不同技术处理的钝齿短浆蟹淋巴液中和麻痹性贝毒毒性的效果

钝齿短浆蟹(Thalamita crenata)淋巴液可以中和麻痹性贝毒(PSP)的毒性, 这个信息为PSP的降毒研究提供重要依据, 但是淋巴液处理方法是否对其毒性中和效果有影响尚不清楚。本研究采用小鼠腹腔注射法, 以淋巴液的PSP毒性中和效果为指标, 探讨抗凝剂、提取方法和冻存条件等淋巴液处理方法对其PSP毒性中和效果的影响, 为蟹淋巴液的制备提供科学依据。分析结果显示, 不同抗凝剂对淋巴液的PSP毒性中和效果有不同程度的影响, 其中EDTA抗凝剂对淋巴液的PSP毒性中和效果最好, 相对于对照组(小鼠致死时间在5 min左右), PSP-EDTA-淋巴液组的小鼠均存活。低浓度EDTA (5 mmol/L)即可起到抗凝作用并保持淋巴液较好的PSP毒性中和效果, EDTA浓度过高反而对PSP毒性中和效果产生抑制作用。在低浓度EDTA条件下, 针头抽取淋巴液的PSP毒性中和效果明显优于组织破碎法。EDTA浓度为5 mmol/L时, 在针头抽取淋巴液组中, 67%的小鼠致死时间超过30 min。相比之下, 组织破碎提取的淋巴液组的小鼠致死时间均分布在8.1~24 min。另外, 蔗糖对淋巴液的冻存起到较好的抗冷冻保护作用。以上结果表明淋巴液处理方法对其麻痹性贝毒毒性中和效果有较大影响。

     

中性植酸酶替代磷酸二氢钙对黑鲷生长和磷利用的影响

以鱼粉、豆粕、菜粕等为蛋白原料设计配方, 磷酸二氢钙的添加量分别为1.5%、1.0%、0.5%和0(对应的饲料组为P1.5、PP1.0、PP0.5和PP0组), 其中PP1.0、PP0.5和PP0组中均添加200 mg/kg的中性植酸酶, 开展为期8周的黑鲷(Acanthopagrus schlegelii)养殖实验, 以探讨中性植酸酶替代磷酸二氢钙对黑鲷生长和磷利用的影响。结果显示, 黑鲷摄食实验饲料8周后, 各组间成活率无显著差异(P>0.05); 摄食饲料PP1.0、PP0.5和对照组(P1.5组)实验鱼的增重率无显著差异(P>0.05), 但均显著高于PP0处理组, 饲料系数则显著低于PP0处理组(P<0.05)。摄食不同饲料的黑鲷全鱼中蛋白质、脂肪、灰分及钙磷含量在不同组间均无显著差异(P>0.05)。添加植酸酶的各组鱼磷的表观消化率均显著高于对照组(P<0.05)。随着磷酸二氢钙添加量的降低, 黑鲷对干物质和蛋白质的表观消化率呈升高的趋势, 当饲料中磷酸二氢钙的添加量降到0时, 黑鲷对干物质和蛋白质的表观消化率显著高于对照组(P<0.05)。以上结果说明, 在本研究配方下, 黑鲷正常生长对饲料有效磷的需求量≥0.51%; 磷酸二氢钙可部分被植酸酶替代, 当黑鲷饲料中含有20%鱼粉、32%豆粕和12%菜粕, 且植酸酶添加量为200 mg/kg时, 与饲料中添加1%的磷酸二氢钙相当; 在不影响黑鲷生长的前提下, 植酸酶部分替代磷酸二氢钙不仅可降低无机磷的添加, 同时可提高饲料中磷的利用率, 降低磷排放。

     

尼罗罗非鱼8个养殖群体线粒体控制区遗传多样性和遗传关系分析

 利用线粒体DNA控制区部分序列对中国8个尼罗罗非鱼 (Oreochromis niloticus) 养殖群体(埃及、吉拉达、美国、鹭业、吉诺玛、宝路、广东、新吉富)的遗传多样性和相互间遗传关系进行了分析。在所分析的237个样本中, 可归结为15种单倍型, 其中单倍型BL1为宝路(BL)、埃及(EGY)、吉拉达(GLD)、吉诺玛(GNM)和鹭业(LY) 5个群体所共享, 但没有一个单倍型为所有群体共享。8个群体内的核苷酸多态位点数(S)在4~83, 平均核苷酸差异数(K)的范围为0.50~37.26, 单倍型多样性(h)为0.190 8~0.802 3, 核苷酸多样性(π)为0.000 8~0.056 9。AMOVA分析与群体间两两比较的遗传分化指数(F_ST)表明, 这些罗非鱼群体存在显著的遗传分化与差异(P<0.01)。利用Kimura two-parameter模型分析的系统发育关系表明: 宝路、广东和新吉富3个群体亲缘关系较近, 它们聚为一大支; 埃及、美国、吉拉达、鹭业、吉诺玛这5个群体聚为另一大支。单倍型网络(NETWORK)结果显示, 8个群体并没有明显的谱系分化。本研究结果旨为尼罗罗非鱼种质资源的聚合利用奠定基础。

     

饲料中添加浒苔对黄斑蓝子鱼生长性能与生理生化指标的影响

试验用黄斑蓝子鱼(Siganus canaliculatus)幼鱼捕自汕头大学南澳临海试验站附近海域, 在海上网箱中暂养半个月后将其转入室内水族缸(容积200 L)中驯养2周, 饵料为自制配合饲料。新鲜浒苔(Enteromorpha prolifera)从汕头市南澳县盐田采得, 用水清洗后晒干, 经小型粉碎机粉碎, 过60目筛, 制成海藻干粉。选取体质量约23 g黄斑蓝子鱼进行试验。在蛋白水平32%、脂肪水平8%的情况下, 配制6种配合饲料, 其中3种饲料分别添加5%、10%和15%的浒苔干粉, 另2种添加10%、15% 浒苔的饲料中还添加0.2%非淀粉多糖酶(NSP酶), 对照组饲料不添加浒苔。养殖试验周期为8周。结果显示: 与对照组相比, 5%浒苔组鱼的生长性能不受影响(P>0.05), 但10%和15％浒苔组鱼的生长性能显著降低(P<0.05); 然而, 在添加0.2% NSP酶的情况下, 10％和15%浒苔组鱼的生长性能与对照组相比无显著差异(P>0.05)。各饲料组鱼的成活率及全鱼的水分、蛋白、脂肪、灰分含量无显著差异(P>0.05)。与对照组鱼相比, 浒苔饲料组鱼肝和肌肉中的过氧化氢酶及谷胱甘肽过氧物酶的活性增高, 丙二醛含量降低。结果表明, 黄斑蓝子鱼配合饲料中浒苔的添加比例可达5%; 在加入一定量NSP酶的情况下, 其添加比例可达10%～15%。饲料中添加适当比例的浒苔可提高鱼体的抗氧化能力。本研究旨在探讨浒苔作为黄斑蓝子鱼配合饲料原料加以利用的可行性, 为浒苔资源开辟一条有效的利用途径, 并为研发高效、低成本蓝子鱼配合饲料提供指导和依据。

     

生物絮团培养过程中养殖水体水质因子及原核与真核微生物的动态变化

在草鱼(Ctenopharyngodon idella)养殖系统中维持碳氮比为20︰1、水温(26.0±2.3)℃、pH7.2~7.8, 24 h不间断供氧以形成生物絮团, 监测培养过程中养殖水体总氮(TN)、总固体悬浮物(TSS)浓度、碱度的动态变化及分析生物絮团的营养组分, 并应用PCR-DGGE技术研究生物絮团的原核及真核微生物组成和动态变化。养殖水体TN变化范围为6.65~11.15 mg/L, 第9天达到峰值(10.11±1.05) mg/L, 第12天后和第0天时的TN水平无显著性差异(P>0.05); TSS浓度在第9天达到最大值(419.67±11.5) mg/L, 第15天后TSS稳定维持在244.67 mg/L; 碱度变化范围为136.68~239.20 mg CaCO₃/L, 第 6天达到峰值后逐渐下降并趋于平稳。生物絮团的粗蛋白含量为30%(干重)。生物絮团原核微生物主要由变形菌门(Proteobacterium)、放线菌门(Actinobacteria)、拟杆菌门(Bacteroidetes)和某些未知不可培养的细菌组成, 蓝细菌(Cyanobacterium)只存在于生物絮团培养前期(第0、5、10天), 产碱菌科细菌(Alcaligenaceae)存在于生物絮团形成的整个过程, 且是第5、10、15天的优势菌。组成生物絮团的真核微生物隶属于原生动物门的斜叶虫属(Loxophyllum)、隐藻纲的隐鞭藻科(Cryptomonadaceae)及Goniomonas属、硅藻纲的双头菱形藻属(Nitzschia)。其中双头菱形藻属为絮团培养初始第0天到15天特有; 斜叶虫属在絮团培养后期分布较多。结论认为, 生物絮团系统在养殖的15 d左右达到稳定运行的状态, 能有效调节养殖系统菌藻分布, 控制养殖水质, 维持整个系统的平衡与良性发展。

     

低氧胁迫对鲢线粒体ATP酶活性及F1-δ基因表达的影响

为研究线粒体ATP酶F₁-δ基因在鲢(Hypophthalmichthys molitrix)中的作用, 采用RACE-PCR技术克隆出该基因全长, 应用半定量RT-PCR法检测该基因在不同组织的表达, 应用实时荧光定量PCR法检测急性低氧胁迫过程中不同溶氧浓度下该基因的组织表达变化。结果显示, 鲢线粒体ATP酶F₁-δ基因全长762 bp, 开放阅读框480 bp, 编码159个氨基酸残基, 5′端非编码区114 bp, 3′端非编码区168 bp。鲢与斑马鱼(Danio rerio)线粒体F₁-δ编码氨基酸序列的相似性最高, 达到89%; 与大西洋鲑(Salmo salar)、罗非鱼(Oreochromis niloticus)、樱花钩吻鲑(Oncorhynchus masou formosanus)、红鳍东方鲀(Takifugu rubripes)的相似性分别为76%、75%、74%、69%; 半定量RT-PCR结果显示, 该基因在鲢心脏、脑、肝、脾和肌肉中均有表达, 且心脏中最高, 肌肉次之; 实时荧光定量PCR结果表明, 水中溶解氧(DO)分别为5.6(对照组)、4.38、3.37、2.11、1.12和0.54 mg/L时, 随着溶解氧浓度的下降该基因在心脏中的表达逐渐下降且均显著低于对照组(P<0.05); 而在脑、肝、脾和肌肉中的表达则先升高后降低。寡霉素抑制法测得低氧胁迫过程中, 鲢心脏等组织中F₁F₀-ATP酶活性均先升高后降低。这表明鲢线粒体ATP酶F₁-δ基因在低氧胁迫中起到一定的作用, 并对ATP酶的合成产生影响。

     

中国明对虾天门冬氨酸转氨酶基因的克隆及氨氮胁迫对其时空表达的影响

利用RACE技术克隆获得中国明对虾(Fenneropenaeus chinensis)天门冬氨酸转氨酶GOT基因(FcGOT)。FcGOT 基因cDNA全长为1 910 bp, 其中, 开放阅读框1 284 bp, 编码427个氨基酸。同源性分析表明, 中国明对虾天门冬氨酸转氨酶GOT氨基酸序列与其他节肢动物高度保守, 与克氏原螯虾(Procambarus clarkii) 和桔粉蚧壳虫 (Planococcus citri) 的同源性分别为78%和73%。系统进化分析表明, FcGOT基因氨基酸序列与克氏原螯虾GOT聚为一支。组织表达分析发现FcGOT基因在肝胰腺、鳃、血细胞、肌肉、心脏、淋巴中均有表达, 其中肝胰腺中表达量最高。氨氮胁迫后, 荧光定量PCR分析结果表明, FcGOT基因在肝胰腺和鳃组织中的表达与对照组相比具有显著差异(P<0.05), 表明FcGOT基因在氨氮代谢方面具有重要的作用, 参与了中国明对虾机体的急性氨氮胁迫应答反应。

     

虾夷马粪海胆溶菌酶基因全长cDNA的克隆与表达分析

本实验采用RT-PCR和cDNA末端快速扩增(RACE)技术克隆得到了虾夷马粪海胆(Strongylocentrotus intermedius)溶菌酶(LYZ)基因的全长cDNA序列。结果表明, 虾夷马粪海胆LYZ基因全长为912 bp, 含有1个480 bp的开放阅读框(ORF), 编码159个氨基酸, 其中第1−20个氨基酸为信号肽, 蛋白计算分子量为17.69 kD, 等电点为7.75。氨基酸比对分析表明, 虾夷马粪海胆LYZ基因与紫球海胆(Strongylocentrotus purpuratus)和刺参(Apostichopus japonicus)的i型LYZ基因相似百分比分别为91.4%和59.3%, 并且含有i型LYZ基因的保守序列DVGSLSCGP (Y)Y(F)QIK, 所以推断本实验克隆的溶菌酶为i型。采用实时定量PCR方法, 以β-actin为内标, 对其在虾夷马粪海胆各组织中的表达进行研究, 发现LYZ基因在围口膜中表达量最高, 其次是齿间肌、管足、肠、体腔液、雄性性腺和雌性性腺。利用脂多糖(LPS)刺激虾夷马粪海胆, 取刺激后不同时间的海胆体腔液, 对该基因的表达差异进行分析。结果表明, 虾夷马粪海胆的LYZ基因在LPS刺激后8 h时表达量最高, 12 h时开始逐步回落, 至36 h时回落至对照组相近水平。本结果可为虾夷马粪海胆免疫学研究及抗病相关分子标记的开发提供参考依据。

     

尼罗罗非鱼(♀)×萨罗罗非鱼(♂)杂交后代F1、F2形态性状的遗传与变异

通过6个可数性状、10个可量性状及24个框架性状, 比较分析了尼罗罗非鱼(Oreochromis niloticus ♀)×萨罗罗非鱼(Sarotherodon melanotheron ♂)杂交后代F₁、F₂形态性状的遗传与变异特征, 方差分析结果表明, 除臀鳍棘数相同外, 杂交F₁、F₂的可数性状数目相近, 位于尼罗罗非鱼与萨罗罗非鱼之间; 杂交F₁体长/全长、框架参数D_3-5/全长、D_6-8/全长、尾柄长/全长、D_5-7/全长、D_8-10/全长等参数显著大于萨罗罗非鱼, 体厚/全长、体高/全长、D_1-6/全长、D_3-4/全长、尾柄高/全长等参数显著大于尼罗罗非鱼; 杂交F₂的16个可量、框架性状与杂交F₁间无显著差异, 而头长/全长、D_5-6/全长、D_7-8/全长、D_9-10/全长等参数显著大于杂交F₁, 躯干长/全长、尾柄长/全长、D_1-2/全长、D_5-7/全长、D_7-9/全长等参数显著小于杂交F₁。聚类分析结果表明, 杂交F₂与杂交F₁先聚为一类, 再依次与尼罗罗非鱼、萨罗罗非鱼聚类。分别建立了不同群体的可数性状、可量与框架性状的判别公式, 判别正确率高低依次为尼罗罗非鱼、萨罗罗非鱼>杂交F₁>杂交F₂; 利用尼罗罗非鱼和萨罗罗非鱼的判别公式对杂交F₁进行判别, 被判入尼罗罗非鱼的比例较高(可数性状92.9%、可量与框架性状57.1%); 利用尼罗罗非鱼、萨罗罗非鱼及杂交F₁的判别公式对杂交F₂判别, 被判入杂交F₁的比例较高(可数性状68.6%、可量与框架性状77.2%)。主成分分布图显示, 杂交F₁、F₂均位于尼罗罗非鱼和萨罗罗非鱼之间, 杂交F₁与尼罗罗非鱼重叠分布较多, 杂交F₂分布重叠区域较F₁分散。以上结果表明, 尼罗罗非鱼♀×萨罗罗非鱼♂杂交F₁形态性状介于亲本之间, 遗传了双亲的形态特征, 且有一定的偏母遗传; 杂交F₂大部分形态特征遗传了杂交F₁, 但也存在一定程度的变异。本研究旨在通过分析尼罗罗非鱼、萨罗罗非鱼2个杂交世代中亲子间形态性状的遗传规律, 为罗非鱼杂交育种研究与生产利用提供基础资料和依据。

     

烟台近海3种贝类中呈味核苷酸和氨基酸的测定及比较分析

对水产品中呈味核苷酸和氨基酸的高效液相色谱检测方法进行了优化, 并对烟台近海长牡蛎(Ostrea gigas)、栉孔扇贝(Chlamys farreri)和中国蛤蜊(Mactra chinensis)3种贝类中呈味核苷酸和氨基酸的含量进行了比较分析, 从而为开发贝类复合调味料提供科学依据。以纯水提取呈味物质, 采用DABS-Cl柱前衍生反相高效液相色谱法测定游离氨基酸, 流动相为17 mmoL/L柠檬酸溶液(pH 6.4, 含4%DMF)和乙腈溶液(含4%DMF), 梯度洗脱, 检测波长436 nm。反相离子对色谱法测定呈味核苷酸, pH 4.5的磷酸二氢钾溶液和乙腈溶液为流动相, 磷酸二氢钾溶液内含5 mmoL/L四甲基氢氧化氨(TMAOH), 梯度洗脱, 检测波长254 nm。方法加标回收率为90.2%~108%, 相对标准偏差(RSD)为0.7%~7.1%。准确度、精密度均满足分析要求。测定结果显示: 长牡蛎中牛磺酸、丙氨酸和谷氨酸含量较高, 栉孔扇贝中甘氨酸、牛磺酸和丙氨酸含量较高, 中国蛤蜊含有较多的甘氨酸、牛磺酸和丙氨酸; 3种贝类中, 丙氨酸、谷氨酸的TAV均大于1, 栉孔扇贝和中国蛤蜊中, 甘氨酸的TAV大于1, 对呈味具有显著贡献。呈味核苷酸中, 长牡蛎中IMP含量最高, 占总呈味核苷酸的80%, 其次是GMP。中国蛤蜊中AMP含量最高, 其次是IMP。而栉孔扇贝中仅检测到IMP。3种贝类中呈味核苷酸含量虽然都较低, TAV未超过1, 但核苷酸之间、核苷酸和氨基酸之间的协同增效作用, 会对贝类的呈味产生重要影响。本研究通过对烟台近海3种贝类中各类鲜味物质和多种辅助呈味物质的含量、比例关系及其相互作用规律进行探讨, 旨在为充分利用贝类营养氨基本作为复合调味料及其功能性开发和评价提供科学依据。

     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.