Oceanic biology: spawning of eels near a seamount

Discoveries of the larvae of the European and American eels, Anguilla anguilla and A. rostrata, in the Sargasso Sea and of the Japanese eel, A. japonica, in the Philippine Sea indicate that these freshwater eels migrate thousands of kilometres into the open ocean to spawn. Here we pinpoint a spawning location for Japanese eels after genetically identifying newly hatched larvae that we collected from the site. The restricted size of this spawning area ensures that the eel larvae enter a particular current that transports them to the freshwater areas in east Asia where they mature, and it also prevents them from being carried southwards away from their species range by a different local current.     

基于16S rDNA序列和RFLP分析的病鳗分离菌株鉴定

结合16S rDNA基因序列和限制性片段长度多态性(RFLP)的分析方法,通过与GenBank库中已递交的细菌16S rDNA基因序列进行同源性比较,对分离自发病鳗鲡(欧洲鳗鲡,日本鳗鲡和美洲鳗鲡)的30株细菌进行初步鉴定和分类.结果表明,这些细菌可大致分为气单胞菌属(Aeromonas sp.)、假单胞菌属(Pseudomonas sp.)、邻单胞菌属(Plesiomonas sp.)、克雷伯氏菌属(Klebsiella sp.)、柠檬酸杆菌属(Citrobacter sp.)、不动杆菌属(Acinetobacter sp.)和肠杆菌属(Enterobacter sp.)等7个菌属.分析认为,部分分离菌株可能是引起鳗鲡病害的疑似致病性菌株.     

Neotropical Africanized honey bees have African mitochondrial DNA

Non-indigenous African honey bees have invaded most of South and Central America in just over 30 years. The genetic composition of this population and the means by which it rapidly colonizes new territory remain controversial. In particular, it has been unclear whether this 'Africanized' population has resulted from interbreeding between African and domestic European bees, or is an essentially pure African population. Also, it has not been known whether this population expanded primarily by female or by male migration. Restriction site mapping of 62 mitochondrial DNAs of African bees from Brazil, Venezuela and Mexico reveals that 97% were of African (Apis mellifera scutellata) type. Although neotropical European apiary populations are rapidly Africanized by mating with neotropical African males, there is little reciprocal gene flow to the neotropical African population through European females. These are the first genetic data to indicate that the neotropical African population could be expanding its range by female migration.     

黄鳝的地理分布及起源的探讨

<正> 一、黄鳝Monopterus albus(zuiew)的地理分布黄鳝同黄蝉、黄(鱼旦)。又简名鳝鱼或(鱼单)鱼。山、陕亦名蛇鱼。两千多年前的山海经内就有“灌河之水其中多(鱼旦)”的记载。是我国人民习见和喜食的淡水鱼类之一。但迄今其地理分布尚无专文研究。不少文献称黄鳝分布于我国各处,或称除西北、西南外我国各处均产;但事实远非如此。据笔者研究在我国仅见于辽河下游;沿滦河向上约略过承德(海拔     

鳗鲡肝肾病病原菌的研究

从汕头地区3个养鳗场患肝肾病鳗鲡的肝脏和肾脏分离出60个菌株,用这些菌株人工感染鳗鲡能出现相同的症状,并能从肝脏或肾脏重新分离出相同的菌株,证实为该病的病原菌.这些菌株的形状基本一致,经鉴定为野生型迟呆爱德华菌(Edwardsiella tarda.wild type).这些菌株虽然是革兰氏阴性肠杆菌,但全部菌株对多粘菌素 E 高度耐药,对青霉素 G 反而较敏感.所有菌株对目前养鳗场常用的四环类抗生素及磺胺类药物高度耐药,其耐药率均达到100%,但对大多数被测试的抗菌药物敏感.     

鳝鱼静水无土养殖新技术

鳝鱼无土养殖可分为流水无土养殖和静水无土养殖两种类型。本文主要从鳝池的设计、苗种处理、日常管理等方面探讨了鳝鱼的静水无土养殖技术。     

鳗鱼和烤鳗中六六六,DDT残留量的气相色谱分析

本文用 HP5890气相色谱仪连电子捕获检测器,在Φ3mm×2m 涂以10%OV-17的色谱柱上分离测定了鳗鱼和烤鳗中六六六和 DDT 的残留量.12批样品的测定结果,检出率100%,六六六和 DDT 的总含量均小于0.1PPM.与文献报道的波兰、美国和意大利等某些水域的鳗鱼比较,污染程度要轻得多。     

The yellow sea green tides were dominated by one species, Ulva (Enteromorpha) prolifera, from 2007 to 2011

Green tides have occurred in the Yellow Sea successively from 2007 to 2011. Genetic analysis of the 5-year green-tide-forming algae needs to be performed to determine the source of the biomass and understand the mechanism of the green tide blooms. In this study, free-floating green algae were collected at different sites in the Yellow Sea in 2010 and 2011. Data on 182 free-floating samples and 155 attached Ulva samples from previous studies on the Yellow Sea green tides from 2007 to 2009 were also taken into consideration. Morphology observation and molecular phylogenetic analyses indicated that the Yellow Sea green tides were dominated by a single species, Ulva prolifera, from 2007 to 2011. Considering that at least five Ulva species inhabit the north coast of China, the unialgal composition of the green tides implied that (1) there may be some special physiology and propagation pathways of U. prolifera for its rapid expansion, (2) the mechanisms of the Yellow Sea green tide formation were similar for the last five years, and (3) the intra-species genetic variation and population structure of U. prolifera need to be studied to determine the exact origin of the bloom-forming biomass.     

雌雄异型异熟植物的开花机制研究进展

雌雄异型异熟是植物从雌雄同花向雌雄异株进化过程中的一种过渡类型,目前发现存在于13个科20个属植物中。其群体中包括雌先型和雄先型两种交配类型,两种交配类型植株的同步性和互不干扰性可有效地避免自交。一般认为雌雄异型异熟植株的交配类型是固定不变的,但也在一些植物中发现了彼此间的转化; 植株内雌雄花开放时间有的完全错开,有的部分重叠。经典遗传学认为交配类型受1对显/隐性的等位基因控制,且当群体达到平衡时两种交配类型的比例可达平衡状态(1:1),这在胡桃属和山核桃属上得到了验证,但在其他同类植物分子生物学方面的研究还是空白。雌雄异型异熟植物的性别决定为饰变型,其性别分化不仅受性别决定基因的遗传控制,而且还受植物激素的诱导调控,但不同植物上激素诱导性别分化的作用存在差异。解剖学研究表明同一交配类型上的雌雄花发育和成熟时间均存在差异。     

Evidence from mitochondrial DNA that African honey bees spread as continuous maternal lineages

African honey bees have populated much of South and Central America and will soon enter the United States. The mechanism by which they have spread is controversial. Africanization may be largely the result of paternal gene flow into extant European populations or, alternatively, of maternal migration of feral swarms that have maintained an African genetic integrity. We have been using both mitochondrial and nuclear DNA restriction fragment length polymorphisms to follow the population dynamics between European and African bees. In earlier reports, we suggested that if African honey bees had distinctive mitochondrial (mt) DNA, then it could potentially distinguish the relative contributions of swarming and mating to the Africanization process. Because mtDNA is maternally inherited, it would not be transmitted by mating drones and only transported by queens accompanying swarms. Furthermore, the presence of African mtDNA would reflect unbroken maternal lineages from the original bees introduced from Africa. The value of mtDNA for population studies in general has been reviewed recently. Here we report that 19 feral swarms, randomly caught in Mexico, all carried African mtDNA. Thus, the migrating force of the African honey bee in the American tropics consists of continuous African maternal lineages spreading as swarms. The mating of African drones to European queens seems to contribute little to African bee migration.     

Raptorial jaws in the throat help moray eels swallow large prey

Most bony fishes rely on suction mechanisms to capture and transport prey. Once captured, prey are carried by water movement inside the oral cavity to a second set of jaws in the throat, the pharyngeal jaws, which manipulate the prey and assist in swallowing. Moray eels display much less effective suction-feeding abilities. Given this reduction in a feeding mechanism that is widespread and highly conserved in aquatic vertebrates, it is not known how moray eels swallow large fish and cephalopods. Here we show that the moray eel (Muraena retifera) overcomes reduced suction capacity by launching raptorial pharyngeal jaws out of its throat and into its oral cavity, where the jaws grasp the struggling prey animal and transport it back to the throat and into the oesophagus. This is the first described case of a vertebrate using a second set of jaws to both restrain and transport prey, and is the only alternative to the hydraulic prey transport reported in teleost fishes. The extreme mobility of the moray pharyngeal jaws is made possible by elongation of the muscles that control the jaws, coupled with reduction of adjacent gill-arch structures. The discovery that pharyngeal jaws can reach up from behind the skull to grasp prey in the oral jaws reveals a major innovation that may have contributed to the success of moray eels as apex predators hunting within the complex matrix of coral reefs. This alternative prey transport mode is mechanically similar to the ratcheting mechanisms used in snakes--a group of terrestrial vertebrates that share striking morphological, behavioural and ecological convergence with moray eels.     

The cost of inbreeding in Arabidopsis

Population geneticists have long sought to estimate the distribution of selection intensities among genes of diverse function across the genome. Only recently have DNA sequencing and analytical techniques converged to make this possible. Important advances have come from comparing genetic variation within species (polymorphism) with fixed differences between species (divergence). These approaches have been used to examine individual genes for evidence of selection. Here we use the fact that the time since species divergence allows combination of data across genes. In a comparison of amino-acid replacements among species of the mustard weed Arabidopsis with those among species of the fruitfly Drosophila, we find evidence for predominantly beneficial gene substitutions in Drosophila but predominantly detrimental substitutions in Arabidopsis. We attribute this difference to the Arabidopsis mating system of partial self-fertilization, which corroborates a prediction of population genetics theory that species with a high frequency of inbreeding are less efficient in eliminating deleterious mutations owing to their reduced effective population size.     

褪黑激素在黄鳝体内分布与生殖季节性变化

选用处于不同性腺发育阶段的黄鳝,采用放射免疫技术测定了脑、眼、小肠、肝、肾、脾、心、皮肤和肌肉等组织以及血清中褪黑激素的含量．结果表明,褪黑激素在黄鳝体内的多数组织中存在（皮肤和肌肉除外）,其含量顺序为：眼＞全脑＞血清＞肝＞小肠＞肾＞脾＞心．黄鳝脑内,以下丘脑和垂体的褪黑激素水平最高,嗅叶、视盖与小脑居中,端脑及延髓最低．黄鳝体内各组织中褪黑激素水平皆显示出生殖季节性变化     

基于MHCⅡ类B基因的凹耳臭蛙(Odorrana tormota)种群遗传分化模式

利用II类MHC基因单基因座位Odto-A作为分子标记,对皖南山区凹耳臭蛙6个种群的遗传多样性和遗传分化进行研究.结果显示,皖南凹耳臭蛙总的基因多样性为0.812,核苷酸多样性为0.018.局域种群单倍型多样性变化范围为0.531-0.864,香溪种群单倍型多样性最高,最低的是漳河种群.与线粒体cyt b基因所揭示的单倍型多样性差别不大,但B基因的核苷酸多样性较之线粒体cyt b基因的高达一个数量级.暗示MHC基因丰富的核苷酸多态性可能与其病原体抗性多样性密切相关.分子变异分析结果显示,皖南山区凹耳臭蛙种群MHC II类B基因遗传变异主要来源于种群内,种群间发生了显著的遗传分化(Fst=0.05644,P=0.00391).成对种群间的遗传分化分析结果显示,直线距离最近的浮溪和香溪种群间也发生了显著的遗传分化,暗示这两个种群经历了不同的选择压力.受平衡选择的作用,MHC基因与基于中性分子标记所揭示的遗传格局不同,基于MHC基因的种群遗传分化与水系和直线地理距离均没有明显的相关性,而与种群所经历的选择压力密切相关.结果表明皖南凹耳臭蛙不同局域种群所经历的环境病原体的选择压力存在时空变异.     

Genetic evidence for the spread of agriculture in Europe by demic diffusion

European agriculture originated in the Near East about 9,000 years ago. The Neolithic reached almost all areas suitable for agriculture by 5,000 yr BP (before present). The routes and times of the spread of agriculture through Europe are relatively well established, but not its manner of spreading. This could have been by cultural diffusion with few genetic consequences. By contrast, Ammerman and Cavalli-Sforza proposed that the spread of farming increased local population densities, causing demic expansion into new territory and diffusive gene flow between the neolithic farmers and mesolithic groups. We have now tested observed genetic patterns against expectations derived from the demic expansion hypothesis. We found significant partial correlations of genetic distances with a distance matrix especially designed to represent the spread of agriculture on that continent, when geographic distances are held constant. These findings support the hypothesis of Ammerman and Cavalli-Sforza and invite further investigation into Renfrew's hypothesis on the origin of the Indo-European languages.     

常德稻田黄鳝感染胃瘤线虫的研究

研究了5月份沅水下游常德稻田所产黄鳝对胃瘤线虫幼虫的感染情况.结果表明,其感染率为77.3%,感染强度为6.08,平均丰度为4.70;黄鳝的感染与其自身的体长有一定关系,感染率在体长201-350mm范围内的黄鳝高达80%以上,感染强度在体长301-350mm范围内的黄鳝为最高(11.0个/尾),而体长大于350mm的黄鳝,其感染率和感染强度均有所降低,这可能与黄鳝对胃瘤线虫的感染产生免疫力有关;胃瘤线虫种群在黄鳝中呈聚集分布,其负二项参数k=0.9915;胃瘤线虫种群主要由体长41-60mm的个体组成.     

Sexual reproduction between partners of the same mating type in Cryptococcus neoformans

Cryptococcus neoformans is a globally distributed human fungal pathogen that causes life-threatening meningoencephalitis in immunocompromised patients. It has a defined sexual cycle involving haploid cells of alpha and a mating types, yet the vast majority of environmental and clinical isolates are alpha (ref. 3). Sexual recombination is normally expected to occur between isolates of opposite mating type in organisms with two mating types (or sexes). How sexual reproductive potential can be maintained in an organism with a largely unisexual, nearly clonal population genetic structure is unknown. One clue, however, is that alpha strains undergo fruiting, a process that resembles sexual mating but is thought to be strictly mitotic and asexual. We report here that hallmarks of mating occur during fruiting, including diploidization and meiosis. Pheromone response pathway elements and the key meiotic regulator Dmc1 are required for efficient fruiting. Furthermore, fusion and meiosis can occur between non-isogenic alpha strains, enabling genetic exchange. These studies reveal how sexual reproduction can occur between partners of the same mating type. These findings have implications for the evolution of microbial pathogens, as well as for parthenogenesis, cell fusion events and transitions between self-fertilizing and outcrossing modes of reproduction observed in both fungi and other kingdoms.     

基于CR及Cytb基因序列的大泷六线鱼野生群体遗传多样性分析

为进一步了解山东省内大泷六线鱼(Hexagrammos otakii)群体遗传背景和分化情况,合理保护与开发利用渔业资源,选取线粒体控制区(CR)和细胞色素b基因(Cytb)对分布于山东省近海沿岸的3个大泷六线鱼野生群体以及北黄海1个离岸大泷六线鱼野生群体的线粒体基因序列进行对比,分析它们的序列特征、遗传多样性和种群历史动态情况。经PCR扩增得到大泷六线鱼野生群体的CR和Cytb基因序列,全长分别为485bp和651bp。基于CR基因序列共检测到40个多态位点,单倍型多样性平均值为0.908,核苷酸多样性平均值为0.006,定义了53种单倍型。基于Cytb基因序列检测到56个多态位点,转换颠换比值为19.04,种内单倍型多样性平均值为0.934,核苷酸多样性平均值为0.005,定义了38种单倍型。对比分析表明,4个大泷六线鱼野生群体均具有高单倍型多样性和低核苷酸多样性。NJ系统进化树、群体间/内平均遗传距离、Fst值、基因流及AMOVA分析结果显示:山东省内近海沿岸大泷六线鱼野生群体和北黄海离岸野生群体遗传差异不显著,群体间存在频繁的基因交流,未形成显著的遗传分化。种群动态结果表明大泷六线鱼于更新世晚期经历了快速扩张,并形成了现有遗传格局。山东省内近海沿岸大泷六线鱼野生群体和北黄海离岸野生群体遗传结构之间不存在显著的地理隔离,这可能与人为增殖放流和秋冬季节黄海沿岸流及暖流有关,从而使得群体之间基因交流广泛。     

东海野生灰鲳mtDNA D-loop序列遗传变异分析

以东海区野生灰鲳背部肌肉的线粒体DNA为模板,采用PCR技术对7个个体的D-loop序列进行了扩增,通过对PCR产物进行双向测序,最终得到了471 bp的核苷酸片断(除去两端部分序列)。用DNAMAN6.0软件进行了排序比较发现,东海野生灰鲳的D-loop序列同源性高达99.48%;用DNASP4.0软件分析得知,7个序列共有6个单倍型(在GenBank登录号:GU970085-GU970087,GU970089-GU970091),在7个个体中,共检测到14个变异位点,包括13个转换和1个颠换位点。运用MEGA4.0软件计算出了不同个体间的遗传距离,并据此构建了MP和NJ系统树。用DNASP4.0软件计算出的多态位点数为14,核苷酸多样性指数和平均核苷酸差异数分别为0.009 71和4.571。研究结果表明,东海野生灰鲳的D-loop序列个体变异程度并不丰富。     

Analysis of genetic variation within and among <Emphasis Type="Italic">Ulva pertusa</Emphasis> (Ulvaceae,Chlorophyta) populations using ISSR markers

Ulva pertusa is a native species to Asia along the western coast of Pacific Ocean,with new occurrence records in the eastern coast of Pacific,the northwest coast of Atlantic and the Mediterranean Sea.However,little is known about its population genetic structure.In this study,twelve U.pertusa populations from 3 coastal areas of China:Qingdao,Yantai and Dalian,were applied to ISSR analysis.The selected 4 ISSR primers amplified 120 polymorphic bands totally.Nei's gene diversity (H) ranged from 0.0729 to 0.149...