Evidence of a local spawning site of marine eels along northeastern Japan, based on the distribution of small leptocephali

Evidence of recent spawning by several species of marine eels of the families Congridae, Ophichthidae, and Nettastomatidae was found over the continental shelf along the coast of northeastern Japan in October 2003. Sixty‐three leptocephali of at least three taxa that ranged from 3.8 to 12.3 mm total length were collected in a relatively small area, just to the south of Cape Shioya, primarily over the 100‐and 200‐m‐depth contours. The leptocephali of Gnathophis nystromi nystromi were the most abundant, followed by those of G. nystromi ginanago. This spawning area is located in an area that appeared to include water originating from the Tsugaru Warm Current and is further south than the typical latitude of the cold water of the Oyashio First Intrusion. These findings suggest that some species of marine eels may not migrate past the slope to spawn, and that the oceanographic features of the region may provide favorable conditions for the growth and retention of leptocephali in the area to the south of Cape Shioya.     

五倍子对鳗鲡致病性气单胞菌的体外抗菌后效应

采用试管液体二倍稀释法测定中药五倍子对鳗鲡养殖中致病性气单胞菌(威隆气单胞菌K17、肠棕气单胞菌G03、豚鼠气单胞菌R37和嗜水气单胞菌G06)的最小抑菌浓度(MIC).然后再采用菌落计数法分别测定五倍子在0.25、0.5、1、2、4倍于各菌MIC时对鳗鲡4株致病性气单胞菌K17、G03、R37、G06的体外抗菌后效应(PAE).结果显示:五倍子在0.25、0.5、1、2、4倍MIC值时对鳗鲡4株致病性气单胞菌均具有一定的PAE,且PAE与药液浓度在一定范围内(0.25～4倍MIC)呈剂量依赖性,当药液浓度达4倍MIC时,PAE明显延长(P＜0.05);五倍子对各致病菌株K17、G03、R37、G06的PAE值在1倍MIC浓度以上差异显著(P＜0.05),在4倍MIC时对于致病菌株K17和R37的PAE之间差异较小.结论:试验结果提示,在养殖鳗鲡病害防治中设计投药方案,选用中药五倍子治疗由致病性气单胞菌感染所造成的烂鳃、肝胆肿大、败血症等疾病时,除了考虑药代动力学和MIC指标外,还应考虑PAE因素,可适当延长给药间隔时间,降低药物对鳗鲡的副作用及对其摄食量和生长的负面影响.     

中国东南沿海日本鳗幼体的发育时相及其迁徙路径分析

对2008年1—3月采自中国广东至江苏沿海9个河口的534尾日本鳗鲡幼体鉴定发育时相,分析了其中104尾玻璃鳗的日龄、柳叶鳗龄和抵岸龄。结果显示,中国大陆东南沿海玻璃鳗的柳叶鳗龄平均为102(90~112)d,并呈现出地域性的从南至北逐步增大的趋势。Scheffe′s多重比较可将9个群体按柳叶鳗龄的大小归为3个组,南部的新会和汕头归为第1组;中间的福清、宁德、温州、台州归为第2组;北面的慈溪、九段沙和大丰归为第3组。同样,群体的R-聚类和个体的Q-聚类分析也显示出与上述分组相一致的结果。研究表明,从产卵场随北赤道洋流迁徙至菲律宾东北部并进入黑潮接近中国东南沿海的柳叶鳗,分成3个群体迁徙。变态最早的进入了南方的水域,抵达广东沿海;变态较早的进入了中部的东海水域,抵达闽浙沿海;变态最晚的则被送到长江口及其以北的沿海河口。结果还显示,最北部大丰的平均柳叶鳗龄[(106.00±3.22)d]比最南部新会的平均柳叶鳗龄[(91.87±1.36)d]大14.13 d,其与黑潮流速(约96 km/d)的乘积(1 350 km)同两地的距离大致相等,研究表明,我国沿海的玻璃鳗在柳叶鳗阶段是随着黑潮暖流自南向北被动地迁移。     

嗜水气单胞菌感染对美洲鳗鲡血液和生化指标的影响

为研究自发病美洲鳗鲡分离的嗜水气单胞菌对该鱼的致病性,试验将60尾美洲鳗鲡平均分为对照组、浸泡组和注射组3组,3组鳗鲡分别注射PBS、以1．0×10^8cfu／mL的嗜水气单胞菌浸泡和1．0×10^8efu／mL嗜水气单胞菌注射感染．各组鳗鲡分别于处理后6h和30h断尾采血并分离抗凝血和血清,抗凝血由血常规检测分析仪检测7项血液指标,血清由全自动生化分析仪检测13项与免疫相关的生化指标,数据用SAS软件进行统计学分析．结果表明,鳗鲡注射感染后6h,与浸泡组相比,血清谷草转氨酶（fiST）与谷丙转氨酶（ALT）的比值显著（P〈0．05）升高,其他指标在三组间均无显著（P〉0．05）差异．鳗鲡注射感染后30h,同对照组和浸泡组相比,血清总蛋白和血糖极显著（P〈0．01）下降,Na^＋和Cl^-浓度显著（P〈o．05）下降,而AST和ALT则均极显著（P〈0．01）上升．     

Bacterial diversity in various coastal mariculture ponds in Southeast China and in diseased eels as revealed by culture and culture‐independent molecular techniques

Mariculture ponds are widely distributed in Chinese coasts and have become a threat to the health of coastal ecosystems. In order to improve our understanding on the microbial composition in mariculture environments, we sampled a variety of ponds farming different animals or plants around the Dongshan Island and Xiamen Island in Southeast China and isolated cultures from the tissues of diseased eels. Analysis by polymerase chain reaction (PCR)‐denaturing gradient gel electrophoresis (DGGE), clone library and direct culturing methods revealed highly diverse bacterial communities in these samples. Bacterial communities in the Dongshan samples were dominated by Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. The Gracilaria verrucosa pond harbours the most abundant species (20 DGGE bands), followed by Epinephelus diacanthus pond (18 bands), Haliotis diversicolor supertexta pond I (18 bands) and Penaeus vannamei pond (11 bands). In comparison with surface waters, Penacus orientalis pond sediment showed a much more complex bacterial community, from which only sequences affiliated with Deltaproteobacteria, Firmicutes, Acidobacteria and candidate phylum TM6 were found. Bacterial cultures in diseased eels were closely related to two pathogenic genera, Aeromonas in Gammaproteobacteria and Bacillus, in Firmicutes. Clones affiliated with another two genera, Escherichia and Vibrio, that have pathogenic potentials were also identified. Phylogenetic analysis of a total of 131 sequences showed that 48.9% of the sequences were clustered into Gammaproteobacteria and formed the most abundant group, followed by Alphaproteobacteria (19.1%), Firmicutes (7.6%), Bacteroidetes (5.3%), Deltaproteobacteria (5.3%), Actinobacteria (4.6%), Chloroplast (3.8%), Acidobacteria (2.3%), Cyanobacteria (1.5%), Betaproteobacteria (0.7%) and TM6 (0.7%). 43.7% (28/64) of the phylogenetic clusters cannot be classified into any known genus and 44.3% (58/131) of the sequences show <95% similarity to public database records, suggesting that abundant novel species exist in mariculture ponds. Gathering bacterial diversity data in mariculture ponds and diseased fish is meaningful for the prevention and control of fish diseases and for the improvement of our understanding of microbial ecology in a pond environment.     

创伤弧菌ISCOMs疫苗对欧洲鳗鲡细胞免疫的影响

应用创伤弧菌ISCOMs疫苗对欧洲鳗鲡进行腹腔注射免疫,免疫后35 d进行攻毒试验,结果表明,经免疫的欧洲鳗鲡相对存活率达75%,证实创伤弧菌ISCOMs疫苗具有较好的免疫保护性。对创伤弧菌ISCOM疫苗免疫后的欧洲鳗鲡细胞免疫水平的淋巴细胞进行转化试验,检测结果分析表明,试验组与对照组的淋转指数差异不显著,推测该疫苗诱导的免疫保护方式可能与细胞免疫保护无密切相关性。     

Gonad histology and plasma steroid profiles in wild New Zealand freshwater eels (Anguilla dieffenbachii and A. australis) before and at the onset of the natural spawning migration. I. Females*

To determine steroid profiles in immature and maturing female eels from the wild, non-migratory and migratory New Zealand longfinned (Anguilla dieffenbachii) and shortfinned (A. australis) eels were caught and blood and ovarian samples collected. Plasma steroid levels were determined and related to the developmental stage of the ovary. Ovaries of non-migrants contained oogonia and previtellogenic oocytes. Vitellogenic oocytes were never observed in these groups, but instead were very common among migrants (up to 88% of oocytes). Concentrations of both androgens (androstenedione (AD), testosterone (T)) and estradiol-17 (E2) were higher in migrants than in non-migrants. Among migrants, T levels were higher in shortfins (2.27 ± 0.14 ng ml–1) than in longfins (0.82 ± 0.10 ng ml–1), whereas E2 levels were higher in longfins (mean 2.46 ng ml–1) than in shortfins. Levels of sex steroids were generally low in non-migrants. In contrast, plasma levels of 17-hydroxyprogesterone were significantly higher in non-migrants than in migrants. Similarly, cortisol levels were higher in non-migrating than in migrating shortfinned, but not longfinned, females. 17,20-Dihydroxy-4-pregnen-3-one, the putative maturation-inducing steroid in anguillids, was near minimum-detectable levels for all animals examined. Surprisingly, very high levels of 11-ketotestosterone (KT) were found in migrants, averaging nearly 3 ng ml–1 in longfins and over 20 ng ml–1 in shortfins. The identity of KT and several 5-reduced androgens was confirmed using gas chromatography - mass spectrometry. The function of KT in females is not known, but we suggest that this steroid hormone may play a role in preparing maturing animals for their spawning migration.     

Genetic structure of New Zealand eels Anguilla dieffenbachii and A. australis with allozyme markers

Abstract – Glass eels and adults of Anguilla australis and A. dieffenbachii were collected from rivers in the North and South Islands of New Zealand and tested for nine and ten allozyme loci, respectively. There was no heterogeneity among glass eel samples, but there was heterogeneity among adult samples within species. The results indicate that there may be single panmictic populations subject to sweepstake events or different selective pressures in the adult environments.     

分散固相萃取-气相色谱串联质谱法快速测定鳗鱼中7种农药残留量

建立了分散固相萃取-气相色谱串联质谱法快速检测鳗鱼中氟乐灵、三氯杀螨醇、克螨特等7种农药残留的分析方法。试样在乙腈提取时加入适量的去离子水和正己烷除去水溶性杂质和脂溶性杂质,再经中性氧化铝、C18和 PSA 混合粉末净化后用 GC－MS检测分析。采用选择离子扫描方式,外标法进行定量。该方法简便、快速,方法的检出限（S/N＝3）为0.002～0.01 mg/kg,在添加水平为0.01 mg/kg 时,平均回收率为80.7％～118％,相对标准偏差（RSD）为3.2％～6.4％;在添加水平为0.02mg/kg时,平均回收率为79.8％～114％,相对标准偏差（RSD）为3.3％～5.9％。