凡纳滨对虾氨氮急性胁迫应激敏感群体和耐受群体对WSSV敏感性的差异分析

Investigation on the Susceptibility Difference to WSSV between Ammonia Tolerant and Sensitive Litopenaeus vannamei Populations

关键词:  凡纳滨对虾  急性胁迫应激  白斑综合征病毒(WSSV)  耐受群体  敏感群体

Key words:  Litopenaeus vannamei  Acute ammonia stress  White spot syndrome virus (WSSV)  Ammonia-tolerant population  Ammonia-sensitive population

摘要:

凡纳滨对虾(Litopenaeus vannamei)是世界范围内举足轻重的水产养殖品种，在普遍的高密度养殖活动及环境恶化的情况下，逆境胁迫是影响其养成率的主要因素之一，其中，高浓度氨氮胁迫是最普遍的毒理因子。由于对虾抗病性状的遗传力较低，且在受限于测试场地的低选择强度情况下，抗病选育的进展比较缓慢。而对虾的抗逆性具有较高的遗传力，且不具备传染性的特点使得其不受测试场地的限制。因此，本研究以氨氮急性胁迫应激敏感群体(SP)和耐受群体(TP)为实验材料，对其进行白斑综合征病毒(WSSV)敏感性差异分析，首次探索了通过提高对虾对逆境急性胁迫应激的耐受性，从而间接提高其抗病力的可能性。本研究每个群体设3个处理：高浓度氨氮胁迫下 (10 mg/L)WSSV感染组，两群体分别命名为SPAV和TPAV；正常海水条件下(氨氮水平小于 0.01 mg/L)WSSV感染组，分别命名为SPV和TPV；正常海水条件无WSSV感染组(空白对照组)，分别命名为SPC和TPC。结果显示，SP群体(5 h)在WSSV感染后开始死亡的时间显著早于TP群体(16 h)；从感染60 h后，SPAV组的死亡率呈直线上升趋势，到137 h时该组全部死亡，其累积死亡率显著高于SPV(70.42%)和TP群体的2个组TPAV(42.67%)和TPV(18.99%)(P<0.05)。在144 h实验结束时，SPV的累积死亡率为73.67%，显著高于TP群体的2个组TPAV(46.15%)和TPV(18.99%)以及SP群体的对照组SPC(34.79%)；此时，TPAV组的累积死亡率显著高于TPV和TPC组(P<0.05)，而TPV与TPC组间无显著差异。研究表明，逆境毒理因子(氨氮胁迫)会增加对虾对病原的敏感性，而且对氨氮急性胁迫应激耐受力高的群体对病毒的抵抗力也高。本研究为探索提高对虾抗病力而降低养殖过程中的死亡率提供了新的思路和途径。

Abstract:

The deterioration of water quality from the intensive culture system and environmental pollution are common problems in the practical farming of Litopenaeus vannamei. The toxicity from deteriorating water, such as ammonia accumulation, has lethal effect on shrimp and can increase the susceptibility to pathogens, which might cause frequent high mortality in the period of early stage of L. vannamei cultured in the farms. The high heritability of acute ammonia stress in L. vannamei (0.575) indicated its ammonia tolerance could be improved largely by selection. However, the genetic gain of the disease resistance is very slow in shrimp because of the low heritability of disease resistance traits and low selection intensity by the limitation of pathogen infection test. To explore and improve the ability of disease resistance, we performed the WSSV infection test with ammonia-sensitive population (SP) and ammonia-tolerant population (TP) under ammonia stress (10 mg/L), named SPAV and TPAV, the normal ammonia level (<0.01 mg/L), named SPV and TPV, and no ammonia stress without WSSV infection as the control group (<0.01 mg/L), named SPC and TPC. The results showed that SP started to die at 5 h after WSSV infection, which was significantly earlier than that of TP (about 16 h). The mortality rate of SPAV increased rapidly after 60 h and reached 100% at 137 h, which was significantly higher than SPV (70.42%), TPAV (42.67%), and TPV (18.99%). The cumulative mortality rate of SPV was 73.67% at 144 h, which was significantly lower than SPAV, but significantly higher than TPAV (46.15%), TPV (18.99%) and SPC (34.79%). The cumulative mortality rate of TPAV at 144 h was significantly higher than TPV and TPC, but there was no significant difference between TPV and TPC. These results indicated that ammonia stress increases the susceptibility to pathogens, and that the population with high ammonia tolerance have high WSSV disease resistance, which will provide new ideas to improve the disease resistance and reduce mortality.