The cosmopolitan genus Euplotes Ehrenberg, 1830 comprises a highly distinguishable group of ciliates. However, details of the cell surface, the ciliature, and molecular data are still scarce for some species. We studied Euplotes octocarinatus Carter, 1972 from two Mexican freshwater bodies, providing data on its morphology, SSU rRNA gene sequence, and phylogeny. In addition, we obtained all data of previous records to show its geographic distribution and biogeographical pattern. The current populations showed some differences as compared with the original description and we provide an improved diagnosis. Morphologically, the species is very similar to Euplotes patella and E. daidaleos but differs by invariably having eight dorsolateral kineties (vs. nine in Euplotes patella and E. daidaleos), and lacking endosymbiotic green algae (vs. present in E. daidaleos). Phylogenetically, the Mexican population of E. octocarinatus nested with four isolates of the species lacking morphological characterization. The Euplotes octocarinatus described herein grouped into a fully-supported clade, which includes E. patella, E. amieti, E. daidaleos, E. eurystomus, E. woodruffi and E. aediculatus. Biogeographically, E. octocarinatus seems to have a wide distribution.

国际化的Euplotes Ehrenberg属，1830年，由一群纤毛虫组成。但是，对于某些物种，细胞表面，纤毛和分子数据的细节仍然很少。我们从两个墨西哥淡水水体研究了Euplotes octocarinatus Carter，1972年，提供了有关其形态，SSU rRNA基因序列和系统发育的数据。此外，我们获得了先前记录的所有数据，以显示其地理分布和生物地理模式。当前的人群与原始描述相比显示出一些差异，我们提供了改进的诊断。在形态上，该物种与Eu骨Euplotes pat骨和E.非常相似。Daidaleos但通过具有总是（在与九八背外侧动力学的研究不同游仆虫髌骨和ë。daidaleos），并且缺乏内共生绿藻（存在于与ë。daidaleos）。在系统发育上，墨西哥的E种群。octocarinatus嵌套有四个缺乏形态学特征的物种分离物。的游仆虫本文描述分组到完全支持的进化枝，其包括ë。髌骨，ê。amieti，ê。daidaleos，è。eurystomus，E。woodruffi和Ë。刺。。在生物地理学上，E。octocarinatus似乎分布广泛。