中国棘吻目棘头虫（棘头动物门：古棘头虫纲）的分类与分子系统学研究

Acanthocephala is one of the most important parasite groups of vertebrates, and many species are potential causative agents of disease in humans, domestic animals and wildlife. However, the present knowledge of the composition of the acanthocephalan fauna in China is far from complete. The current classifications of Acanthocephala are erected mainly on the basis of conventional taxonomy, which are dynamic and under continuous debate. The monophyly and systematic position of some its included order, family or genus-level taxa have not been definitely solved. In the present project, the taxonomy of Echinorhynchida (Acanthocephala: Palaeacanthocephala) in China will be performed using the integrated approaches including light and scanning electron microscopy, and sequencing and analysing ribosomal [small ribosomal DNA (18S), internal transcribed spacer (ITS) and large ribosomal DNA (28S)] and mitochondrial [cytochrome c oxidase subunit 1 (cox1), cytochrome c oxidase subunit 2 (cox2), cytochrome oxidase subunit b (cytb) and 12s rRNA gene] target regions, respectively. We can expect to determine the species composition of Echinorhynchida in China. Complementing conventional taxonomic work, molecular methods can help separate sibling species, to reveal cryptic diversity, to unambiguously identify larvae to species level, and to test the morphological variability of acanthocephalans belonging to intraspecific or interspecific variation. In addition, the phylogenetic analyses of some representative groups of Echinorhynchida based on different genes differing in their rate of evolution including the ribosomal 18S, ITS and 28S and the mitochondrial COI, COII, Cytb and 12S, respectively, will be accomplished. The objectives of our phylogenetic study are three-fold: (i) to test the monophyly of Echinorhynchida and its included families Echinorhynchidae, Rhadinorhynchidae and Illiosentidae. (ii) to solve the systematic position of some genus-level taxa of Echinorhynchida, i.e. Pomphorhynchus, Longicollum and Metechinorhynchus. (iii) to conjecture the evolutionary history of several morphological characters and evaluate the taxonomic importance of them in defining some family or genus-level taxa of Echinorhynchida. The results of this project have important implications for diagnosis, treatment and control of the parasitic diseases they cause, and are also extremely useful and helpful for fishery industry, animal husbandry and veterinary medicine, inspection and quarantine, and public hygiene.

棘头动物门是重要的动物寄生虫类群之一，可对人类和动物健康以及社会经济带来严重危害。然而我国棘头虫分类学研究基础薄弱，本底资源尚不清楚，一些目、科、属级分类阶元的系统地位仍然存在较大争议。本项目拟整合形态分类学方法与DNA分类学手段对我国棘吻目棘头虫进行系统的分类学研究，进一步摸清我国棘吻目棘头虫的本底资源和物种多样性情况，同时筛选适合物种分子鉴定的最优标记序列，初步构建中国棘吻目棘头虫分子鉴定数据库，解决形态分类学难于处理的表型变异的界定以及隐存种和幼体（棘头蚴/棘头体）鉴定等问题。此外，基于不同的分子数据，构建棘吻目代表类群的系统发育关系，重点解决棘吻目以及棘吻科、细吻科、斜棘科等科级阶元的单系性问题和泡吻属、长颈属、后棘属等属级分类阶元的系统地位问题，同时探讨一些常用形态特征的演化规律，评估其在不同分类阶元中的分类学价值，为重建符合自然进化规律的棘吻目棘头虫分类系统提供重要的理论依据。

棘头动物门是重要的动物寄生虫类群之一，可对人类和动物健康以及社会经济带来严重危害。然而，我国棘头动物门分类学研究基础薄弱，本底资源尚不清楚，一些目、科、属级分类阶元的系统地位仍然存在较大争议。本项目在四年的执行过程中，整合形态分类学方法和DNA分类学技术，共鉴定棘头虫11科18属43种，发现新物种11种，中国新纪录属1属、新记录种8种，并且对34种棘头虫的形态特征进行了重新描述和补记。首次测序得到11科18属33种棘头虫的相关核基因和线粒体DNA序列以及线粒体基因组数据。利用获得的相关分子数据，解决了新细吻属、泡吻属、长颈属等棘头虫类群在吻的形态与吻钩数目以及颈部形态存在显著的种内变异等问题，准确鉴定了一些类群的棘头蚴，揭示了一些形态种存在隐存种，解决了形态分类学方法无法解决的一些分类学难题，也为后续系统发育研究提供了重要数据支持。同时，研究表明核基因ITS序列和线粒体基因cox1序列在棘头虫物种分子鉴定以及种内变异和隐存种的发现方面具有明显优势，建议将其作为棘头虫分子鉴定的核心序列。.此外，整合不同分子数据，构建了棘头动物门代表类群的系统发育关系，研究结果表明原棘头虫纲是棘头动物门最原始的类群，否定了多棘头虫纲的有效性，证实了棘吻目、细吻科、四环科不是单系类群，支持多形目、泡吻科、中吻科、多形科是单系类群，厘清了斜吻科、中吻科、多形科以及多形科内不同属间的进化关系，支持恢复伪棘头虫科的有效性，揭示了长颈属是泡吻属的同物异名、球吻属是中吻属的同物异名。项目研究结果还提出多形科棘头虫在进化过程中经历了由寄生于陆生（淡水）食鱼鸟类，到寄生于海生食鱼鸟类，再到寄生于海洋兽类的寄生宿主转换模式假说。相关研究成果对于重建符合自然进化规律的棘头动物门分类系统具有重要的理论意义。