氨氮对锯缘青蟹的急性毒性和温度对其耗氧率、窒息点的影响

通过急性毒性实验确定了体重（43.5±2.13）g的锯缘青蟹24 h、48 h氨氮半致死浓度和安全浓度分别为179.99 mg/L、129.99 mg/L和20.34 mg/L。体重（20.8±1.55）g的锯缘青蟹24 h、48 h氨氮半致死浓度和安全浓度分别为175.55 mg/L、131.35 mg/L和20.06 mg/L。锯缘青蟹耗氧率随温度的而增大,在30℃左右达到最大值。体重为（31.6±2.23）g的青蟹,窒息点在15℃时最低为0.17 mg/L,25℃时最高为0.34 mg/L。     

青蟹呼肠孤病毒和青蟹双顺反子病毒-1双重巢式PCR检测方法的建立

青蟹呼肠孤病毒(mud crab reovirus, MCRV)和青蟹双顺反子病毒-1(mud crab dicistrovirus-1, MCDV-1)是从近年发生大规模死亡的养殖拟穴青蟹体内分离的、对青蟹具有致病性的两种病毒。它们常常同时存在, 给青蟹养殖业带来巨大经济损失。在疾病的防治中, 快速高效的病毒检测方法对疾病诊断以及及时采取有效地防治措施具有重要的意义。本研究利用MCRV和MCDV-1基因保守区设计4对引物, 建立了可同时检测这两种病毒的双重巢式PCR(duplex-nested PCR)检测方法。研究发现该方法对两种病毒的检测限都可以达到10个拷贝, 并与鲍肌肉萎缩病毒(AbSV)、虾类传染性表皮与造血组织坏死症病毒(IHHNV)、大菱鲆红体病虹彩病毒(TRBIV)、对虾白斑综合症病毒(WSSV)、鱼类神经坏死病毒(NNV)和贝类急性病毒性坏死症病毒(AVNV)等水生动物常见病毒均无交叉反应, 可以特异性地检测两种病毒。本方法具有高灵敏度、高特异性和简便快捷等特点, 可作为一种快速诊断工具, 检测拟穴青蟹中的MCRV和MCDV-1基因。

     

广东省阳江地区野生拟穴青蟹2种病毒感染情况调查

青蟹双顺反子病毒-1（mudcrabdicistrovirus-1,MCDV-1）和青蟹呼肠孤病毒（mudcrabreovirus,MCRV）是对养殖拟穴青蟹有较强致病性的2种病原,可导致高死亡率。文章采用双重巢式PCR检测法对2012年阳江地区5月-10月捕捞的野生拟穴青蟹（Scyllaparamamosain）病毒感染情况进行调查。结果显示,阳江地区2012年5月～10月的野生青蟹群体一直保持较高的病毒携带率（44．83％-100％）,其中MCDV-1检出率最高的月份为6月、8月和9月,MCRV检出率最高的月份为5月-6月和8月～9月;以单独感染类型为主的月份为5月、7月和10月（〉44．83％）,以双阳性感染类型为主的月份为6月、8月和9月（〉82．76％）。由此可见,2种病毒的流行月份为5月～6月和8月～9月;在流行月份期间2种病毒常常协同感染野生拟穴青蟹。     

拟穴青蟹软壳蟹与硬壳蟹营养品质和风味差异综合比较分析

为明确在最佳收集时间段内不同时间点的软壳蟹和硬壳蟹营养与风味物质的差异,本试验采用顶空固相微萃取(SPME)、气质联用(GS-MS)方法比较了拟穴青蟹硬壳蟹与蜕壳后0~48 h软壳蟹肌肉和肝胰腺2种组织中水分、灰分、氨基酸、矿物质元素、脂肪酸及挥发性物质含量。结果表明,软壳蟹2种组织在蜕壳0 h水分含量最高,硬壳蟹灰分含量显著(P<0.05)高于各时间点软壳蟹。除肝胰腺中胱氨酸和丙氨酸外,2种组织硬壳蟹其他氨基酸含量均高于软壳蟹,其中亮氨酸含量差异显著(P<0.05);在肌肉和肝胰腺组织中,分别有12和14种氨基酸含量均在蜕壳后6 h最高。软壳蟹2种组织Ca、Mg和Fe含量高于硬壳蟹,但差异不显著;蜕壳0 h 软壳蟹肝胰腺组织中Ca含量显著高于其他时间点(P<0.05)。蜕壳后24 h软壳蟹肌肉和0 h肝胰腺组织中∑PUFA均高于其他时间点。2种组织中挥发性物质包括烷烃类、醛类、酮类、醇类、芳香烃类、酯类、酚类和醚类化合物,总体相对含量有差异,但差异不显著。综上比较,拟穴青蟹软壳蟹蜕壳后0~6 h肝胰腺和肌肉比其他时间点更具营养、风味更加,是制取软壳蟹最佳时间。本研究结果为软壳蟹生产、营养和风味评价、市场价值评估提供了一定的参考。     

Morphological deformities in mud crab Scylla serrata juveniles exposed to antibiotics during the larval stage

The effects of antibiotics on the external deformities, growth and survival of mud crab Scylla serrata larvae and juveniles were determined. Zoeae were exposed to oxytetracycline (OTC) (0, 3.0, 6.0, 9.0, 12 mg L^?1) and furazolidone (FZD) (0, 0.5, 1.0, 1.5, 2.0 mg L^?1) in the first and second experiments, respectively, until the late megalopa. The crab instars were grown in nursery tanks for 1 month. Larvae survived until megalopa only at 3.0 and 6.0 mg L^?1 OTC or 0.5 and 1.0 mg L^?1 FZD. These four concentrations were run simultaneously in another experiment. Morphological deformities in zoea 5 were bent dorsal, rostral and furcal spines. There was no significant difference (P > 0.05) on the deformities of zoea 5 in 3.0 and 6.0 mg L^?1 OTC and 0.5 and 1.0 mg L^?1 FZD. Significantly (P < 0.05) higher survival and faster growth were attained in 3.0 mg L^?1 OTC and 0.5 mg L^?1 FZD. Deformities observed in juveniles were fused frontal and lateral spines, asymmetrical and depressed tip of abdominal flap and gap between sternites. High percentage occurrence of deformities was observed in the 6.0 mg L^?1 OTC and 1.0 mg L^?1 FZD in the first and third experiments, respectively. There was no significant difference (P > 0.05) observed in the survival of juveniles in OTC and FZD treatments. However, growth was significantly (P < 0.05) faster in lower concentrations of the two antibiotics. The study shows the effects of OTC and FZD in the morphology of mud crab. Therefore, there is a need to eliminate the use of antibiotics and find alternatives.     

盐度突降对拟穴青蟹仔蟹生长发育和Na＋／K＋-ATP酶活性的影响

研究了盐度（6、13、20、27和33）对拟穴青蟹仔蟹（Scylla paramamosain）生长发育和Na＋/K＋-ATP酶活性的影响。结果表明，盐度对拟穴青蟹仔蟹特定生长率（甲宽和体重）、C3蜕壳间期、甲宽增量（C1至C2和C2至C3）及Na＋/K＋-ATP酶活性有显著影响（P〈0．05），但对仔蟹存活率、C2蜕壳间期及C3至C4甲宽增量无显著影响（P〉0．05）.盐度13处理组特定生长率最高、蜕壳间期最短，盐度69．1：理组特定生长率最低，但与盐度20、27和33处理组无显著差异（P〉0．05），而盐度33处理组蜕壳间期的延长降低了其生长速度；除C1蜕壳为C2的甲宽增量以盐度20处理组最大外，C2、C3蜕壳后的甲宽增量均为盐度13处理组最大；不同盐度条件下，仔蟹Na＋／K＋-ATP酶活性在实验开始后12h、48h、168h和264h时分别表现为盐度6〉13〉20〉27〉33、6〉13〉27〉20〉33、6〉13〉20〉27〉33和6〉13〉33〉20〉27的趋势，低盐环境下酶活性的升高可能有助于拟穴青蟹仔蟹对低渗环境的调节。试验结果表明，拟穴青蟹C1～C3的适宜盐度下限为13以上，C3后对低盐环境的适应能力明显增强，可在盐度6以上的低盐度环境中正常生长。     

Optimum time for weaning South African <Emphasis Type="Italic">Scylla serrata</Emphasis> (Forskål) larvae from rotifers to <Emphasis Type="Italic">Artemia</Emphasis>

To determine the optimum time at which to wean Scylla serrata larvae from rotifers onto Artemia two experiments were conducted, approximately 1 month apart, using larvae from two different female crabs. In the first experiment, the larvae in three treatment groups, with nine replicates each, were fed rotifers for the first 8 days after hatching. Artemia were introduced on days after hatch (DAH) 0 – during the first zoeal instar (treatment R + A); on DAH 4 – during the second zoeal instar (treatment R4A); on DAH 8 – during the third zoeal instar (treatment R8A). In a control (ROT) larvae were fed with rotifers exclusively for 18 days until the completion of metamorphosis to megalopa. In the second experiment, the same four feeding schedules as in experiment 1 were used with an additional group of larvae (treatment AC) that were fed only on Artemia throughout the rearing period. Similar results were recorded in the two experiments. Larvae in treatments R + A and R4A performed significantly better than those in treatments R8A, ROT and AC. This was particularly evident when examining the proportion of zoeae which successfully completed metamorphosis to megalopa. Poor performance of larvae in treatments AC and ROT implied that rotifers are needed as a first food, but that rotifers alone do not fill the nutritional requirements of S. serrata larvae. Poor performance of larvae in treatment R8A suggested that the diet should be supplemented with Artemia before the end of the zoea 3 stage.     

Influence of highly unsaturated fatty acids in live food on larviculture of mud crab Scylla paramamosain (Estampador 1949)

Two experiments were carried out to investigate the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels in rotifers (Brachionus plicatilis) and Artemia on the survival, development and metamorphosis of mud crab Scylla paramamosain larvae. Five different lipid emulsions, varying in the level of total n‐3 and n‐6 highly unsaturated fatty acids (HUFA), DHA, EPA and ARA were used to manipulate the fatty acid profile of the live food. Fatty acid profiles of the live food and crab larvae at zoea one, three and five stages were analysed to study the HUFA uptake by the larvae. The fatty acid content of the live food affected the fatty acid profiles of the crab larvae. In both experiments, the survival rate in the zoeal stages was not statistically different among treatments. However, larval development rate and metamorphosis success were affected by the dietary treatments. In this respect, the DHA/EPA ratio in the live food seems to be a key factor. Enrichment emulsions with a very high (50%) total HUFA content but a low DHA/EPA ratio (0.6), or zero total HUFA content caused developmental retardation and/or metamorphosis failure. An emulsion with a moderate total HUFA (30%) and a high DHA/EPA ratio (4) was the best in terms of larval development during the zoeal stages and resulted in improved metamorphosis. Dietary ARA seemed to improve first metamorphosis, but its exact role needs further clarification. For the larval rearing of S. paramamosain, an enrichment medium containing about 30% total n‐3 HUFA with a minimum DHA/EPA ratio of 1 is recommended. Further investigation is needed on the total HUFA and optimum DHA/EPA ratio requirements for each crab larval stage.     

Apparent digestibility of some nutrient sources by juvenile mud crab, Scylla serrata (Forskal 1775)

As part of preliminary work aimed at the development of a formulated diet for the mud crab, Scylla serrata, an experiment was conducted with juvenile mud crabs (95.65±2.17 g) to determine apparent digestibility coefficients (ADC) for cellulose, fish meal, shrimp meal, blood meal, soybean meal, wheat flour and cod liver oil. Apparent digestibility coefficients for dry matter (ADC_dm), energy (ADC_energy) and protein (ADC_protein) were in the ranges 70.0–95.7%, 77.4–97.1% and 57.7–97.9% respectively. Soybean meal had the highest ADC_dm and wheat flour had the lowest value (P<0.05), while the ADC_dm for fish meal, blood meal and shrimp meal were not different (P≥0.05). Similarly, soybean meal had the same ADC_energy as that of fish meal, but higher than those of cod liver oil, blood meal and shrimp meal (P<0.05). Moreover, the ADC_protein for blood meal or shrimp meal were not significantly different from fish meal (P≥0.05); nevertheless, they were lower than that of soybean meal and higher than that of wheat flour (P<0.05). Of significant interest was the ADC_dm (78.0%) and ADC_energy (77.4%) for cellulose, which indicates that plant‐based nutrient sources may well be a useful component of formulated diets for mud crabs.     

锯缘青蟹脑内5-HT和NPY的免疫细胞化学定位

为探讨5-羟色胺和神经肽Y在锯缘青蟹脑内的存在与否和分布状况，应用免疫细胞化学技术，在光学显微镜下观察5-羟色胺和神经肽Y阳性细胞和神经髓质的形态和分布。结果表明：在锯缘青蟹脑中共12个胞体群和11个神经髓质中，前脑和中脑中有4个细胞群和6个神经髓质检出5-HT免疫阳性反应；中脑和后脑中有7个细胞群和3个神经髓质具有NPY免疫阳性反应。5-羟色胺和神经肽Y在锯缘青蟹脑内的特异性分布，为其参与神经牛理活动提供了形态学证据。