Toll receptor,IMD and lysozyme mRNAs of the shrimp experienced Vibrio challenge.During the 48 h after infection,the shrimp in C2 treatment displayed the largest variations in Toll receptor and lysozyme mRNAs expressions while the shrimp in C1 treatment displayed the largest variation in IMD mRNA expression,followed by shrimp in C2.All the treatments had the peaks of expressions of Toll receptor and lysozyme mRNAs at 24 h postinfection.The shrimp in C2,C3 and C4 treatments displayed the peaks of IMD mRNA expression at 24 h post infection,while 42 h post infection for C0 and C1 treatments.Under the acute process cooling stress,the shrimp in C0 and C4 treatments displayed 100%mortality at 15℃while the shrimp in C1,C2 and C3 treatments displayed 100%mortality at 14℃.There was no significant difference in oxygen consumption and lethal dissolved oxygen concentration between the groups under acute low dissolved oxygen stress.It is therefore suggested that dietary cholesterol of 2.45 mg/g could improve the immune sensitivity of L.vannamei cultured in freshwater,and the shrimp fed diet containing 1.57-3.43 mg/g cholesterol displays better resistance to low temperature stress.