中国蛔总科分类修订与系统发育研究

Nematodes of the superfamily Ascaridoidea are important parasites of the alimentary tract of vertebrates and many species are potential causative agents of disease in humans, domesticated animals, and wildlife. However, our present knowledge of the composition of the ascaridoid nematode fauna in China is far from complete. The classification of Ascaridoidea was erected mainly on the basis of conventional taxonomy and we have not found a phylogenetic study of the whole superfamily Ascaridoidea that includes representatives of the worldwide fauna. This situation had a direct influence on the systematics of Ascaridoidea: the monophyly of some included family or subfamily-level taxa was challenging and the systematic position of Acanthocheilidae, Raphidascarididae, Goeziinae, Pseudanisakinae and their included genus-level taxa, for instance, Acanthocheilus, Ichthyascaris, Mawsonascaris, Maricostula, Goezia, Pseudanisakis had not been definitely solved for lacking reasonable phylogenetic analyses. The taxonomic definitions of some genera were thus questionable because of the uncertain taxonomic importance in defining different level taxa. In the present project, we will revise the taxonomy of Ascaridoidea in China mainly based on the traditional morphological methods. In addition, the phylogenetic analyses of Ascaridoidea based on morphological characters and molecular data including the ribosomal 18S, ITS and 28S genes and the mitochondrial 12S gene and COI, respectively, will be performed. The objectives of our phylogenetic study are three-fold: 1) to test the monophyly of the superfamily Ascaridoidea and some of its family or subfamily-level taxa. 2) to unravel the evolutionary relationships of Acanthocheilidae, Raphidascarididae, Goeziinae, Pseudanisakinae and their included genus-level taxa, with emphasis on the genera Acanthocheilus, Ichthyascaris, Mawsonascaris, Maricostula, Goezia, Pseudanisakis and their close-allied relatives. 3) to conjecture the evolutionary history of several morphological characters and evaluate the taxonomic importance of them in defining different level taxa. The results may provide important information for reconstructing the classification of the whole superfamily Ascaridoidea.

蛔总科线虫是人和动物体内重要的寄生虫类群，可对人类及动物健康和社会经济带来严重危害。然而，目前我国蛔总科线虫分类学研究还很薄弱，本底资源尚不清楚，蛔总科分类系统也存在较大争议，一些科、亚科、属的系统地位仍未解决，一些形态特征在不同属级阶元的分类学价值尚不明晰。本项目以经典分类学方法为主，辅以DNA分类手段对我国一些陆生脊椎动物和淡水鱼类寄生的蛔总科线虫进行分类修订。在此基础上，基于形态与分子数据，利用分支系统学与分子系统学手段，构建蛔总科代表类群的系统发育关系，检验当前蛔总科分类系统的合理性，重点解决棘唇科、哥泽亚科、伪尖亚科以及鱼蛔属、莫蛔属、肋蛔属等类群的系统地位的问题，同时探讨蛔总科常用的一些分类特征的演化规律，评估其在不同属级阶元中的分类学价值，进一步澄清阔肠属、蛇蛔属、葱肠属等类群的界定问题，为重建符合自然进化规律的蛔总科分类系统提供重要的理论依据。

蛔总科线虫是人和动物体内重要的寄生虫类群，可对人类及动物健康和社会经济带来严重危害。本课题在四年的执行过程中，先后赴海南省、广西省、云南省等10个省区，调查采集鱼类、两栖类、爬行类、鸟类及哺乳类寄生线虫标本2000余号，查清了一些重要经济动物感染蛔总科线虫的物种组成、感染水平和分布特征等基本情况。基于检视标本和已发表的文献资料，首次系统整理编写了中国蛔总科线虫物种名录（包括5科26属95种），并且对一些物种的分类地位进行了讨论和厘定。整合形态分类学方法与DNA分类学手段，发现报道蛔类线虫新物种4种、中国新纪录属2属、中国新纪录种3种，对31种蛔类线虫进行了重新描述和分类修订。首次测序得到18种蛔类线虫的核基因（包括18S、28S、ITS）和线粒体基因（包括12S、COI、COII）数据。.整合不同的核基因和线粒体基因序列，重建了迄今包括代表类群最全的蛔总科线虫系统进化树。研究结果支持将蛔总科分为六个单系的科级分类阶元。首次基于分子系统发育分析证实了棘唇科是一个有效的科，否定了伪尖亚科和哥泽亚科的亚科地位，支持异唇科是现存蛔总科中最原始的类群。明确了莫蛔属应该归入棘唇科、支持鱼蛔属、肋蛔属为独立的属，证实了宫脂属是一个多系类群，支持前盲囊属和弓首属具有较近的亲缘关系，均应归入弓首科。.此外，项目研究成果首次揭示蛔总科线虫最早起源于石炭纪早期的陆生四足类动物（约3.65–3.25亿年前），否定了以前被广泛接受的海洋起源假说。同时我们还发现蛔总科线虫在距今2.68–1.54亿年前的三叠纪时期经历了一次快速的辐射分化事件，提出海平面的剧烈变化可能是导致蛔总科线虫在三叠纪时期快速辐射分化重要原因的假说。项目的研究成果对于摸清我国蛔总科线虫的本底资源以及区系组成特点，研究蛔总科线虫起源与早期演化历史，重建符合自然进化规律的蛔总科线虫分类系统等方面都具有重要的理论意义。