【作者】 潘庭双；

【导师】 聂品；

【作者基本信息】 华中农业大学 ， 水产养殖， 2013， 博士

【摘要】 泡吻棘头虫是一类肠道内寄生虫,其终末宿主为鱼类。目前,全球已报道的泡吻棘头虫共有24种,在欧洲、亚洲、美洲、非洲和大洋洲都有分布。2010年7月,科研人员在我国新疆乌伦古湖(47°22’57.9"S；087°47’03.4"W)的东方欧鳊、高体雅罗鱼、鲤、鲫、丁(?)的肠道内发现了一种泡吻棘头虫,其感染率、感染强度(平均感染强度)分别为：26%、1-20(5)；60%、1(1)；100%、14-31(19)；60%、1-40(15)；25%、1-2(1.5)。经光学显微镜和扫描电镜观察,对其形态进行了详细的描述,命名为福海泡吻棘头虫。福海泡吻棘头虫躯干呈圆柱形,吻钩15-17纵列,每列9-12个吻钩；颈棒球杆状,颈部前缘、吻的后端形成一个大的球形泡；颈长与躯体长比值为0.5。两个吻腺大小几乎相等,末端逐渐变宽变粗。雄虫睾丸2个,前后排列；粘液腺6个,其后为2个粘液储存囊及1个薛氏囊；雄虫生殖系统长4.76-6.60mm(5.53),约占总体长的39-48%(42%)。卵梭形；子宫钟、子宫、阴道的长和宽分别为：378-540μm(475)×142-164μm(153)、1.93-2.40mm(2.12)×112-178μm(151)、220-428μm(336)×34-82μm(62)：雌性生殖系统长2.67-3.10mm(2.93),约占总体长的17-26%(20%)。近年来,课题组对报道于云南高原湖泊中的3种泡吻棘头虫进行采样,但均未获成功。本研究对分布于欧洲、北美以及我国的共5种泡吻棘头虫的16个不同地理种群的泡吻棘头虫线粒体基因组的序列、结构、多态性、系统发育及可能的起源与分化时间进行了分析。这16个泡吻棘头虫线粒体基因组均由36个基因组成,其中蛋白编码基因12个、tRNA22个、rRNA2个。这些基因均由线粒体同一条链转录而来,且排列方向一致。不同种类线粒体基因组的蛋白编码基因及rRNA排列顺序完全相同；但tRNA排列顺序略有不同,不同物种间有1-3个位置上的差异。泡吻棘头虫不同密码子使用频率各不相同,且同一种密码子在不同种泡吻棘头虫中使用频率亦不相同。这些泡吻棘头虫的线粒体基因组中,密码子使用最为频繁的是TTA、GGG、GTG;氨基酸使用最为频繁是Val、Leu、Gly。滑动窗口分析结果表明：完整线粒体核苷酸的多态性呈现多区域分布,atp6区域是仅次于非编码区的高变区,其次为nad2、rrnS等区域,cox3、nad1和cob部分区域亦存在较高水平的变异度。系统发育树和线粒体基因排列顺序均支持Pomphorhynchus laevis和Pomphorhynchus tereticollis是两个不同物种的观点；从英格兰采集到的P. laevis与欧洲大陆分布的P. tereticollis聚为一支,而不与欧洲大陆的P. laevis聚为一支,表明英格兰的P. laevis与P. tereticollis的亲缘关系更近；福海泡吻棘头虫与欧洲大陆P. laevis亲缘关系最近。依据松散分子钟理论,推测泡吻棘头虫最近的共同祖先存在于晚侏罗世,距今152.66Ma; Pomphorhynchus bulbocolli(?)(?)Pomphorhynchus rocci最近的共同祖先存在于晚渐新世,距今23.9Ma; P. laevis和P. tereticollis最近的共同祖先存在于早古新世,距今65.44Ma。此外,本研究还克隆了隐藏新棘虫的线粒体基因组。隐藏新棘虫是一种寄生于黄鳝肠道内的棘头虫。其线粒体基因组为双链环状,T、G、A、C含量分别为40.8%、28.8%、20.7%、9.7%。线粒体36个基因中,蛋白编码基因12个,tRNA22个,rRNA2个,所有基因均由同一条链转录。12个蛋白编码基因共由10,041个碱基组成(不包括终止密码子),编码3,347个氨基酸。3种最常使用的氨基酸分别是Val(15.84%),Gly(10.82%)和Ser(10.60%)(Serl:5.64%, Ser2:4.96%),这3种氨基酸占总氨基酸的37.26%。使用最频繁的3种密码子分别为：TTT (8.98%)、TTG (7.40%)、GTT (6.92%).22个tRNA碱基长度变化从49(trnD)至69(trnC),这包括个2个trnL和2个trnSo始新棘头虫纲的隐藏新棘虫与古棘头虫纲的Leptorhynchoides thecatus线粒体基因的排列顺序完全相同,但它们与原棘头虫纲的Oncicola luehei有2处相邻的tRNA发生了位置交换,这2处tRNA分别为trnK, trn及trnS1、trnM。系统发育表明,始新棘头虫纲与古棘头虫纲聚为一类,这一类再与原棘头虫纲聚为一大类；棘头动物门3个不同的纲聚为一类后,再与轮虫蛭态目聚为一大类,这一大类再与轮虫单巢目形成姊妹群。然而,对棘头虫不同类群的亲缘关系,以及与不同类群轮虫的亲缘关系的阐明还有待更多的研究。更多还原

【Abstract】 Acanthocephalans in the Pomphorhynchus are endoparasitic in fishes, with a total of24species recognized widely in literature. Species of Pomphorhynchus have been reported from plates of Pacific Ocean, Eurasia, Indian Ocean, Africa, and America.Pomphorhynchus fuhaiensis n. sp. was collected from the middle and posterior intestine of Abramis brama orientalis, Leuciscus idus, Cyprinus carpio, Carassius carassius and Tinca tinca, from Ulungur Lake (47°22’57.9"S;087°47’03.4"W) in Xinjiang Uygur Autonomous Region of China.6of23(26%) A. brama orientalis were infected with1-20(5) worms each,3of5(60%) L. idus infected with1(1) worms,4of4(100%) C. carpio with14-31(19) worms,3of5(60%) C. carassius with1-40(15) worms,2of8(25%) T. tinea with1-2(1.5) worms. Trunk almost cylindrical, enlarged in the middle, possessing15-17longitudinal rows of each9-12hooks (rarely9,10). Proboscis armature nearly equal in both sexes. Neck (between proboscis and trunk) is clavate, tapered and broader at base, forming a large round symmetrical bulb, posterior to proboscis. Proboscis receptacle extends through the neck and into the trunk. Mean neck:body ratio is about0.5. Lemnisci are equal, claviform, broader posteriorly, and extending beyond proboscis receptacle. Testes pre-equatorial, nearly equal, ovoid-spheroid, usually contiguous. Six pyriform cement glands are fusing posteriorly into2common cement reservoirs. Saefftigen’s pouch just posterior to cement glands, male reproductive system4.76-6.60(5.53) mm long, occupying39-48%(42%) of total length. Eggs are fusiform, with polar prolongation. The length and width of uterine bell, uterine, vagina are378-540(μm (475)X142-164μm (153);1.93-2.40mm(2.12)×112-178μm (151);220-428μm (336) X34-82μm(62). Female reproductive system occupying17-26%(20%) of total length.The complete mitochondrial (mt) genomes of5species in the Pomphorhynchus, representing16geographical populations, were obtained by common PCR and long PCR. These genomes are circular, double-stranded DNA molecules. All of these mt genomes have12protein coding genes, and there is some similarity among the amino acid sequences of these genes. Two rRNAs have the same arrangement in the mt genomes, but the22tRNAs differ in the arrangement among the mt genomes. All the36genes are coded in the same strand. Codon usages are different in different species of Pomphorhynchus. The most frequently used codons in Pomphorhynchus are TTA、 GGG、 GTG. Amino acid usages are also different, with the most frequently used amino acids being Val, Leu, Gly. The nucleotide polymorphism of the complete mt genomes is distributed in multi-region by sliding window analysis. The nad5and atp6are among the highest mutation region except the noncodig region, and the nad2and rrnS have a high level of mutation, with relatively high level also found in part of the cox3, nad1and cob.Phylogenetic analysis on the basis of these mt genomes indicates that Pomphorhynchus laevis and P. tereticollis should be considered as separate species. P. laevis collected from continental Europe was clustered in a same branch, but P. laevis collected from England was clustered in a same branch with Pomphorhynchus tereticollis from the continental. P. fuhaiensis had a close relationship with P. laevis from continental Europe. The origin and divergent time of species in the Pomphorhynchus were estimated by BEAST1.4.6. The origin of common ancestor of Pomphorhynchus was in late-Jurassic, being about152.66Ma before. Pomphorhynchus bulbocolli and P. rocci were diversified in late-Oligocene, about23.9Ma before; P. laevis and P. tereticollis diversified in early-Paleocene, about65.44Ma before. However, other Pomphorhynchus species should be included in the phylogenetic analysis in order to illustrate the clear phylogenetic relationship of species in the genus and their diversification.The complete mt genome of Pallisentis celatus is a circular, double-stranded DNA molecule (13,855bp). The nucleotide composition of the entire P. celatus mt genome sequence is40.8%T,28.8%G,20.7%A, and9.7%C and the overall A+T content is61.5%. The mt genome contains36genes including12protein coding genes,22tRNAs and2rRNAs (rrnL and rrnS), with all genes encoded in the same strand. The total length of the12protein coding genes is10,041bp, which consist of3,347codons, with the exclusion of termination codons. Analysis of the codon usage of the12protein coding genes revealed that three codons are used frequently. The TTT codon is used most frequently (8.98%), followed by TTG (7.40%) and GTT (6.92%). The most frequently encoded amino acids include Val (15.84%), Gly (10.82%) and Ser (10.60%)(Serl:5.64%, Ser2:4.96%), accounting for37.26%of total amino acid components.22tRNAs encoded by the mt genome of the P. celatus, vary in length from49(trnD) to69(trnC) nucleotides, including two trnL and two trnS.Comparison of the gene order in P. celatus with those in Leptorhynchoides thecatus and O. luehei reveals that P. celatus has identical gene arrangement with L. thecatus, and has almost identical gene arrangements with Oncicola luehei, with the only difference being the two reciprocal translocations of tRNAs between trnK and trnV, and between trnSl and trnMthat are directly adjoined to each other, respectively. Phylogenetic analysis based on36species of complete mt genome sequence data were obtained in BI and ML analyses with Montastraea annulari (Cnidaria) as an outgroup. Three acanthocephalan species, P. celatus, L. thecatus and Oncicola luehei form a clade with high nodal support, among which, P. celatus and L. thecatus form a clade, and then with O. luehei. Acanthocephala is much more close to Bdelloidea than to Monogononta, froming together a clade of Syndermata. However, further analyses in respect of genetic relationship of acanthocephalans and their relationship with rotifers should be carried out with more species of acanthocephalans representing different taxonomical groups.更多还原