仿刺参纵肌带再生的形态学和组织学

采用人工创伤的方法剪断仿刺参(Apostichopus japonicus)体腔背部的纵肌带, 然后缝合切口处的体壁, 将其在添加抗生素(100 IU/mL的青霉素和100 μg/mL的链霉素)的海水中继续饲养。通过形态学和组织学方法对仿刺参纵肌带再生过程中的结构变化进行了观察。形态学结果显示, 创伤后0 h, 由于纵肌带的收缩, 断端出现0.5~1 cm的间隙; 创伤15 d, 创伤处出现乳白色絮状组织, 暂命名为肌前组织; 创伤30~45 d时, 肌前组织逐渐增厚并将断端肌肉组织连接起来; 创伤60~90 d, 肌前组织已转化成纵肌带, 并且其厚度增至正常纵肌带的1/2; 创伤后110~130 d, 新生纵肌带进一步增粗, 形态上与未创伤处组织没有区别, 只是直径略小一些; 创伤150 d, 再生的纵肌带厚度同正常状态。组织学结果显示, 创伤后15 d, 在损伤处出现结缔组织及单个的肌纤维, 形成一条不规则的细长条带, 即肌前组织; 创伤后30~45 d, 肌前组织中肌细胞数量大量增加, 并与体壁间形成一些“桥状”连接; 创伤后60~90 d, 肌前组织几乎被肌纤维占据, 且“桥状”连接数量增加, 此时肌前组织已转化为肌肉带(纵肌带); 创伤后110~130 d, 新生肌纤维数量大量增加, 和体壁相连的“桥状”连接数量减少, 创伤150 d, 新生的纵肌带基本达到正常的结构, 且“桥状”连接消失。分析认为仿刺参纵肌带具有较强的再生能力, 且新生的肌细胞来源于体壁结缔组织细胞和体腔上皮细胞。

     

中华鲟子二代仔鱼对光照强度的趋性行为

设计4种点光源(100 lx、320 lx、960 lx、1 920 lx)光照模式, 以黑暗和面光源(68 lx)模式为对照, 以30 min为实验周期, 对中华鲟(Acipenser sinensis)子二代仔、幼鱼(5~29日龄)的趋光行为进行观察和统计分析。结果表明, 仔鱼处于平游期(5~8日龄)时, 点光源光照条件下活动鱼苗的趋光率显著高于对照组(黑暗环境和面光源)(P<0.05), 而且点光源光照条件下活动鱼苗的趋光率随着光照强度的增强而增加, 并在1 920 lx与100 lx和320 lx间存在显著性差异(P<0.05)。平游期仔鱼的趋光性最为明显, 在设定的4种点光源光照强度中, 在100 lx的低强度光照下趋光性最强, 在960 lx光照强度下趋光性最弱, 且二者存在显著性差异(P<0.05); 中华鲟子二代进入沉底期以后, 光照的影响作用明显减弱, 仔鱼基本失去趋光性。研究表明, 中华鲟子二代仔鱼具有平游期趋光性最强、趋弱光和沉底之后基本失去趋光性等行为特点, 这种趋光行为与野生中华鲟仔鱼基本一致。研究结果可为阐明中华鲟全人工繁殖后代生态适应性提供参考。

     

基于微卫星标记对长江中上游胭脂鱼增殖放流效果的评估

利用已经发表的11对胭脂鱼多态性微卫星标记, 对长江中上游胭脂鱼(Myxocyprinus asiaticus)增殖放流效果进行评估。结果表明, 5个胭脂鱼养殖场内所有的149尾繁殖亲本和长江中上游采集的65尾胭脂鱼中共观测到140个等位基因, 其观测杂合度和期望杂合度的平均值(范围)分别为0.771(0.519~0.906)和0.759(0.469~0.894), 多态信息含量(范围)为0.726(0.392~0.882)。通过软件Cervus统计得到, 11个微卫星座位累计排除率为99.998 3%, 并且在长江中上游采集的65个样本中, 11个样本与养殖场内繁殖亲本确定存在亲子关系, 据此确定这11尾为增殖放流的胭脂鱼, 并由此推算增殖放流的胭脂鱼对长江中上游野生群体的贡献量为16.92%。研究结果表明, 增殖放流是实现胭脂鱼野生种群资源恢复的有效途径。

     

双齿围沙蚕-牙鲆网箱综合养殖模型碳、氮收支的实验研究

在实验室条件下, 设计相同的牙鲆(Paralichthys olivaceus)鱼苗网箱养殖密度(密度5尾/箱, 鱼苗体质量约21 g), 分别与不同数量的双齿围沙蚕(Perinereis albuhitensis, 0 g, 50 g, 70 g, 90 g)混合养殖, 4个实验组分别记作C、S1、S2和S3, 网箱规格为Ф60 cm×30 cm。各实验组设3个平行组, 实验进行40 d。牙鲆和沙蚕在称重前均饥饿24 h, 同时取5尾牙鲆和20 g沙蚕作为实验初始样品。实验期间, 每天07:30和18:00分2次投喂配合饲料, 根据对照组饵料剩余情况适时调整投喂量, 每个实验单元的投饵量基本一致, 此过程中不处理残饵和粪便。实验单元采用微流水, 流量为250~500 L/d。实验期间, 24 h持续微量充气。至实验结束时, 全部生物饥饿24 h。将其全部取出, 擦干体表水分, 称重后置于70℃干燥箱中烘干至衡重, 研磨、分析。结果表明, 对照组(C)的底质积累碳、氮量最高, 各实验组水体净输出的氮和有机碳量以及呼吸碳量分别无显著差异(P>0.05)。饲料是碳、氮输入的主要来源。在输出各项中, 各个实验组水体净输出氮占输出氮比例无显著差异(P>0.05), 而系统净排放氮以对照组所占比例最高, 但与S1和S2组无显著差异(P>0.05); 对照组底质积累氮所占输出氮比例显著高于S2和S3组(P<0.05)。对照组底质积累碳所占比例显著高于其他各实验组(P<0.05); 对照组和S1组的水体净输出有机碳比例显著高于S3组(P<0.05), 而S3组碳净排放占碳输出的比例显著低于对照组和S1组(P<0.05)。碳、氮产投比均以对照组最低。在本研究条件下, 双齿围沙蚕在综合养殖模型中可利用牙鲆网箱养殖产生的残饵和粪便, 减少底质碳、氮积累, 提高产投比, 综合养殖模型既可以降低碳、氮排放, 又可以增加产品产出。结论认为, 网箱养殖牙鲆搭配双齿围沙蚕的综合养殖模型理论上具有可行性, 双齿围沙蚕可以作为牙鲆网箱养殖产生的残饵和粪便的一道有效处理屏障, 此模型在港湾和围堰鱼类网箱养殖中更有意义。

     

鲤疱疹病毒2型武汉株的分离与鉴定

采用细胞培养、超薄切片电镜观察、巢式PCR检测以及病毒DNA克隆与测序分析等技术, 从湖北武汉一循环水养殖系统中患出血病异育银鲫(Carassius auratusgibelio)体内分离鉴定了一株鲤疱疹病毒2型(Cyprinid herpesvirus 2, CyHV-2)病毒, 命名为鲤疱疹病毒2型武汉株(CyHV-2-WH)。患病鱼组织匀浆液接种锦鲤鳍条细胞系(Koi-Fin)可产生典型的细胞病变效应。用患病鱼组织匀浆液与细胞培养物分别人工感染异育银鲫, 均可重复出与自然发病相同的症状, 死亡率达100%。患病鱼脾与肾脏组织超薄切片电镜观察结果显示, 病毒为具囊膜的球形病毒, 囊膜直径为170~200 nm, 病毒衣壳直径为110~120 nm, 病毒在细胞核内复制、组装。采用CyHV-2的特异引物对病鱼样本和感染细胞培养物样本进行巢式PCR检测, 均能扩增出357 bp的目的条带, 将该扩增产物进行测序与比对分析后发现, 其与GenBank中已报道的CyHV-2毒株的DNA解旋酶基因高度同源(99.44%以上), 与鲤疱疹病毒3型(CyHV-3)也有较高的同源性(81.55%)。系统进化分析结果显示, CyHV-2-WH株与JS2012、H.Fukuda、YC110907等CyHV-2病毒株属同一分支。

     

环境因子对瓦氏马尾藻生长及光合作用的影响

研究不同温度(10、15、20、25、30℃, 光照强度80 μmol穖^?穝^?, 盐度30)、光照强度(20、60、100、200、300 μmol穖^?穝^?, 培养温度20℃, 培养液盐度30)和盐度(盐度10、20、30、40和50, 培养温度20℃, 光照强度80 μmol穖^?穝^?)对瓦氏马尾藻(Sargassum vachellianum)生长、光合色素含量及光合放氧活性的影响。结果表明, 3种环境因子对瓦氏马尾藻生长、光合色素含量及光合放氧活性影响显著(P<0.05)。其中, 瓦氏马尾藻适宜生长条件为: 温度15~20℃, 最适温度为20℃; 光照强度20~60 μmol穖^?穝^?; 盐度20~40, 最适盐度为30。最高特定生长率达5.80%穌^?。温度高于25℃或光照强度大于200 μmol?/SPAN>m^?穝^?或盐度小于10或大于50藻体2两周后基本停止生长并出现发白、变软、腐烂现象。温度10~20℃、光照强度20~60 μmol穖^?穝^?、盐度20~40时较适宜瓦氏马尾藻光合色素的积累。温度20℃、光照强度100 μmol穖g^?穐^?、盐度30时瓦氏马尾藻的光合放氧活性最高, 最高值达258.50 μmol?/SPAN>m^?穝^?。与低光强相比高光强对瓦氏马尾藻光合放氧活性的抑制作用不明显。研究结果为瓦氏马尾藻的栽培和藻场修复提供了理论依据。

     

对虾白斑综合征病毒囊膜蛋白VP110在中国明对虾鳃细胞中结合蛋白的鉴定与特性

为了鉴定对虾白斑病综合征病毒(WSSV)囊膜蛋白VP110在中国明对虾(Fenneropenaeus chinensis)鳃细胞中的结合蛋白, 运用pET-32(a)+载体构建了1段含RGD模体的截短VP110原核重组表达质粒, 转化大肠杆菌诱导表达后获得分子量为41 kD的截短重组VP110蛋白(rVP110)。以rVP110作为诱饵蛋白, 运用pull-down实验结合蛋白质谱分析鉴定rVP110结合蛋白, 结果显示, 中国明对虾鳃细胞中的肌动蛋白和精氨酸激酶(arginine kinase,AK)与rVP110具有结合作用。利用PCR扩增中国明对虾AK编码基因, 将其与表达载体pGEX-4T-1连接后转化大肠杆菌诱导表达获得重组AK蛋白(rAK), 通过pull-down实验进一步证实rAK可与rVP110发生结合。克氏原螯虾(Procambarus clarkia)体内中和实验结果显示, rAK对WSSV感染克氏原螯虾具有一定的中和作用, 能延缓螯虾的死亡进程。另外, 中国明对虾在人工感染WSSV后, 荧光定量PCR检测结果显示, AK基因表达水平显著上调, 18 h时达到峰值, 然后下降至正常水平; 酶底物法检测结果同样显示, 鳃细胞中AK酶活性在感染WSSV后发生显著上调。本研究旨在为深入了解WSSV囊膜蛋白VP110在WSSV感染宿主过程中的作用提供基础依据。

     

绿原酸诱导凡纳滨对虾抗氧化功能及抵御低盐度胁迫的响应

选择健康、均匀, 体质量为(6.74 ± 0.08) g的凡纳滨对虾(Litopenaeus vannamei),  将360尾随机分为4组, 分别投喂含有0 mg/kg、100 mg/kg、200 mg/kg和400 mg/kg绿原酸的饲料28 d, 随后将对虾从盐度为32的天然海水直接转移至盐度为10的海水中暴露72 h, 测定对虾肝胰腺TAS、GPx、CAT活力和GPx、CAT基因表达水平。结果显示, 在天然海水养殖条件下, 绿原酸对凡纳滨对虾肝胰腺TAS、GPx活性无明显影响, 但投喂含有绿原酸的饲料28 d, 对虾肝胰腺GPx、CAT和GPx、CAT基因表达水平显著高于D0组(P<0.05), 以D2组GPx活性和GPx、CAT基因表达水平最高, 分别为164.29 U/mgprot和1.61、2.14倍。低盐度胁迫24 h, D0组对虾抗氧化反应表现在TAS、GPx活性和GPx基因表达水平较28 d显著升高(P<0.05), 分别增加了31.30%、27.96%和170%, 而绿原酸各组对虾肝胰腺TAS、GPx活性和GPx基因表达水平显著低于D0组(P<0.05), 说明绿原酸可有效缓解低盐度胁迫下对虾抗氧化系统酶活性的剧烈波动。低盐度胁迫72 h, 绿原酸各组对虾肝胰腺TAS、GPx、CAT活性及CAT基因表达水平均明显高于D0组。上述结果表明绿原酸能够诱导凡纳滨对虾的抗氧化系统功能, 在凡纳滨对虾抵抗低盐度胁迫中发挥着重要的作用。本研究旨为开发绿色植物提取物在对虾养殖中的应用, 解决盐度胁迫对机体造成的氧化损伤提供理论依据。

     

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。

     

细鳞鲑早期发育过程中的消化系统发生

应用连续切片技术和显微观察法, 对胚胎至幼鱼期的细鳞鲑(Brachymystax lenok)消化系统(口咽腔、胃、幽门盲囊以及肠道等组织)早期发生进行了系统研究。研究表明, 在实验水温为12.0～16.2℃时, 细鳞鲑胚胎期消化系统原基发生与分化的过程为, 在卵受精后125～165 h, 胚胎进入原肠期发育, 随着原肠作用的进行, 脊索开始分化; 卵受精后201 h, 消化系统原基细胞团在脊索下方出现, 为单层的扁平细胞; 卵受精后480 h, 消化系统原基位于脊索和卵黄囊之间, 呈直管状; 卵受精后552 h, 管状消化系统内层细胞大量增殖, 外层由两层细胞构成。细鳞鲑胚后消化系统的发育过程为, 初孵仔鱼即具有富含油球的大卵黄囊, 消化系统呈简单的盲管状, 肛门尚未与外界连通; 2～7 DAH, 仔鱼消化系统分化加快; 7 DAH后, 仔鱼已初步分化出口咽腔、食道、胃、肠以及肝; 10 DAH, 仔鱼消化器官已基本分化完毕, 肛门已向外界连通; 14 DAH, 仔鱼从内源性营养向外源性营养的过渡基本完成, 卵黄囊和油球吸收完毕; 19 DAH, 稚鱼胃固有膜内出现胃腺; 49 DAH, 幼鱼幽门盲囊分化完毕, 肝和胰脏功能完善; 64 DAH, 幼鱼口咽腔和胃的组织结构与成鱼基本相同, 前后肠组织结构相似; 105 DAH, 幼鱼幽门盲囊指状分支已具有28～36个。细鳞鲑仔鱼的最佳人工开口驯化时间应该在10～14 DAH, 可通过不断投喂适口饲料的方式来强化仔鱼的主动摄食行为。本研究旨在为深入了解细鳞鲑仔鱼的消化生理、摄食转变及开口驯化时机提供基础资料。

     

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.     

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).     

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.     

Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven,Hemitripterus americanus

The sea raven, Hemitripterus americanus, is a sit-and-wait, low metabolic rate, marine teleost. The objective of this study was to determine i) whether cortisol implantation (50 mg. kg^-1) for 7 days altered hepatocyte metabolism, and hepatocyte responsiveness to epinephrine, glucagon and insulin, and ii) whether 8 weeks of food-deprivation modified the above response. Cortisol implantation significantly increased hepatocyte total glucose production and oxidation from alanine compared to the sham group. There was no cortisol effect on glycogen breakdown, suggesting that the activation of other pathways, including gluconeogenesis, are required to account for the increased glucose production. Epinephrine-mediated (10^-5M) glycogen breakdown and insulin-mediated (10^-8M) total glucose production were enhanced in hepatocytes of cortisol implanted sea ravens, but there were no change in any glucagon (10^-7M) effects. The enhanced glycogen breakdown in the absence of similar increases in total glucose production with epinephrine indicates mobilization of carbohydrate reserves for endogenous use by the liver. Food-deprivation for 8 weeks significantly decreased condition factor, plasma cortisol concentration and liver glycogen content in the sea raven, but had no effect on plasma glucose concentration. Hepatocyte total glucose production and flux rates from alanine increased significantly with food-deprivation. Moreover, food-deprivation increased responsiveness of total hepatocyte glucose production to the actions of glucagon and insulin, but not to epinephrine; none of these effects were modified by cortisol implantation. Our results indicate that cortisol in the sea raven exerts both a direct and an indirect or permissive effect on hepatocyte metabolism by modifying hepatocyte responsiveness to epinephrine and insulin stimulation. Cortisol implantation did not modify the effects of glucagon or food-deprivation in this species.     

Simulation and quantification of enrichment and retention processes in the southern Benguela upwelling ecosystem

Important environmental processes for the survival and recruitment of early life stages of pelagic fishes have been synthesized through Bakun's fundamental triad as enrichment, concentration and retention processes (A. Bakun, 1996, Patterns in the Ocean. Ocean Processes and Marine Population Dynamics. San Diego, CA, USA: University of California Sea Grant). This conceptual framework states that from favourable spawning habitats, eggs and larvae would be transported to and/or retained in places where food originating from enrichment areas would be concentrated. We propose a method for quantifying two of the triad processes, enrichment and retention, based on the Lagrangian tracking of particles transported within water velocity fields generated by a three‐dimensional hydrodynamic model. We apply this method to the southern Benguela upwelling ecosystem, constructing putative maps of enrichment and retention. We comment on these maps regarding main features of the circulation in the region, and investigate seasonal variability of the processes. We finally discuss the results in relation to available knowledge on the reproductive strategies of two pelagic clupeoid species abundant in the southern Benguela, anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Our approach is intended to be sufficiently generic so as to allow its application to other upwelling systems.     

Effects of capture,loading density and transport stress on the mortality,physiological responses,bacterial density and growth of rohu <Emphasis Type="Italic">Labeo</Emphasis><Emphasis Type="Italic"> rohita</Emphasis> fingerlings

This study evaluated the effects of three levels of loading density (200, 300 and 400 g L⁻¹) and four levels of duration (1, 3, 6 and 9 h) on the mortality, plasma cortisol and chloride levels and growth of rohu Labeo rohita fingerlings in a transport simulation. While total immediate mortality was low (4–12%), delayed mortality was high (27–49%). Initial capture and handling were found to constitute the most stressful phase as indicated by elevated plasma cortisol. The levels of cortisol continued to rise at 6 and 9 h after transport, with the highest level observed at 9 h after transport. The level of plasma chloride fell after transport across all density levels and treatment durations. Specific growth rate (SGR, %/day) and total bacterial density (cfu/g) were not different between and within treatments, and between treatments and the controls. This study demonstrates that transport has a profound effect on the stress responses of rohu fingerlings. Although the level of immediate mortality was low, the higher level of delayed mortality has serious implications in terms of production inefficiency for grow-out farmers.     

The effects of introduced tilapias on native biodiversity

• 1. The common name ‘tilapia’ refers to a group of tropical freshwater fish in the family Cichlidae (Oreochromis, Tilapia, and Sarotherodon spp.) that are indigenous to Africa and the southwestern Middle East. Since the 1930s, tilapias have been intentionally dispersed worldwide for the biological control of aquatic weeds and insects, as baitfish for certain capture fisheries, for aquaria, and as a food fish. They have most recently been promoted as an important source of protein that could provide food security for developing countries without the environmental problems associated with terrestrial agriculture. In addition, market demand for tilapia in developed countries such as the United States is growing rapidly.
• 2. Tilapias are well‐suited to aquaculture because they are highly prolific and tolerant to a range of environmental conditions. They have come to be known as the ‘aquatic chicken’ because of their potential as an affordable, high‐yield source of protein that can be easily raised in a range of environments — from subsistence or ‘backyard’ units to intensive fish hatcheries. In some countries, particularly in Asia, nearly all of the introduced tilapias produced are consumed domestically; tilapias have contributed to basic food security for such societies.
• 3. This review indicates that tilapia species are highly invasive and exist under feral conditions in every nation in which they have been cultured or introduced. Thus, the authors have concluded that, despite potential or observed benefits to human society, tilapia aquaculture and open‐water introductions cannot continue unchecked without further exacerbating damage to native fish species and biodiversity. Recommendations include restricting tilapia culture to carefully managed, contained ponds, although exclusion is preferred when it is feasible. Research into culture of indigenous species is also recommended.

Copyright © 2005 John Wiley & Sons, Ltd.