Vaccination Enhances Early Immune Responses in White Shrimp Litopenaeus vannamei after Secondary Exposure to Vibrio alginolyticus

Background

Recent work suggested that the presence of specific memory or some form of adaptive immunity occurs in insects and shrimp. Hypervariable pattern recognition molecules, known as Down syndrome cell adhesion molecules, are able to mount specific recognition, and immune priming in invertebrates. In the present study, we attempted to understand the immune response pattern of white shrimp Litopenaeus vannamei which received primary (PE) and secondary exposure (SE) to Vibrio alginolyticus.

Methodology

Immune parameters and proliferation of haematopoietic tissues (HPTs) of shrimp which had received PE and SE to V. alginolyticus were measured. In the PE trial, the immune parameters and proliferation of HPTs of shrimp that received heat-killed V. alginolyticus (HVa) and formalin-inactivated V. alginolyticus (FVa) were measured. Mortality, immune parameters and proliferation of HPTs of 7-day-HVa-PE shrimp (shrimp that received primary exposure to HVa after 7 days) and 7-day-FVa-PE shrimp (shrimp that received primary exposure to FVa after 7 days) following SE to live V. alginolyticus (LVa) were measured. Phagocytic activity and clearance efficiency were examined for the 7∼35-day-HVa-PE and FVa-PE shrimp.

Results

HVa-receiving shrimp showed an earlier increase in the immune response on day 1, whereas FVa-receiving shrimp showed a late increase in the immune response on day 5. The 7-day-FVa-PE shrimp showed enhancement of immunity when encountering SE to LVa, whereas 7-day-HVa-PE shrimp showed a minor enhancement in immunity. 7-day-FVa-PE shrimp showed higher proliferation and an HPT mitotic index. Both phagocytic activity and clearance maintained higher for both HVa-PE and FVa-PE shrimp after 28 days.

Conclusions

HVa- and FVa-receiving shrimp showed the bacteria agglutinated prior to being phagocytised. FVa functions as a vaccine, whereas HVa functions as an inducer and can be used as an immune adjuvant. A combined mixture of FVa and HVa can serve as a “vaccine component” to modulate the immunity of shrimp.     

舟山海域春季浮游植物生物量及东海原甲藻赤潮频发机制初探

通过2002和2003年春季2个航次对东海舟山群岛及其邻域大面站的浮游植物及期间爆发的大规模东海原甲藻(Prorocentrum donghaiense)赤潮的综合调查,研究了调查海区浮游植物叶绿素a和营养盐的分布特性,分析了赤潮高发区域的生态环境特征,探讨了诱发和控制海域赤潮发生的环境因子.结果表明,2002和2003年春季大面站表层平均叶绿素a浓度分别为1.09±1.63和4.21±5.33 mg·m^-3,调查海区平均为0.70±0.48和2.60±2.99 mg·m^-3,叶绿素a浓度的高值区基本上位于122.5°～123°E间冲淡水形成的锋面区域,此区域营养盐可以得到充分补充,光照条件适宜,也是浮游植物生产力的高值带.2002和2003年东海原甲藻赤潮跟踪期间,表层平均叶绿素a浓度分别高达18.45±11.04和12.47±8.15 mg·m^-3.赤潮发生海域盐度在26～30,赤潮藻生长易受磷的限制.光照条件适宜、营养盐(特别是磷酸盐)能得到较快的补充及锋面辐聚带的形成是赤潮形成的重要条件.     

长江口及邻近海域浮游水螅水母、管水母和栉水母的丰度分布与季节变化

依据2002—2003年长江口及邻近海域(29°00'—32°00'N、122°00—123°30'E)4个季节的海洋调查资料,探讨了该水域小型水母(含水螅水母、管水母和栉水母)总丰度的空间分布特征及季节差异。结果显示,该海域共出现小型水母41种,其中水螅水母28种,管水螅11种,栉水母2种。主要优势种包括管水母大西洋五角水母(Muggiaea atlantica)、双生水母(Diphyes chamissonis)和气囊水母(Physophora hydrostatica)以及水螅水母四叶小舌水母(Liriope tetraphylla)、两手筐水母(Solmundella bitentaculata)和短柄和平水母(Eirene brevistylus),其中大西洋五角水母为冬、春季第一优势种,双生水母则为夏、秋季第一优势种。该水域小型水母总丰度呈明显季节差异,夏季丰度最高((337.33±55.68)个/m~2),春、秋季次之(分别为(142.09±67.71)个/m~2和(132.84±35.17)个/m~2),冬季最低((113.69±32.72)个/m~2)。水温是影响调查区小型水母总丰度季节变化的主要环境因子,小型水母丰度与表层温度显著正相关(P0.01)。盐度是影响小型水母平面分布格局的主要环境因子,春季小型水母丰度与底层盐度正相关(P0.05),夏季与10 m层盐度正相关(P0.01),全年则是与10 m层盐度正相关(P0.01)。此外,调查水域小型水母丰度与其饵料——小型桡足类亦存在显著正相关关系(P0.01)。