圆筒吻鮈食性与消化道微生物群落结构对三峡水库运行后环境变化的响应

The feeding habits and the gut microbial community are closely related to the survival of fish, which are easily effected by the environmental factors. After the operation of Three Gorges Reservoir (TGR), the habitat and food organisms have been changed significantly for the endemic fish species in the upper reaches of the Yangtze River. The index of relative importance of Rhinogobio cylindricus is the highest among the endemic fish species in TGR, and its responses to the environmental changes after the operation of TGR need a further study. Therefore, this project will focus on the responses of feeding habits and the gut microbial community of Rhinogobio cylindricus to the environmental changes by the operation of TGR. By using metagenomics analysis, stable isotope analysis, traditional identification methods, the characteristics of feeding habits and the gut microbial community structure will be studied as well as their differences in different habitats and life stage. And the feeding habits and the gut microbial community structure of Rhinogobio cylindricus were analyzed with relation to the environmental factors, food organisms and aquatic microbial community. The relationships will also be analyzed between the succession of gut microbial community and changes of feeding habits. Then, the most important factors influencing the feeding habits and the gut microbial community succession will be analyzed. Based on the results above, the responses to environmental changes will be revealed for the feeding habits and the gut microbial community structure of Rhinogobio cylindricus. The results of the project are important for us to further understand the effects of TGR operation on endemic fish and the functional value of habitat maintenance of species diversity in TGR and its upper reaches. It can also provide scientific basis for the protection of endemic fish in the upper reaches of the Yangtze River.

鱼类食性、消化道微生物均与鱼类生存紧密相关，且易受外界环境影响。三峡水库运行后，随着库区的生境、饵料生物等生存环境改变，圆筒吻鮈成为特有鱼类中相对优势度最高的种类，其对环境变化的响应有待进一步研究。为此，本项目以圆筒吻鮈为对象，利用宏基因组分析、稳定同位素分析、传统鉴定等多种方法，研究圆筒吻鮈食性特征、消化道微生物群落结构及其在不同生境、生活史阶段的差异与变动规律；通过分析圆筒吻鮈食性与生境条件、饵料生物群落等环境因子的关系，以及消化道微生物群落与生境条件、水体微生物、食性转变的关系，辨识影响圆筒吻鮈食性特征的主要因素、消化道微生物群落如何演替与构建，从而揭示圆筒吻鮈食性特征、消化道微生物群落对工程运行后环境条件变化的响应。项目成果对于进一步认知工程运行对特有鱼类的影响、三峡库区及以上江段栖息地维持物种多样性的功能价值具有重要意义，也可为长江上游特有鱼类保护提供科学基础。

鱼类食性、消化道微生物与鱼类生存紧密相关，且易受外界环境影响。本项目以特有鱼类圆筒吻鮈为对象，研究了圆筒吻鮈食性与消化道微生物群落结构特征及其在三峡库尾及其上游不同江段、成幼鱼不同阶段的变化规律，分析了影响其食性特征、消化道微生物群落的主要因素，进而探讨了其食性、消化道微生物群落对三峡水库运行后环境条件的响应及其适应机制。主要结果表明：（1）综合胃肠内含物分析、稳定同位素分析结果，圆筒吻鮈主要摄食浮游生物、着生藻类、虾类、淡水壳菜、水生昆虫等。（2）稳定同位素分析结果表明：圆筒吻鮈主要食物组成在夏季、秋季呈现差异，着生藻类在夏季圆筒吻鮈食物中平均贡献率最高，但在秋季则明显下降，而浮游生物及虾类在秋季较夏季明显上升。（3）圆筒吻鮈在不同江段间的主要食物组成存在差异；合江江段圆筒吻鮈的平均生态位最宽，表明合江江段的食物可获得性最高。（4）夏季圆筒吻鮈主要食物组成在成幼鱼阶段间无显著性差异，但在秋季存在差异，引起差异的食物主要为浮游生物。夏季圆筒吻鮈的平均生态位宽度在成幼鱼阶段间无明显差异，但秋季圆筒吻鮈成鱼平均生态位宽度显著高于幼鱼。（5）影响圆筒吻鮈食物组成的最关键因子是采样江段，而影响其营养级的最关键因子是个体体重。（6）圆筒吻鮈肠道微生物群落在不同样点间、季节间有显著差异的OTUs，但是这些差异并没有呈现出与三峡工程运行明显的相关性。（7）秋季木洞江段圆筒吻鮈肠道微生物群落在幼鱼、成鱼间总体没有明显差异，其优势门中仅有酸杆菌门和迷踪菌门的相对丰度在幼鱼和成鱼之间存在显著差异。（8）采样地点、采样时间、性腺发育期、肠饱和度、性别等因素显著影响夏季圆筒吻鮈肠道菌群组成。（9）圆筒吻鮈肠道可能对进入其中的细菌有强选择性，从而在很大程度上降低了不同生境水体菌群变化对其造成的影响。项目成果对进一步认知鱼类对环境变化的响应及适应机制、三峡库区及以上江段鱼类保护等具有重要意义。