褶纹冠蚌防御素基因特征与表达

褶纹冠蚌(Cristaria plicata)样本壳长(9.50±1.05) cm、壳高(6.45±0.81) cm, 暂养1周。40只随机分成试验组和对照组, 每组20只。用Trizol 法提取经诱导刺激后0、6、12、24、36、48 h的血液、外套膜、鳃、肝胰腺组织RNA, 构建褶纹冠蚌cDNA文库并从中获得防御素基因cDNA全长序列。结果表明, 褶纹冠蚌防御素序列全长为514 bp, 其中5’ UTR 有57 bp; 3’ UTR 有242 bp, 含有一个poly(A)尾; 开放阅读框长度为192 bp, 编码63个氨基酸组成的蛋白质, 该蛋白N端为1个由23个氨基酸构成的信号肽, 成熟肽由40个氨基酸组成, 理论等电点为8.72, 分子量为7.13 kD。三级结构预测显示其由一个 α 螺旋和两个 β 折叠片组成, 形成典型的CSαβ结构。通过注射10⁹ cell/mL 的嗜水气单胞菌(Aeromonas hydrophila)刺激褶纹冠蚌, 半定量分析PCR对褶纹冠蚌血液、外套膜、鳃和肝胰腺组织的防御素基因表达, 结果表明, 诱导前防御素基因在外套膜组织中表达量最高, 约为血液和鳃的1.25倍, 肝胰腺次之。在诱导0、6、12、24、36、48 h后, 对照组的防御素基因表达量在血液和鳃中无明显变化, 而在外套膜和肝胰腺中则呈现先略有下降而后上升; 试验组防御素基因在血液中 12 h 时表达量最高, 随后略有下降, 而在外套膜、鳃和肝胰腺组织中表达量均在 0 h 时出现峰值, 而后呈现下降趋势; 外套膜和鳃的表达量分别在 24 h 和 36 h 略有上升。本研究通过分析褶纹冠蚌防御素基因全序列, 并利用嗜水气单胞菌对褶纹冠蚌进行注射感染, 探讨防御素基因的表达规律, 以期为防御素对贝类非特异性免疫的影响提供基础依据。

     

胭脂鱼听觉阈值研究

利用听性脑干反应技术, 研究了胭脂鱼(Myxocyprinus asiaticus)的听觉阈值。通过插入皮下的电极记录了10尾胭脂鱼的短纯音听觉诱发电位。结果显示, 在系统最大声强下, 胭脂鱼的听频范围为100~5 000 Hz, 其中对100~2 000 Hz的声音敏感度较高, 最敏感的频率为800 Hz, 听觉阈值约为69.8 dB。随着声强的减小, 胭脂鱼的听性脑干反应波形最大, 振幅减小, 潜伏期延长。将10尾胭脂鱼的阈值平均, 得到了胭脂鱼的听性脑干反应听力图。胭脂鱼的听力图呈“U”形, 属于典型的动物听力曲线。研究胭脂鱼的听觉阈值对胭脂鱼物种保护具有重要意义, 同时可为评估噪声对胭脂鱼的影响提供数据支持。

     

不同温度和体质量对南海野生真蛸呼吸和排泄的影响

采用室内封闭静水式呼吸代谢实验装置, 开展不同水温梯度、不同体质量的南海野生真蛸(Octopus vulgaris)的呼吸代谢实验, 分析了不同水温条件下真蛸耗氧率和排氨率的变化, 不同体质量真蛸耗氧率和排氨率的变化, 以及真蛸呼吸代谢底物O:N比的变化。结果表明, 水温变化对南海野生真蛸耗氧率和排氨率有明显影响, 体质量对耗氧率和排氨率的影响不显著(P<0.05)。在16~32℃实验水温范围内, 不同水温梯度下, 相同体质量南海野生真蛸耗氧率及排氨率呈现先升高后降低的趋势; 相同水温条件下, 随着个体体质量的增加, 南海野生真蛸的耗氧率和排氨率虽有缓慢下降但不明显(P>0.05)。24℃可能为南海野生真蛸呼吸代谢的转折点, 在该水温下, 其耗氧率和排氨率最高, 代谢速率最快, 单位体质量真蛸的耗氧率和排氨率分别为0.86 mg/(g∙h)和36.69 μg/(g∙h)。真蛸呼吸代谢底物分析结果中, 在24~28℃水温变化范围内, O:N比不断增加, 表明真蛸呼吸消耗的能量中蛋白质供能比例不断降低。

     

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。

     

建鲤催乳素受体基因全长cDNA的克隆、序列分析与组织表达

为了解催乳素受体(Prolactin Receptor, PRLR)的基因序列及其在建鲤(Cyprinus carpio var. jian)渗透调节组织中的表达情况, 采用同源克隆和末端快速扩增(rapid amplication of cDNA ends, RACE)的方法分离克隆了建鲤PRLR基因全长cDNA, 得到2 440 bp的全长cDNA, 包括1 821 bp的开放阅读框(ORF), 213 bp的5′末端非编码区(UTR)以及406 bp的3′末端非编码区(UTR)。对该基因序列和推测的氨基酸序列进行同源性比对和系统分析显示: 建鲤与其他硬骨鱼类该基因的氨基酸序列相似度在37.46%～87.25%, 与鲤(Cyprinus carpio)的氨基酸相似度最高(87.25%), 鲫(Carassius auratus)次之(86.86%), 和金头鲷(Sparus aurata)的相似度较低(41.87%), 和人(Homo sapiens)最低(37.46%), 表明不同物种间的PRLR的氨基酸序列具有较高的保守性。用实时定量PCR (RT-PCR)检测该基因在建鲤脑、肠、鳃、性腺、肝、脾、肾、皮肤中催乳素受体的相对表达量, 其中鳃、肾、肠3个主要渗透调节组织的表达量较高, 这表明建鲤的渗透调节组织是PRLR的主要表达场所, 从定量角度提示了催乳素(prolactin, PRL)通过PRLR的表达, 作用于渗透调节组织从而行使其渗透压调节功能。本研究旨在为进一步探索建鲤的渗透调控机制提供基础依据。

     

福建省东山湾生态环境中滴滴涕(DDTs)的分布特征及风险评价

 根据2011年春季(5月)和夏季(8月)对东山湾生态环境的调查资料, 初步探讨了东山湾海水、沉积物和养殖贝类体中滴滴涕(DDTs)残留水平、分布趋势和组成特征, 并对东山湾生态环境中DDTs污染状况及其生态风险进行了评价。结果表明: (1)春季(5月)和夏季(8月)东山湾表层海水中DDTs质量浓度范围分别为ND~25.7 ng/L和ND~36.7 ng/L, 平均值分别为(6.08±3.02) ng/L和(16.30±4.78) ng/L; 底层海水中DDTs质量浓度范围分别为ND~30.6 ng/L和ND~36.7ng/L, 平均值分别为(7.75±2.07) ng/L和(13.30±5.12) ng/L, 总体上, 东山湾海水中DDTs浓度分布呈夏季高于春季、近岸高于远岸、由湾内向湾外下降的格局。与国内其他海湾相比, 东山湾海水中DDTs污染处于低水平状态, 但邻近漳江入海口海域的DS03站和DS11站可能有新的污染源输入。(2)东山湾表层沉积物中DDTs含量范围5.56~12.80 μg/kg, 平均值为(9.00±5.34) μg/kg, 总体上呈现由湾内向湾外下降之势, 东山湾表层沉积物中DDTs残留可能对生物产生负效应, 毒性风险为25%~75%。(3)东山湾海域养殖贝类DDTs的残留量在种类间存在一定的差异, 其DDTs含量范围在1.68~26.60 μg/kg, 平均值为15.70 μg/kg, 污染指数范围在0.007~2.660, 均值为1.580, 超标率达到71.4%, 超标倍数最高达1.66倍, 说明东山湾部分贝类受到DDTs的污染。

     

基于线粒体COI基因序列的5种鲤养殖品种遗传多样性研究

本研究通过对5个鲤养殖品种即高寒鲤(Cyprinus carpio Frigid carp)、松浦鲤(Cyprinus carpio Songpu carp)、蓝鳞鲤(Cyprinus carpio blue var)、松浦镜鲤(Cyprinus carpio Songpu mirror carp)和红镜鲤(Cyprinus carpio Red mirror carp)的线粒体COI基因部分序列的测定, 比较并分析了其遗传多样性和系统进化关系。在5个鲤品种共100个样本的线粒体COI序列中检测到8种单倍型, 其中5个单倍型(H1、H2、H4、H5、H6)涵盖样本较多, 占总样本数的94.06%。蓝鳞鲤的单倍型数最少, 仅有1个, 红镜鲤单倍型数为2个, 其余3个品种的单倍型数均为5个。5个品种单倍型多样性(H_d)在0.160±0.070~0.811±0.055, 其中, 遗传多样性最高的为高寒鲤。AMOVA结果表明, 品种间变异(50.28%)略高于品种内变异(49.72%), 各品种间的F_ST值在0.711 4~0.831 2, 其中蓝鳞鲤与其他群体之间差异最大。用MEGA4.0软件构建的基于遗传距离的进化树表明, 5个养殖品种中, 高寒鲤和红镜鲤的遗传距离最近(D=0.31), 聚为一支; 松浦镜鲤和松浦鲤的遗传距离较近(D=0.33), 聚为一支; 蓝鳞鲤与其他品种存在较大遗传差异, 单独形成一个分支。除蓝鳞鲤外, 其余4个养殖品种间均存在共享的单倍型(H2、H4、H5、H6), 可能是由于其在选育过程中亲本的遗传背景存在交叉, 同时也证明DNA条码在分析种内品种间遗传关系时具有可行性但具有一定的局限性。

     

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。

     

重组激活基因(RAGs)功能机制及其在鱼类早期发育中的作用

在B淋巴细胞和T淋巴细胞的发育过程中, BCR和TCR基因座(Igκ、Igλ、Igh、Tcrα、Tcrβ、Tcrγ、Tcrδ)的可变区(V)、多样区(D)、链接区(J)发生V(D)J重排, 该重排过程是在重组激活蛋白(RAG-1和RAG-2)的作用下完成的, V(D)J重排机制使机体拥有庞大的抗体库, 以应对自然界中多元的病原微生物。RAGs结构分为核心区和非核心区, 核心区域发挥着重要的基因片段酶切功能, 而非核心区域的九聚体序列(nonamer)、锌指等结构具有调节V(D)J重排的功能。RAGs的功能在转录水平、染色体水平以及蛋白水平受到严格的时间和空间调控, 以保证B/T细胞的正常发育。随着国内外学者对哺乳动物RAGs基因的结构与功能机制的深入研究, RAGs也在淡水鱼和海水鱼中有了越来越多的报道。由于RAGs的功能特点以及在进化过程中的稳定性, 其已成为研究鱼类免疫系统发育过程和系统进化的重要分子标记。本文在赤点石斑鱼 (Epinephelus akaara) RAGs研究的基础上探讨了RAGs定位鱼类免疫系统的发生过程, 旨在为鱼类人工繁殖技术的突破、鱼类疫苗的开发与研制以及鱼类免疫学研究等提供理论借鉴。

     

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.     

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.     

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.     

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.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.