额尔齐斯河几种鱼类寄生三代虫种类鉴定及系统发育

对采自额尔齐斯河的银鲫(Carassius auratus gibelio Bloch)、东方欧鳊(Abramis brama orientalis Berg)、黏鲈(Gymnocephalus cernua Linnaeus)、金鳟(Oncorhynchus mykiss Walbaum)感染的三代虫(Gyrodactylus sp.)进行了研究, 通过几丁质结构的形态测量与比较, 初步鉴定寄生于银鲫的为细锚三代(G. sprostonae), 寄生东方欧鳊的为秀丽三代虫(G. elegans), 寄生黏鲈的为普氏三代虫(G. prostate), 寄生金鳟的为细鳞鲑三代虫(G. brachymystacis)。同时将测定的三代虫的ITS序列, 与GenBank上三代虫序列进行比对分析, 发现上述4种三代虫分别与细锚三代虫、秀丽三代虫、细鳞鲑三代虫、普氏三代虫的ITS同源性都在99.3%以上, 进一步验证了形态学的鉴定结果。系统发育分析显示细鳞鲑三代虫和细锚三代虫位于G. (Limnonephrotus)亚属的一枝, 秀丽三代虫和普氏三代虫位于G. (Gyrodactylus)亚属的一枝, 而此两亚属亲缘关系较远。     

铜鱼寄生三代虫一新种的记述

本文报道我国长江中游铜鱼鳃部寄生的三代虫一新种,即:铜鱼三代虫(新种)Gyrodactylus coreiusisp.nov.,新种的形态特征及其与相近种之间的差别在文中进行了描述和比较。     

金鱼寄生三代虫的形态学及基于rDNAits序列的分子鉴定

为查明我国金鱼三代虫的种类, 研究采用形态学与分子生物学相结合的方法, 对我国6个金鱼主要养殖区的三代虫进行了调查。通过形态测量分析, 发现了4种三代虫, 分别为: 小林三代虫（Gyrodactylus kobayashii）、G. gurleyi、G. longoacuminatus和三代虫未定种（Gyrodactylus sp.）。而通过核糖体rDNA its序列比对分析, 发现有2种三代虫分别与小林三代虫和G. longoacuminatus相似性在99.1%以上, 有1种与G. gurleyi的相似性在98.2%以上, 另外, 还有1种三代虫与现有序列的相似性都较低, 虽然它与小林三代虫的相似性最高, 也仅为91.0%, 暂为未定种。系统发育分析也显示, 金鱼寄生的3种三代虫分别与小林三代虫、G. gurleyi和G. longoacuminatus聚集在一起, 另外1种单独聚在一起, 这4种三代虫均隶属于G. （Limnonephrotus）亚属, 与G. （Gyrodactylus）亚属的秀丽三代虫（G. elegans）的亲缘关系很远。通过对三代虫样品的抽样调查发现, 小林三代虫存在于所有采样点, 在广州、武汉、郑州3个采样点为优势种, 所占的比率都在60%以上; G. gurleyi在海口、南京和上海为优势种, 所占的比率都在50%以上; G. longoacuminatus和三代虫未定种所占比率均较小。由此可见, 小林三代虫和G. gurleyi是我国金鱼常见的三代虫, G. gurleyi 和G. longoacuminatus是中国三代虫新记录种。       

鱼类三代虫研究进展

三代虫是一类常见的鱼类体表寄生虫,广泛寄生于各种鱼类,其危害近年有加剧之势,对鱼类养殖业造成较大威胁。本文从三代虫的分类方法、种群动态和引起寄主免疫反应等方面综述了鱼类三代虫研究现状及发展趋势。     

鱼类三代虫的寄主特异性分析

分析了迄今为止世界范围三代虫的寄主情况。三代虫具有很强的寄主特异性,并且在种、属及科等水平上的特异性均有较明显差异;分析同一种寄主上所寄生的三代虫种类之间的关系,显示大部分寄主只寄生一种三代虫,体现出了三代虫很强的寄主特异性。     

常用消毒剂次氯酸钠和二氧化氯对小林三代虫的杀灭效果

为了有效控制三代虫病, 实验以寄生于金鱼的小林三代虫(Gyrodactylus kobayashii)为动物模型, 研究了两种常用消毒剂次氯酸钠溶液(NaClO)和二氧化氯(ClO2)的杀虫效果。结果表明: 在离体(in vitro)条件下, 当NaClO的有效浓度0.2 mg/L或ClO2的有效浓度0.15 mg/L 时, 小林三代虫的平均存活时间均少于2h, 而对照组中小林三代虫的平均存活时间是20.8h。当ClO2的有效浓度0.15 mg/L时, 70%以上的虫体发黑, 而其他浓度处理组, 大部分虫体即使死亡, 虫体依然保持透明。在在体(in vivo)条件下, 当 NaClO的有效浓度0.2 mg/L或ClO2的有效浓度0.5 mg/L 时, 驱虫率都几乎达到100%, 并且驱虫率随着药物浓度的增加而提高,但当ClO2的有效浓度为0.6 mg/L时, 养殖水体出现了白色絮状物。在在体条件下, NaClO的驱虫效果好于ClO2。在金鱼的急性毒性实验中, NaClO和ClO2的安全浓度分别是0.18和0.48 mg/L, 仅稍低于其在在体条件下完全驱除小林三代虫的最小浓度(0.2、0.5 mg/L), 说明次氯酸钠溶液和二氧化氯在驱除三代虫时对金鱼不太安全, 因此, 在治疗金鱼的三代虫病时要慎使次氯酸钠溶液和二氧化氯。然而, 这两种消毒剂能否适用于其他鱼类三代虫病的治疗则有待进一步研究。     

基于线粒体控制区和微卫星标记探讨秦岭细鳞鲑物种有效性

文章基于线粒体控制区基因序列和微卫星标记比较秦岭细鳞鲑(Brachymystax tsinlingensis Li)、黑龙江流域的尖吻细鳞鲑(Brachymystax lenok Pallas)和钝吻细鳞鲑(Brachymystax tumensis Mori)的分子遗传差异,为澄清其分类地位争议提供分子证据。结果表明:(1)扩增217个样本的mtDNA D-loop区序列,共获得45个单倍型,类群间无共享单倍型;基于单倍型构建的系统进化树显示三个细鳞鲑类群呈独立的支系;(2)基于14个呈多态性位点的遗传分化结果表明,秦岭细鳞鲑与尖吻或钝吻细鳞鲑之间的遗传距离均大于尖吻细鳞鲑和钝吻细鳞鲑之间的遗传距离;(3)基于线粒体D-loop和多态性微卫星位点计算出的遗传分化系数(F_ST)都远高于0.25表明三个类群间的遗传分化程度极高。这些结果表明,秦岭细鳞鲑与黑龙江流域细鳞鲑之间遗传分化程度高,结合前期发现秦岭细鳞鲑与黑龙江细鳞鲑类群有明显形态分化的研究结果及它们之间地理隔离已久的现状,研究初步判定秦岭细鳞鲑为独立物种,并建议以Brachymystax tsinlinge...     

基于形态学差异探讨秦岭细鳞鲑亚种有效性问题

秦岭细鳞鲑(Brachymystax lenok tsinlingensis Li)的亚种分类地位自命名以来一直饱受争议。研究运用单因素方差分析、主成分分析、判别分析、聚类分析及差异系数检验法, 对秦岭细鳞鲑和黑龙江流域的尖吻细鳞鲑(B. lenok lenok)和钝吻细鳞鲑(B. tumensis)的5项可数性状和34项标准化后的比例性状进行统计分析。单因素方差分析结果表明, 尖吻细鳞鲑、钝吻细鳞鲑和秦岭细鳞鲑在32项比例性状和5项可数性状上存在极显著差异(P<0.01); 主成分分析结果显示, 贡献率较大的前3个主成分的累计贡献率为92.779%; 以逐步判别分析方法选用14个判别效果较好的比例性状构建了3个细鳞鲑类群的判别函数, 综合判别率为99.4%。基于欧式距离矩阵法构建的形态学聚类图显示, 秦岭细鳞鲑和尖吻细鳞鲑距离较近, 而与钝吻细鳞鲑距离较远。据Mayr 75%亚种识别和划分规则, 34项比例性状和5项可数性状中, 尖吻细鳞鲑和秦岭细鳞鲑第一鳃弓外鳃耙数目的差异系数大于1.28, 而钝吻细鳞鲑和秦岭细鳞鲑有31项比例性状和2项可数性状的差异系数高于1.28。据分析结果, 结合秦岭细鳞鲑地理隔离的事实及其与尖吻细鳞鲑和钝吻细鳞鲑的形态差异, 推断秦岭细鳞鲑与黑龙江流域内的尖吻细鳞鲑的形态差异程度至少已达亚种水平。     

寄生于洪湖经济鱼类鳃上的单殖吸虫包括二新种的描述

本文报告寄生于洪湖经济鱼类鳃上的单殖吸虫共60种,包括描述指环虫和三代虫各一新种,并有若干寄主新记录及长江流域新记录。     

鱼类三代虫分子生物学的研究进展

三代虫是一类常见的鱼类体外寄生虫,绝大多数种类寄生于鱼类的体表和鳃,大量寄生可导致苗种甚至成鱼大批死亡,或引起其他病原感染而致继发性鱼病,造成严重的经济损失.本文从三代虫目前的分类学概况、DNA分类学和条形码技术、核糖体基因及线粒体基因的研究等方面概述了鱼类三代虫分子生物学的研究现状,为三代虫及扁形动物的分子生物学研究及其应用提供有用的资料.     

Marked variation in parasite resistance between two wild populations of the Trinidadian guppy, Poecilia reticulata (Pisces: Poeciliidae)

This is the first study to demonstrate significant differences between two natural Trinidadian guppy populations in susceptibility to a pathogenic monogenean parasite, Gyrodactylus turnbulli . Following experimental infection with an isogenic laboratory culture of G. turnbulli , fish from the Upper Aripo (UA) lost parasites more slowly and carried up to three times as many parasites at peak infection than did those from the Lower Aripo (LA). The UA population appeared to be more susceptible than the LA fish, even though fish of both populations were naïve to this particular laboratory strain of G. turnbulli and had not encountered any gyrodactylid infection for at least 65 days. The parasite infection reduced the feeding response and feeding activity of UA and LA fish to a similar extent. Our findings suggest that this ectoparasite may have an important impact on the evolutionary biology of guppies (and possibly of other teleosts), particularly as the prevalence of Gyrodactylus infection in natural populations may be as high as 50%. We discuss the role of parasite infections on natural and sexual selection, the good genes model and the implications for immunogenetics in small genetically isolated host populations.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 645–651.     

Phylogeography and demographic history of Gyrodactylus konovalovi (Monogenoidea: Gyrodactylidae), an ectoparasite on the East Asia Amur minnow (Cyprinidae) in Central China

Gyrodactylus konovalovi is an ectoparasite on the Amur minnow (Rhynchocypris lagowskii) that is widely distributed in the cold fresh waters of East Asia. In the present study, the phylogeography and demographic history of G. konovalovi and the distribution of its host in the Qinling Mountains are examined. A total of 79 individual parasites was sequenced for a 528 bp region of the mitochondrial NADH dehydrogenase subunit 5 (ND5) gene, and 25 haplotypes were obtained. The substitution rate (dN/dS) was 0.068 and indicated purifying selection. Haplotype diversity (h) and nucleotide diversity (π) varied widely in the Qinling Mountains. Phylogenetic trees based on Bayesian inference (BI), maximum likelihood (ML), and maximum parsimony (MP) methods and network analysis revealed that all haplotypes were consistently well‐supported in three different lineages, indicating a significant geographic distribution pattern. There was a significant positive correlation between genetic differentiation (F_st) and geographic distance. The results of mismatch distribution, neutrality test and Bayesian skyline plot analyses showed that whole populations underwent population contraction during the Pleistocene. Based on the molecular clock calibration, the most common ancestor was estimated to have emerged in the middle Pleistocene. Our study suggests for the first time that a clearly phylogeography of G. konovalovi was shaped by geological events and climate fluctuations, such as orogenesis, drainage capture changes, and vicariance, during the Pleistocene in the Qinling Mountains.     

Speciation by host switch and adaptive radiation in a fish parasite genus Gyrodactylus (Monogenea,Gyrodactylidae)

Four hundred Gyrodactylus species have been formally described, but the estimated number of species in this fish ectoparasite genus of Monogenean Platyhelminthes is more than 20,000. The unusually high species richness has lead to the hypotheses of speciation and adaptive radiation via host switching. These hypotheses were tested by reconstructing a molecular phylogeny for the subgenus G. (Limnonephrotus) which is a group of freshwater parasites, including five species infecting wild and farmed salmonids. The highly variable ITS1 and ITS2 segments and the conservative 5.8S ribosomal gene were sequenced in 22 species plus two species representing the subgenus G. (Paranephrotus) as an outgroup. The phylogeny was compared with host systematics: the species were collected from six fish families (Cyprinidae, Salmonidae, Percidae, Esocidae, Gasterosteidae, and Gobitidae). The phylogenetic analysis demonstrated that G. (Limnonephrotus) is a monophyletic group that was originally hosted by cyprinids. The speciation has occurred in two episodes, the older one manifested in genetic distances 25-33% (4-6 Myr BP). The latter speciation burst occurred in one clade only, perhaps one million years ago. This clade has been morphologically identified as a wageneri species group. It is a monophyletic group of 18 species [studied here] and contains all five salmonid parasites, but also parasites, on cyprinids, percids, esocids, and gasterosteids. In G. (Limnonephrotus), eight host switches crossing the host family barrier were observed, and at least three of them were followed by repetitive speciation. Seven host-switch events were statistically confirmed by bootstrapping. The suggested model of speciation by host switch was accepted, and interestingly the adaptive radiation seems to be a consequence of host switch to a new family (key innovation model). The molecular and ecological evolution rate of Gyrodactylus parasites is manyfold in comparison to host species, and the phylogenies are largely independent and disconnected.     

Seasonal occurrence, topographical distribution and transmission of Gyrodactylus callanatis (Monogenea) infecting juvenile Atlantic cod in the Oslo Fjord, Norway

The seasonal occurrence and topographi0cal distribution of Gyrodactylus callanatis on three year-classes of juvenile Atlantic cod Gadus morhua , has been studied in the Oslo Fjord, Norway over a 2-year period. Both prevalence and abundance increased in spring and peaked in summer on the 1992 year-class and decreased in autumn. The highest intensities recorded in the study were observed on the 1992 year-class in June, with some fish harbouring more than 500 worms each. On the 1993 year-class, prevalence increased throughout the year, until it reached 100% in November; abundance, however, did not differ significantly between monthly samples, but intensities on individual fish were highest in June. The 0 + cod are probably infected when they immigrate to the nursery grounds in autumn and mingle with infected 1 + cod. About 74% of the worms infected the gill arches, oral cavity and pharynx, while 26% infected the body, head and fins. There was a significantly higher percentage of worms on the latter sites at intensities of less than 20 and more than 100 worms per fish. This is possibly related to the mode of transmission in G. callariatis . The initial infection sites are presumably the fins and head, and the most important route of transmission of G. callanatis is believed to be via the substrate. Other routes of transmission are also discussed.     

Susceptibility of brown trout to Gyrodactylus salaris (Monogenea) under experimental conditions

Brown trout ( Salmo trutta ) from anadromous River Lierelva, resident Lake Tunhovd, and resident Nordmarka stocks were exposed to Gyrodactylus salaris -infected salmon parr. The brown trout were fed pellets before the experiments, except for one group of the Nordmarka stock which was starved for 19 days before the experiments. The mean number of parasites declined directly and rapidly post infection for all groups of trout. There were no pronounced differences in resistance between the anadromous and the resident stocks. G. salaris infections tended to persist longer on starved than on fed trout of the Nordmarka stock. The maximum parasite persistence on trout was 50 days, and as parasite numbers increased on some fish parasite reproduction must have occurred on those trout. However, the limited susceptibility and marked innate resistance of trout to G. salaris establishment, development and reproduction, suggest parasite metapopulations will not survive on this species. Nevertheless, trout may still play a role in the dispersal of G. salaris within and between rivers.     

Host specificity dynamics: observations on gyrodactylid monogeneans

The directly transmitted viviparous gyrodactylids have high species richness but low morphological and biological diversity, and many species are recorded from only a single host. They therefore constitute a guild of species ideal for studies of the evolutionary significance of host specificity. The group has the widest host range of any monogenean family, being found on 19 orders of bony fish. However, individual species range from narrowly specific (71% of 402 described species recorded from a single host) to extremely catholic (Gyrodactylus alviga recorded from 16 hosts). Gyrodactylid-host interactions extend from 60 mya (G. lotae, G. lucii) down to 150 years (G. derjavini on Oncorhynchus mykiss). Co-evolution with the host is comparatively rare within the gyrodactylids, but host switching or ecological transfer is common, and has been facilitated by the mixing of fish strains that followed glaciation. In this review, we consider the factors responsible for gyrodactylid specificity patterns, using examples from our work on salmonid gyrodactylids including G. salaris, responsible for major epidemics on wild Atlantic salmon (Salmo salar) in Norway since 1975, and G. thymalli from grayling and G. derjavini from trout.G. salaris has a wide host range with highest population growth rates on Norwegian salmon strains. However, growth rates are variable on both host strains and species, because of the multitude of micro- and macro-environmental factors influencing parasite mortality and fecundity. A better predictor of performance is the proportion of fishes of a strain which are innately resistant to the parasite, a measure which is negatively correlated with the time to peak infection in a host strain. Population growth rate is also negatively correlated with age of infection; the initial rate, therefore, predicts best the suitability of a fish as host for G. salaris. The host response to gyrodactylids appears to be the same mechanism in all salmonids with innate resistance as one end of a spectrum, but influenced by stress and probably under polygenic control. Hybrid experiments show that performance of G. salaris on a host is heritable, and usually intermediate between that of the parents. This host response mechanism, coupled with the initial parasite population growth on a fish, determines the host specificity, i.e. whether the fish will be susceptible, a responder or innately resistant. The use of population growth rate parameters allows comparison of different hosts as a resource for a gyrodactylid. In the case of G. salaris, East Atlantic and Baltic strains of Atlantic salmon are core hosts, but other salmonids can physiologically sustain infections for considerable periods, and may be important in parasite dispersal and transmission. A further group of non-salmonid fishes are unable to sustain G. salaris reproduction, but can act as transport hosts.Population growth parameters are very labile to stressors and environmental factors, particularly temperature and salinity, and also other aspects of host ecology and water quality. These factors may also influence the spectrum of hosts that can be infected under particular conditions, and probably favoured ecological transfer of gyrodactylids between host species in periglacial conditions. G. salaris may still be undergoing post-glacial range expansion (aided by anthropogenic spread) as shown by the increase in the species range over the last 25 years. The origin of G. salaris, G. teuchis and G. thymalli is discussed in relation to glacial refugiums during the last ice age.     

Experimental infections of the monogenean Gyrodactylus turnbulli indicate that it is not a strict specialist

Parasites represent a threat to endangered fish species, particularly when the parasite can host switch and the new host is vulnerable. If the parasite is highly host specific then successful host switching should be a rare occurrence; however, the host range of many parasites which are assumed to be specialists has never been tested. This includes the monogenean Gyrodactylus turnbulli, a well-studied ectoparasite found caudally on its known host, the guppy, Poecilia reticulata. In this study, we monitored parasite establishment and reproduction on a range of poeciliids and more distantly related fish. Individually maintained fish were experimentally infected with a single parasite and monitored daily to establish whether G. turnbulli could survive and reproduce on other fish species. Gyrodactylus turnbulli can infect a wider range of hosts than previously considered, highlighting the fact that host specificity can never be assumed unless experimentally tested. Our findings also have significant implications for parasite transmission to novel hosts and provide further insight into the evolutionary origins of this ubiquitous group of fish pathogens. Previous molecular evidence indicates that host switching is the key mechanism for speciation within the genus Gyrodactylus. Until recently, most Gyrodactylus spp. were assumed to be narrowly host specific. However, our findings suggest that even so-called specialist species, such as G. turnbulli, may represent a threat to vulnerable fish stocks. In view of the potential importance of host switching under artificial conditions, we propose to describe this as 'artificial ecological transfer' as opposed to 'natural ecological transfer', host switching under natural conditions.     

陕西秦岭平河梁自然保护区小型兽类的组成与分布

2005年9月利用铗日法辅以陷阱法对位于秦岭山脉南坡东段的平河梁自然保护区及牛背梁自然保护区小型兽类进行了调查,共设置采集点10个;2460铗日中共捕获小型兽类689只,隶属于3目6科19属27种(另有两种鼢鼠和一种鼯鼠系其他手段捕获),平均捕获率28.01%。对捕获的27种小型兽类生态和垂直分布进行分析结果表明:平河梁保护区3个群落的Shannon-Weiner多样性指数在2.9288-3.3639之间,Pielou均匀性指数在0.7669-0.8602之间。在上述调查的基础上,结合前人对邻近地区的调查,据一些物种的分布特点,订出平河梁自然保护区小型兽类的名录,计48种,结果显示秦岭南坡东段小型兽类的物种多样性和丰富度要高于秦岭其他地区。另在考察中采集到白尾鼹(Parascaptor leucura)、小纹背鼩鼱(Sorex bedfordiae)、斯氏鼢鼠(Myospalaxsmithii)、川西白腹鼠(Niviventer excelsior),在秦岭山区尚属首次记录。还整理了秦岭南坡小型兽类名录,认为秦岭南坡有小型兽类55种,在动物地理区划上应属于西南区。     

太白虎凤蝶的生物学与生境研究

太白虎凤蝶Luehdorfia taibai主要分布于太白山南坡的局部地点,是我国特有种,种群数量稀少,并且呈下降趋势。研究了野生状态下该种蝴蝶的生活史、习性、生命表、产卵地需求,并对部分栖息地要素进行了调查分析。分析了濒危原因,提出了保护建议。太白虎凤蝶1年1代,以蛹越冬,蛹期约300d。翌年4月中下旬为成虫羽化盛期,产卵于幼虫寄主植物马蹄香Saruma henryi叶片背面。1—2龄幼虫聚集生活,3龄即扩散,白天藏入枯叶层中躲避天敌,晚上出来取食。老熟虫于枯叶或石缝中化蛹。产卵地多位于海拔1000—1400 m之间,森林郁闭度低于60%,寄主植物密度低于2株/m2,并且伴有较厚的枯叶层,较多石块的环境中。成虫访花、交尾活动和产卵地环境有所不同,多在沟底较为开阔、多蜜源植物的地点。对太白虎凤蝶的保护建议采取适度干扰原则,对栖息地生境定期实施矮林作业、割灌等经营管理措施,保持1个栖息地斑块内有几块较为开阔的林间空地和寄主植物和寄主植物即可。对于人为干扰过重的秦岭南坡地区,需进行人工管理恢复生境,辅以人工繁殖恢复种群数量。此外,应严格限制对太白虎凤蝶卵、幼虫和成虫的大量采集活动。