Laboratório de Protozoologia, Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil.
Laboratório de Protozoologia, Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil.
Environ Pollut. 2021 Jan 1;268(Pt A):115760. doi: 10.1016/j.envpol.2020.115760. Epub 2020 Oct 27.
The aim of our study was to evaluate the water quality of an urban stream in southeastern Brazil by analyzing epibenthic ciliates, and to investigate the existence of phylogenetic signal for saprobity in ciliates. However, before conducting this type of phylogenetic study, it is necessary to evaluate if the saprobic classification used frequently in the northern Hemisphere is suitable for neotropical ecosystems. Sediment samples were collected from five sampling stations: two in rural areas and three in urban areas. During the one-year study, with monthly collections, 39 ciliates species were found, of which 32 are included in the saprobic system. Physical, chemical and biological parameters of water confirm the spatial heterogeneity of the sampling stations, with a clear influence of organic pollution on the composition and structure of ciliates taxocenosis. The saprobic index and the saprobic valence index were used to evaluate the water quality of the sampling stations and demonstrated clear heterogeneity between the stations and high degree of pollution of the urban area. These sampling stations were dominated by ciliates indicators of polysaprobric environments. Since we were able to successfully use the saprobic index in a limnic ecosystem in Brazil, we applied the phylogenetic signal validation as a tool for saprobity prediction of the limnic ciliate species not yet analyzed. A phylogenetic tree containing only 18S-rDNA nominal sequences of freshwater ciliates was estimated and used to explore the existence of the phylogenetic signal, which showed that the sensitivity/tolerance of ciliates to organic pollution reflected evolutionary divergence. The results confirm the existence of phylogenetic signal for the saprobrity in Ciliophora. Also, our results suggest that evolutionary analysis is a potential method to predict lineages of ciliates not yet classified for saprobity.
本研究旨在通过分析附着纤毛虫评估巴西南部城市溪流的水质，并调查纤毛虫在污化指示方面是否存在系统发育信号。然而，在进行此类系统发育研究之前，有必要评估北半球常用的污化分类是否适用于新热带生态系统。从五个采样点采集了沉积物样本：两个在农村，三个在城市地区。在为期一年的研究中，每月进行一次采集，共发现了 39 种纤毛虫，其中 32 种被纳入了污化系统。水的物理、化学和生物参数证实了采样点的空间异质性，有机污染对纤毛虫分类群的组成和结构有明显影响。采用污化指数和污化价指数评估采样点的水质，结果表明各采样点之间存在明显异质性，且城市地区污染程度很高。这些采样点主要由指示多污环境的纤毛虫指示种组成。由于我们成功地在巴西的一个淡水生态系统中使用了污化指数，因此我们将系统发育信号验证应用于尚未分析的淡水纤毛虫物种的污化预测工具。仅包含淡水纤毛虫 18S-rDNA 名义序列的系统发育树被估计并用于探索系统发育信号的存在，结果表明纤毛虫对有机污染的敏感性/耐受性反映了进化分歧。研究结果证实了纤毛虫在污化指示方面存在系统发育信号。此外，我们的结果表明，进化分析可能是预测尚未分类的纤毛虫的污化指示种的潜在方法。
