硫化物胁迫对凡纳滨对虾血细胞抗氧化酶基因表达的影响

硫化物是水产养殖过程中常见的水体污染物之一,为探讨抗氧化酶在凡纳滨对虾Litopenaeus vannamei血细胞抗硫化物胁迫中的作用,以不同浓度(0 mg·L~(-1)和2.0 mg·L~(-1))的硫化物对凡纳滨对虾进行胁迫,于胁迫后的0 h、6 h、12 h、24 h和48 h取血淋巴,测定血细胞中铜锌超氧化物歧化酶(Cu,Zn-SOD)、锰超氧化物歧化酶(Mn-SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPx)和硫氧还蛋白(TRx)基因表达量的变化。结果显示,Cu,Zn-SOD和TRx的表达量在胁迫的6~24 h显著上升,在48 h时恢复至对照组水平;Mn-SOD和GPx的表达量在胁迫的6~48 h均显著上调;CAT表达水平在胁迫的12 h开始有显著提高。这些结果表明凡纳滨对虾血细胞抗氧化相关基因的表达均被诱导上调,以进行防御;Cu,Zn-SOD、Mn-SOD、GPx和TRx均对硫化物胁迫敏感,在胁迫前期发挥作用,CAT主要在胁迫后期发挥作用。     

盐碱地渗水盐度与钠钾比对凡纳滨对虾生长的影响

为广泛利用滨海盐碱地渗水开展对虾养殖,本文研究了盐碱地渗水不同盐度及钠钾比（Na⁺/ K⁺）对凡纳滨对虾存活、生长、代谢及体内谷草转氨酶（GOT）、谷丙转氨酶（GPT）和Na⁺-K⁺-ATPase等3种酶活性的影响.试验用水盐度分别为5、10和15,各盐度组Na⁺/K⁺分别为20、40、50、60、70和90,试验周期为20 d.结果表明,盐度为15的条件下,凡纳滨对虾的存活、生长、代谢及酶活性表现最佳,在此盐度条件下,Na⁺/K⁺保持在40和50条件下,凡纳滨对虾存活、生长、代谢及酶活力较高.表明盐碱地渗水经适当调配可用于凡纳滨对虾的养殖.     

盐度对凡纳滨对虾体组织蛋白质积累、氨基酸组成和转氨酶活性的影响

本文研究了低、中和高三个盐度水平(分别为3‰、17‰和32‰)对凡纳滨对虾(Litopenaeus vannamei)各组织蛋白质的积累、肌肉谷草转氨酶和谷丙转氨酶活力、肌肉总氨基酸和游离氨基酸组成和含量的影响。结果显示,经过50d不同盐度水平的试验,低盐度组对虾的肝胰腺和血淋巴中可溶性蛋白质含量显著高于中、高盐度组(p<0.05),而肌肉中可溶性蛋白质含量在各处理组间无显著性差异;低、高盐度均导致肌肉中谷丙转氨酶和谷草转氨酶活力升高,但是各处理间的差异不显著;低、高盐度组凡纳滨对虾肌肉总氨基酸和总必需氨基酸含量均显著高于中盐度组(p<0.05),中、低盐度处理组非必需氨基酸含量差异不显著,而低盐度组对虾肌肉中蛋氨酸、丝氨酸、半胱氨酸和脯氨酸含量均显著低于中盐度组(p<0.05),其中脯氨酸为常见的5种主要渗透调节氨基酸之一;低、高盐度组对虾肌肉总游离氨基酸含量显著高于中盐度组(p<0.05),而盐度对机体绝大部分肌肉游离氨基酸含量的影响不显著(p>0.05)。结果显示,当环境盐度偏离凡纳滨对虾最适生长盐度时,其可通过在肝胰腺和血淋巴蛋白质积累及提高自身转氨酶活力,来获得机体在渗透调节供能时所需的氨基酸,而这些氨基酸以脯氨酸为主。     

高盐胁迫对凡纳滨对虾消化及免疫相关酶活力的影响

为探讨高盐对凡纳滨对虾(Litopenaeus vannamei)消化及免疫相关酶活力的影响,实验设置了30、40、50、60共4个盐度梯度。对虾体长(7.84±0.68)cm,养殖密度333尾/m~3,每个梯度设3个平行,实验周期30d。取血淋巴、肌肉、肝胰腺等组织,检测其超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、碱性磷酸酶(AKP)和酸性磷酸酶(ACP)及蛋白酶、脂肪酶、淀粉酶活力。结果表明,盐度显著影响凡纳滨对虾肝胰脏中胃蛋白酶、脂肪酶、淀粉酶的活力(P0.05);随着盐度增加,消化相关酶活力均不断下降,处理间差异显著(P0.05);盐度对凡纳滨对虾不同组织的免疫指标产生影响,表现为随着盐度升高,血淋巴中,AKP活力逐渐升高,ACP、CAT和SOD活力均表现为先升高后降低;肌肉中,AKP、ACP和SOD活力呈现先升高后降低的变化趋势;肝胰脏中,AKP活力呈现先降低后升高再降低的变化趋势,ACP活力高盐处理间差异不显著(P0.05),CAT活力先降低后升高,SOD活力盐度40后逐渐降低。实验结果初步说明,高盐显著影响凡纳滨对虾的消化及免疫相关酶活力,且盐度对不同组织中免疫酶活力影响存在一定的组织特异性,50以上的高盐胁迫对对虾消化和免疫相关酶活力的影响尤为显著。     

亚硝酸盐氮对凡纳滨对虾毒性和抗病相关因子影响

用常规生物毒性实验方法,在不同盐度下进行亚硝酸盐氮对凡纳滨对虾的急性毒性实验;并加亚硝酸盐氮于凡纳滨对虾的养殖环境中,检测与抗病力相关因子的变化。研究亚硝酸盐氮对凡纳滨对虾的毒性和抗病力相关因子的影响。结果表明:盐度对亚硝酸盐氮的毒性有较大影响。盐度为31时,24hLC50、48hLC50、72hLC50和96hLC50分别为314.9mg/L1、75.3mg/L1、00.2mg/L和89.0mg/L;盐度为17时,分别为132.3mg/L、65.6mg/L、51.3mg/L和39.5mg/L。盐度31实验组的亚硝酸盐氮半致死浓度均显著(P<0.05)高于盐度17实验组。在低盐度条件下亚硝酸盐氮的毒性较强。亚硝酸盐氮对凡纳滨对虾抗病力相关因子有显著的影响。亚硝酸盐氮浓度为4.0mg/L和8.0mg/L时,其血细胞数、超氧化物歧化酶(SOD)活力、酚氧化酶(PO)活力、抗菌活力(Ua)、溶菌活力(UL)和血清蛋白含量均显著(P<0.05)低于对照组;不吸污组抗病力相关因子活性均显著(P<0.05)低于吸污组。低浓度的亚硝酸盐氮可降低凡纳滨对虾抗病能力,亚硝酸盐氮浓度越高,其抗病能力越弱。     

饲料中铜水平对凡纳滨对虾免疫相关基因表达和抗菌能力的影响

在饲料中添加0、30和50 mg Cu/kg饲料的蛋氨酸铜,投喂凡纳滨对虾(Litopenaeus vannamei)7、14和21d,检测对虾体组织铜蓄积、免疫相关基因(Toll受体mRNA和溶菌酶mRNA)表达水平和免疫抗菌能力的变化。结果表明:凡纳滨对虾肝胰腺铜含量随着饲料蛋氨酸铜添加量增加及投喂时间延长而显著增加(P0.05);对虾肌肉的铜含量显著低于肝胰腺的铜含量。饲料中铜水平对凡纳滨对虾肌肉、血淋巴及肝胰腺中溶菌酶活性无显著影响(P0.05)。对虾组织SOD活性因饲料中铜水平和投喂时间变化显著,添加30 mgCu/kg组对虾肌肉、血淋巴和肝胰腺中SOD活性在第21天时显著高于其他两组(P0.05)。饲料中铜水平对凡纳滨对虾鳃组织中溶菌酶mRNA表达水平无显著影响,但显著影响鳃组织Toll受体mRNA表达水平(P0.05)。第7天时凡纳滨对虾Toll受体mRNA表达水平随着饲料铜水平升高而显著升高(P0.05);第14和第21天时,Toll受体mRNA表达水平在摄食添加30 mg Cu/kg组最高。人工急性感染溶藻弧菌(Vibrioalginolyticus)实验表明,第7天时,摄食添加50 mg Cu/kg组凡纳滨对虾全致死时间和半致死时间长于未添加铜组和添加30 mgCu/kg组,但在第14天,摄食添加30 mg Cu/kg组的全致死时间和半致死时间最长。研究表明饲料铜添加水平不但影响组织中铜的蓄积,还影响凡纳滨对虾SOD活性和Toll受体mRNA表达水平,从而影响机体的抗弧菌能力。     

凡纳滨对虾各月龄性状的主成分与判别分析

为了研究凡纳滨对虾各性状增长规律和判定最佳生长季节凡纳滨对虾的体格与月龄的关系,选择1～6月龄凡纳滨对虾各1000只,选择全长、体长、第一腹节背高、第三腹节背高、第一腹节背宽、头胸甲长和体重共7个性状,进行主成分与判别分析.结果表明:各月龄凡纳滨对虾性状之间均呈现显著的正相关(P<0.01), 其中以全长与体长的相关性最为明显,1月龄凡纳滨对虾体重与形态性状的相关系数较小.各月龄凡纳滨对虾的主成分有所不同,1～2月龄凡纳滨对虾的第一主成分为长度因子,第二主成分为宽度因子,第三主成分为高度因子;3月龄凡纳滨对虾的第一主成分与1～2月龄凡纳滨对虾一致,但第二主成分为高度因子,第三主成分为体重因子;4～6月龄凡纳滨对虾的第一主成分为体重因子,第二主成分为高度因子,第三主成分为宽度因子.1～3月龄凡纳滨对虾形态性状的增长优先于体重, 4～6月龄凡纳滨对虾体重优先于形态性状的增长.错过最佳生长季节的凡纳滨对虾的与体格大小相符的月龄可通过建立的判别式来判断,总的判别准确率为98.98%,其中2～4月龄凡纳滨对虾的判别准确率为100%.     

饲料添加β-1,3-葡聚糖对凡纳滨对虾生长性能、血清代谢、免疫相关基因表达和抗亚硝酸氮应激能力的影响

实验旨在研究β-1,3-葡聚糖的不同投喂方式对凡纳滨对虾(Litopenaeus vannamei)生长、血清代谢和抗亚硝酸氮应激能力的影响。选用480尾初体重(0.43±0.01) g的凡纳滨对虾, 随机分为4组, 即G0(全程投喂基础饲料)、G1组(全程投喂0.1%β-1,3-葡聚糖饲料)、G2组(0.1% β-1,3-葡聚糖饲料7d+基础饲料7d循环)和G3组(0.1% β-1,3-葡聚糖饲料14d+基础饲料14d循环)。在养殖84d后, 应用亚硝酸钠进行120h亚硝酸氮应激实验。结果显示, 各实验组凡纳滨对虾生长性能和全虾营养成分没有显著性差异。在养殖84d后, G2和G3组凡纳滨对虾肝胰腺脂肪酶活性显著高于G0和G1组(P<0.05), G1、G2和G3组凡纳滨对虾血清胆固醇和甘油三酯含量显著高于G0组(P<0.05), G3组凡纳滨对虾肌肉脂多糖/?-1,3-葡聚糖结合蛋白(LGBP)、酚氧化物酶原(proPO)和超氧化物歧化酶(SOD)mRNA表达显著高于G0和G1组(P<0.05)。亚硝酸氮应激120h, G1、G2和G3组凡纳滨对虾累计死亡率显著低于G0组(P<0.05), G3组凡纳滨对虾累计死亡率显著低于G0、G1和G2组(P<0.05)。在亚硝酸氮应激120h后, 与G0组相比, G1、G2和G3组凡纳滨对虾血清总蛋白含量显著升高(P<0.05), 葡萄糖含量、谷丙转氨酶和谷草转氨酶活性显著降低(P<0.05); G3组凡纳滨对虾肌肉LGBP、proPO和SOD mRNA表达显著高于G0 (P<0.05), G1组凡纳滨对虾肌肉丝氨酸蛋白酶(SP)mRNA表达显著高于G0、G2和G3组(P<0.05)。结果表明, 14d间隔投喂0.1% β-1,3-葡聚糖可能通过促进能量代谢和LGBP、proPO和SOD mRNA表达提高凡纳滨对虾抗亚硝酸氮应激能力。     

饲料中添加壳聚糖季铵盐对凡纳滨对虾生长及非特异免疫的影响

实验研究壳聚糖季铵盐对凡纳滨对虾生长性能及非特异性免疫能力的影响。在饲料中分别添加0、0.05%、0.10%、0.15%和0.20%的壳聚糖季铵盐, 制成5组等氮等能饲料。将900尾[初体质量(3.820.34) g]健康的凡纳滨对虾随机分成5组(45尾4平行), 养殖时间56d。结果表明:饲料中添加壳聚糖季铵盐显著影响凡纳滨对虾的生长, 0.15%实验组凡纳滨对虾的增重率和特定生长率最佳(P0.05)。饲料中添加壳聚糖季铵盐0.1%、0.15%和0.20%能显著提高凡纳滨对虾血清溶菌酶和碱性磷酸酶及酚氧化酶的活性(P0.05)。饲料中添加壳聚糖季铵盐可显著提高凡纳滨对虾抗副溶血弧菌感染的能力(P0.05), 0.15%组的保护效果最好, 其相对免疫保护率为33.24%。壳聚糖季铵盐能显著提高凡纳滨对虾的生长性能和抗病能力, 本实验条件下适宜的添加量为0.15%。     

黑水虻幼虫粉对凡纳滨对虾生长、免疫和脂质代谢的影响

试验旨在研究黑水虻Hermetia illucens幼虫粉替代鱼粉对凡纳滨对虾Litopenaeus vannamei生长性能、非特异性免疫和脂质代谢的影响。以黑水虻幼虫粉分别替代对照组饲料(FM)中10%(BSF10)、20%(BSF20)和30%(BSF30)的鱼粉蛋白质,共配制为四组等氮等脂的实验饲料,饲喂初始体质量为(0.88±0.01) g的凡纳滨对虾7周。结果显示, BSF10组和BSF20组对虾的生长性能与对照组相比无显著变化(P>0.05),但BSF30组对虾的生长性能显著降低(P<0.05)。与对照组相比, BSF20组和BSF30组对虾的全虾粗脂肪含量显著降低,BSF30组对虾血淋巴甘油三酯和总胆固醇水平显著降低(P<0.05),但肝胰腺粗脂肪水平无显著差异(P>0.05)。BSF10、BSF20和BSF30组对虾血淋巴谷丙转氨酶和谷草转氨酶活性显著低于对照组(P<0.05)。BSF10组对虾超氧化物歧化酶活性显著高于对照组, BSF20组对虾总抗氧化能力显著高于其余各组(P<0.05)。BSF30组对虾肝胰腺酸性磷酸酶和碱性磷酸...     

Metabolism and growth of juveniles of Litopenaeus vannamei: effect of salinity and dietary carbohydrate levels

The present study was designed to understand how carbohydrate (CBH) and protein metabolism are related in the penaeid shrimp Litopenaeus vannamei. With this information, we obtained a comprehensive schedule of the protein-carbohydrate metabolism including enzymatic, energetic, and functional aspects. We used salinity to determine its role as a modulator of the protein-carbohydrate metabolism in shrimp. Two experiments were designed. The first experiment evaluated the effect of CBH-salinity combinations in growth and survival, and hemolymph glucose, protein, and ammonia levels, digestive gland glycogen, osmotic pressure, and glutamate dehydrogenase (GDH) of L. vannamei juveniles acclimated during 18 days at a salinity of 15 per thousand and 40 per thousand. The second experiment was done to evaluate the effect of dietary CBH level on pre- and postprandial oxygen consumption, ammonia excretion, and the oxygen-nitrogen ratio (O/N) of juvenile L. vannamei in shrimps acclimated at 40 per thousand salinity. We also evaluated the ability of shrimp to carbohydrate adaptation. We made phosphoenolpyruvate carboxykinase (PECPK) and hexokinase activity measurements after a change in dietary carbohydrate levels at different times during 10 days. The growth rate depended on the combination salinity-dietary CBH-protein level. The maximum growth rate was obtained in shrimps maintained at 15 per thousand salinity and with a diet containing low CBH and high protein. The protein in hemolymph is related to the dietary protein levels; high dietary protein levels produced a high protein concentration in hemolymph. This suggests hemolymph is able to store proteins after a salinity acclimation. Depending on the salinity, the hemolymph proteins could be used as a source of osmotic effectors or as metabolic energy. The O/N values obtained show that shrimp used proteins as a source of energy, mainly when shrimps were fed with low CBH. The role played by postprandial nitrogen excretion (PPNE) in apparent heat increase (AHI) (PPNE/AHI ratio) is lower in shrimps fed diets containing high CBH in comparison with shrimps fed diets containing low CBH levels. These results confirm that the metabolism of L. vannamei juveniles is controlled by dietary protein levels, affecting the processes involved in the mechanical and biochemical transformations of ingested food. A growth depression effect was observed in shrimps fed with low-CBH protein diets and maintained in 40 per thousand salinity. In these shrimps, the hemolymph ammonia concentration (HAC) was significantly higher than that observed in shrimps fed with low CBH and maintained in 15 per thousand salinity. That high HAC level coincided with lower growth rate, which suggests that this level might be toxic for juveniles of L. vannamei. Results obtained for GDH activity showed this enzyme regulated both HAC and hemolymph protein levels, with high values in shrimps fed with low CBH levels and maintained in 40 per thousand salinity, and lower in shrimps fed with high CBH and maintained in 15 per thousand salinity. These differences mean that shrimp with a high-gill GDH activity might waste more energy in oxidation of the excess proteins and amino acids, reducing the energy for growth. It was evident that L. vannamei can convert protein to glycogen by a gluconeogenic pathway, which permitted shrimp to maintain a minimum circulating glucose of 0.34 mg/ml in hemolymph. A high PECPK activity was observed in shrimps fed a diet containing low CBH level indicating that the gluconeogenic pathway is activated, as in vertebrates by low dietary CBH levels. After a change in diet, we observed a change in PEPCK; however, it was lower and seems to depend on the way of adaptation, because it occurred after 6 days when adapting to a high-CBH diet and with little change for the low-CBH diet.     

Effect of the dietary probiotic Clostridium butyricum on growth,intestine antioxidant capacity and resistance to high temperature stress in kuruma shrimp Marsupenaeus japonicus

A 56-day feeding trial followed by an acute high temperature stress test were performed to evaluate the effect of dietary probiotic Clostridium butyricum (CB) on growth performance and intestine antioxidant capacity of kuruma shrimp Marsupenaeus japonicus. Shrimp were randomly allocated in 9 tanks (30 shrimp per tank) and triplicate tanks were fed with diets containing different levels of C. butyricum (1×10⁹ cfu/g): 0 mg g⁻¹ feed (Control), 100 mg g⁻¹ feed (CB-100), 200 mg g⁻¹ feed (CB-200) as treatment groups. The results indicated that dietary supplementation of C. butyricum increased the growth performance and decreased the feed conversion rate (FCR) of shrimp in the CB-100 group. HE stain showed that C. butyricum increased the intestine epithelium height of M. japonicus. C. butyricum supplemented in diets decreased·O₂^- generation capacity and malondialdehyde (MDA) content, and increased total antioxidant capacity (T-AOC), catalase (CAT) and peroxidase (POD) activity and the expression level of heat shock protein 70 (hsp70) and metallothionein (mt) gene in intestine of shrimp cultured under normal condition for 56 d, while no significant changes in glutathione peroxidase (GPx) activity and ferritin gene expression level. After shrimp exposed to high temperature stress 48 h, the lower level of·O₂^- generation capacity and MDA content, and the higher level survival, activities of T-AOC, CAT, GPx and POD, as well as hsp70, ferritin and mt gene expression level were found in intestine of two C. butyricum groups. These results revealed that C. butyricum could improve the growth performance, increase intestine antioxidant capacity of M. japonicus against high temperature stress, and could be a potential feed additive in shrimp aquaculture.     

An energetic and conceptual model of the physiological role of dietary carbohydrates and salinity on Litopenaeus vannamei juveniles

We are reporting results directed to explain the relation between carbohydrates (CHO), protein metabolism, and the energetic balance of Litopenaeus vannamei juveniles. The interaction of dietary CHO and salinity was measured to try to understand the relation between osmotic control and metabolism, both from a biochemical and energetic point of view. Two experiments were done. In the first experiment, shrimp were fed with 0%, 5%, 33%, and 61% CHO and maintained at 15‰ and 40‰ salinity. Glucose, lactate protein, hemocyanin, ammonia concentration, and osmotic pressure were measured in blood. Digestive gland glycogen (DGG) was measured also. In the second experiment, shrimp were fed with 0% and 38% dietary CHO and maintained at 15‰ and 40‰ salinity. From that shrimp, absorbed energy (Abs) was calculated as: Abs=respiration (R)+ammonia excretion (U) and production (P); assimilated energy (As) was calculated as the product of R×P. Osmotic pressure, hemocyanin, protein, lactate, and blood ammonia increased with the reduction in dietary CHO. In contrast, an increase in blood glucose was observed with an increase in dietary CHO. Digestive gland glycogen (DGG) increased following a saturation curve with a DGG maximum at 33% dietary CHO. Blood metabolites of fasting and feeding shrimp showed the same behavior. Energy balance results showed that shrimp maintained in low salinity and fed without CHO waste more energy in U production than for shrimp maintained in high salinity and fed with high CHO levels. Notwithstanding, the production efficiency was higher in shrimp fed without CHO than that observed in shrimp fed with high CHO independent of salinity. A scheme trying to integrate the relation between CHO and protein metabolism and the way in which both are modulated by salinity is presented. From published and present results, there are two factors that apparently control the use of high dietary CHO levels; α-amylase enzyme-dietary CHO level capacity and glycogen saturation in DG. Production of glucose is limited in shrimp because of saturation of α-amylase when shrimp are fed with diets above 33% CHO. This is the first control point of starch metabolism. The digestive gland is saturated with glycogen in shrimp fed with dietary CHO levels >33%. This is apparently the second control point of CHO metabolism that limits growth rate in such conditions. The high metabolic cost related to high CHO diets could explain why shrimp are well adapted to use protein as a source of energy.     

Combined effect of temperature and salinity on the Thermotolerance and osmotic pressure of juvenile white shrimp litopenaeus vannamei (Boone)

Thermotolerance (CTMax) was determined in L. vannamei in three salinities and five acclimation temperatures 20, 23, 26, 29 and 32 °C. In white shrimp, the CTMax was not significantly affected by salinity (P>0.05). A direct relationship was obtained between CTMax and acclimation temperature. The end point of the CTMax in L. vannamei exposed to different combinations of temperature and salinity was defined as the loss of the righting response (LRR). The acclimation response ratio (ARR) for the juveniles of white shrimp ranged from 0.42 to 0.49; values in agreement with other crustaceans from tropical and sub tropical climates. The osmotic pressure of the hemolymph was measured in control organisms and in organisms exposed to CTMax; significant differences were found in organisms maintained in 10 and 40 psu, but there were no significant differences in hemolymph osmotic pressure in those that were acclimated to 26 psu.     

Effect of probiotic Pediococcus acidilactici on antioxidant defences and oxidative stress of Litopenaeus stylirostris under Vibrio nigripulchritudo challenge

Antioxidant defences and induced oxidative stress tissue damage of the blue shrimp Litopenaeus stylirostris, under challenge with Vibrio nigripulchritudo, were investigated for a 72-h period. For this purpose, L. stylirostris were first infected by immersion with pathogenic V. nigripulchritudo strain SFn1 and then antioxidant defences: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (Gpx), Total antioxidant status (TAS), glutathiones and induced tissue damage (MDA and carbonyl proteins) were determined in the digestive gland at 0, 12, 24, 48 and 72 h post-infection (h.p.i.). In the meantime, TAS was also measured in the blood. Infection level of the shrimps during the challenge was followed by determining V. nigripulchritudo prevalence and load in the haemolymph of the shrimps. Changes in all these parameters during the 72-h.p.i. period were recorded for control shrimps and shrimps previously fed for one month with probiotic Pediococcus acidilactici MA18/5M at 10⁷ CFU g^?1 of feed.Our results showed that immersion with V. nigripulchritudo led to maximal infection level in the haemolymph at 24 h.p.i. preceding the mortality peak recorded at 48 h.p.i. Significant decreases in the antioxidant defences were detected from 24 h.p.i. and beyond that time infection leaded to increases in oxidative stress level and tissue damage. Compared to control group, shrimps fed the probiotic diet showed lower infection (20% instead of 45% at 24 h.p.i. in the control group) and mortality (25% instead of 41.7% in the control group) levels. Moreover, infected shrimp fed the probiotic compared to uninfected control shrimps exhibited very similar antioxidant status and oxidative stress level. Compared to the infected control group, shrimps fed the probiotic sustained higher antioxidant defences and lower oxidative stress level.This study shows that bacterial infection leads to oxidative stress in L. stylirostris and highlighted a beneficial effect of P. acidilactici, suggesting both a competitive exclusion effect leading to a reduction of the infection level and/or an enhancement of the antioxidant status of the shrimps.     

Antioxidant defenses and oxidative stress parameters in tissues of mud crab (Scylla serrata) with reference to changing salinity

The effects of salinity (10, 17 and 35 ppt) on O₂ consumption, CO₂ release and NH₃ excretion by crabs and oxidative stress parameters and antioxidant defenses of its tissues were reported. An increase in salinity caused a decrease in O₂ consumption and CO₂ release and an increase in ammonia excretion by crabs. Lipid peroxidation, protein carbonyl, H₂O₂ levels and total antioxidant capacity of the tissues elevated significantly at 35 ppt salinity except in abdominal muscle where H₂O₂ content was low. Ascorbic acid content of tissues was higher at 17 ppt salinity than at 10 and 35 ppt salinities. With increasing salinity, a gradual decrease in SOD, an increase in catalase, no change in GPx and a decrease followed by an increase in GR activities were recorded for abdominal muscle. While for hepatopancreas, an increase followed by a decrease in SOD and catalase, decrease in GPx and GR activities were noticed with increasing salinity. In the case of gills, a decrease followed by an increase in SOD, a decrease in catalase and GPx and an increase in GR activities were noted when the salinity increased from 10 ppt to 35 ppt. These results suggest that salinity modulation of oxidative stress and antioxidant defenses in Scylla serrata is tissue specific.     

Studies on the immunomodulatory effect of polysaccharide gel extracted from Durio zibethinus in Penaeus monodon shrimp against Vibrio harveyi and WSSV

Oral administration of polysaccharide gel (PG) in shrimp diets revealed immunostimulating potential and disease resistance in Penaeus monodon (black tiger shrimp). PG from the fruit-rind of Durio zibethinus has been characterized to be a pectic polysaccharide with immunomodulating and antibacterial activities. PG inhibited growth of the shrimp bacterial pathogen, Vibrio harveyi 1526, by agar diffusion and broth microdilution tests. Clear inhibition zones on agar plates were observed at the lowest PG concentration of 3.1 mg/ml, where minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for PG were 6.3 and 12.5 mg/ml, respectively. Each group of juvenile shrimps, initial mean body weight 0.29 ± 0.04 g, was housed in a closed-recirculating treated water system and was fed with PG-supplemented diets containing 1, 2 and 3% PG or shrimp basal diet in the control group for 8 and 12 weeks. PG-supplemented diets did not contribute to the overall growth of black tiger shrimp. The immune response was evaluated by analysis of prophenoloxidase activity and total hemocyte count in the shrimp fed PG-supplemented diets for 12 weeks. Prophenoloxidase activity in shrimp fed the 1, 2 and 3% PG-supplemented diet and total hemocyte count in shrimp fed the 1 and 2% PG-supplemented diet were higher (P < 0.05) than those of the control group. The percent survival was higher in groups fed the 1–3% PG-supplemented diets in challenge tests with either white spot syndrome virus (WSSV) or the bacterium V. harveyi 1526 than that of the control group. Relative percent survival (RPS) values in groups fed the 2% PG-supplemented diet showed the highest RPS value for disease resistance of 100% (at Day 6) and 36% (at Day 4) in treated shrimp against viral and bacterial infection, respectively. Mortality of PG-supplemented diets in treated shrimps against WSSV infection was also found to be much lower (P < 0.05) than that of the control group.     

The resistance to ammonia stress of Penaeus monodon Fabricius juvenile fed diets supplemented with astaxanthin

This study was aimed at determining if the increase of body astaxanthin content through dietary supplementation in tiger prawn Penaeus monodon juvenile could enhance its antioxidant defense capability and resistance to ammonia stress. Haemolymph total antioxidant status (TAS) and superoxide dismutase (SOD) were chosen as parameters of shrimp antioxidant capacity. Resistance to chemical stress was evaluated by shrimp survival rate, and haemolymph aspartate aminotransferase (AST) and alanine aminotransferase (ALT). P. monodon 5-day postlarvae were fed diets supplemented with 0 and 71.5 mg kg⁻¹ astaxanthin for 8 weeks. Shrimps were then subjected to 72-h exposure of ammonia at 0.02, 0.2, 2 and 20 mg l⁻¹. The survival rates of the astaxanthin-fed (AX) shrimp were higher than those of the control shrimp under all levels of ammonia except 20 mg l⁻¹, showing that the shrimp's resistance to ammonia stress had been improved by dietary astaxanthin. AX shrimp had higher TAS than control shrimp at ammonia levels higher than 0.02 mg l⁻¹ and lower SOD at all ammonia levels suggested that antioxidation capability had been greatly enhanced. AST in AX shrimp was lower than that in control shrimp under all levels of ammonia stress. ALT in AX shrimp was either lower than or equal to that in control shrimp under various levels of ammonia. Both AST and ALT reflected that shrimp hepatopancreatic function had been improved by dietary astaxanthin. Astaxanthin can become essential for P. monodon when the animal is under ammonia stress.     

Therapeutic Efficacy of a Subunit Vaccine in Controlling Chronic Trypanosoma cruzi Infection and Chagas Disease Is Enhanced by Glutathione Peroxidase Over-Expression

Trypanosoma cruzi-induced oxidative and inflammatory responses are implicated in chagasic cardiomyopathy. In this study, we examined the therapeutic utility of a subunit vaccine against T. cruzi and determined if glutathione peroxidase (GPx1, antioxidant) protects the heart from chagasic pathogenesis. C57BL/6 mice (wild-type (WT) and GPx1 transgenic (GPx^tg) were infected with T. cruzi and at 45 days post-infection (dpi), immunized with TcG2/TcG4 vaccine delivered by a DNA-prime/Protein-boost (D/P) approach. The plasma and tissue-sections were analyzed on 150 dpi for parasite burden, inflammatory and oxidative stress markers, inflammatory infiltrate and fibrosis. WT mice infected with T. cruzi had significantly more blood and tissue parasite burden compared with infected/GPx^tg mice (n = 5-8, p<0.01). Therapeutic vaccination provided >15-fold reduction in blood and tissue parasites in both WT and GPx^tg mice. The increase in plasma levels of myeloperoxidase (MPO, 24.7%) and nitrite (iNOS activity, 45%) was associated with myocardial increase in oxidant levels (3-4-fold) and non-responsive antioxidant status in chagasic/WT mice; and these responses were not controlled after vaccination (n = 5-7). The GPx^tg mice were better equipped than the WT mice in controlling T. cruzi-induced inflammatory and oxidative stress markers. Extensive myocardial and skeletal tissue inflammation noted in chagasic/WT mice, was significantly more compared with chagasic/GPx^tg mice (n = 4-6, p<0.05). Vaccination was equally effective in reducing the chronic inflammatory infiltrate in the heart and skeletal tissue of infected WT and GPx^tg mice (n = 6, p<0.05). Hypertrophy (increased BNP and ANP mRNA) and fibrosis (increased collagen) of the heart were extensively present in chronically-infected WT and GPx^tg mice and notably decreased after therapeutic vaccination. We conclude the therapeutic delivery of D/P vaccine was effective in arresting the chronic parasite persistence and chagasic pathology; and GPx1 over-expression provided additive benefits in reducing the parasite burden, inflammatory/oxidative stress and cardiac remodeling in Chagas disease.