福建滨海湿地固着缘毛类原生动物的分类学与分子系统学

Sessile peritrich protozoa is a large group of widespread and highly diverse organisms, which plays an important role in many fields, e.g. environmental ecology, aquaculture disease control, and wastewater treatment. Most studies on sessile peritrichs were carried out either from seawater or freshwater, while only few investigations were performed from brackish water habitat. In China, studies on sessile peritrichs were focused mostly on seawater habitat in high latitude regions or freshwater, while our understanding of the group from coastal area in southern part is quite limited. Till now, about 1,000 sessile peritrich species have been reported, however most species were identified based on living morphology only which makes their identification highly questionable. In the meantime, molecular information were available in less than 100 species which constrain the progress in elucidating phylogenetic relationships among sessile peritrichs. In this proposed project, samples will be collected from coastal wetlands in Fujian, among which the estuaries of Zhangjiang and Jiulongjiang rivers will be most investigated regions. The morphology of sessile peritrichs will be studied using modern taxonomic methods including both in vivo observation and silver staining. The phylogenetic relationship of sessile peritrichs will be assessed based on combined datasets, which contain information from morphology, morphogenesis, and multiple genetic markers of both nuclear and mitochondria. This proposed project will build a foundation for eventually taxonomic revision and phylogenetic analysis of the entire group of sessile peritrichs. It will require inclusion of samples from understudied genera and families in phylogenies, strengthening knowledge of sessile peritrich evolution at different taxonomic levels and it will also contribute to species diversity and gene database of sessile peritrichs by including freshly collected samples from a variety of habitats in Fujian coastal wetlands in a single systematic study.

固着生缘毛类为分布广泛、种类繁多的一大类纤毛虫原生动物，在环境生态、水产养殖、污水处理等领域具有重要的研究意义。当前围绕该类群研究的突出问题为（1）区系研究不均衡：国际间对该类群研究集中于海、淡水生境，对半咸水生境鲜有报道；（2）基于现代手段的研究严重缺乏：国际间该类群已报道近千种，但具银染信息种类不足300种，而具有分子信息种类仅数十种。本工作拟以福建漳江口、九龙江口等滨海湿地为研究区域，采用活体观察与银染等现代手段，展开对上述生境中固着缘毛类的分类学研究；在此基础上，以核与线粒体多基因为分子标记，开展对迄今不详类群的分子系统学研究，并结合形态、形态发生信息，完成系统树的构建、进化关系的梳理及不明类群的系统定位。从而填补我国南方海区该类群多样性研究的空白，为环境生态及相关领域工作提供重要的基础信息，同时为该类群进化-演化研究提供新的理论支撑，并为国际基因库信息积累做出一份建设性的贡献。

固着缘毛类原生动物隶属于纤毛门、寡膜纲、固着目。该类群成员个体微小、分布广泛，是水体尤其是富营养化水体中的优势类群。因此，该类群在系统发育与进化、环境生态等领域均有重要的研究意义。由于基于现代手段所开展的分类学工作严重缺乏，导致以此为基础的分子系统学研究仍存在诸多空白与未知。此外，区系研究的不平衡是该类群分子系统学研究的另一大障碍，该问题在河口区为代表的滨海湿地环境中尤为突出。在此背景下，有了本项目的提出。在过去的四年里，本项目聚焦福建九龙江河口区域，对全盐度区域进行为期一年的系统采集，利用现代分类学研究手段开展分类学研究，在此基础上，结合分子标记、形态学与生境等信息，重构固着缘毛类的系统发育树，对所涉种类/类群的亲缘关系进行系统地梳理，并对不明类群进行准确的系统定位。本工作结果如下：i）进行了全年、全盐度区域（包括淡水、寡盐、中盐、多盐区域）的样品采集，对检获固着缘毛类进行现代分类学分析的基础上，揭示了河口区该类纤毛虫的多样性，并给出该类群沿河口区全盐度的分布特征，即缘毛类为淡水/寡盐区域的优势类群，沿盐度增加逐渐减少，在海水端最低；ii）为进一步分析河口区固着缘毛类的系统进化关系，结合寄生生境、开阔大洋序列以及Genbank中近全长序列，构建了信息最为全面的系统发育树。与依据经典形态学所构建系统关系相反，固着缘毛目下多科级、属级阶元并非单元发生；iii）Astylozoidae进化支内囊括种类的多样性非常高，且其成员对环境具有极强的适应能力; iv）祖征重建分析揭示了在长期进化史中，固着缘毛类起源于淡水，并从淡水向咸水、海水甚至高盐水扩展。该项目所取得的研究结果较大程度上改写了原有基于经典形态学所建立的系统关系，为突破性结果。同时，为环境生态及相关领域工作提供了重要的基础信息，为该类群国际基因库的信息积累做出贡献。