Zygocotyle lunata inhabits the caecum of birds and mammals from the American continent. This amphistome parasite is easily maintained in the laboratory and serves as a model organism in life-cycle studies, but it has seldom been studied using molecular data. Neither the position of Z. lunata in the superfamily Paramphistomoidea nor the monophyly of the Zygocotylidae has been evaluated with molecular phylogenetic methods. In the present study, adult specimens of Z. lunata obtained experimentally in mice from Brazil were submitted to molecular studies. Partial sequences of nuclear (1261 bp of 28S and 418 bp of 5.8S-ITS-2) and mitochondrial (1410 bp of cytochrome c oxidase 1, cox1) markers were compared with published data. In the most well-resolved phylogeny, based on 28S sequences, Z. lunata clustered in a well-supported clade with Wardius zibethicus, the only other species currently included in the Zygocotylidae, thus confirming the validity of this family. Divergence of 28S sequences between these species was 2.2%, which falls in the range of intergeneric variation (0.9–5.6%) observed in the other two monophyletic groups in the 28S tree, i.e., representatives of Gastrodicidae and Neotropical cladorchiids (Cladorchiidae). Analysis of ITS-2 and two parts of the cox1 gene placed Z. lunata within poorly resolved clades or large polytomies composed of several paramphistomoid families, without clarifying higher-level phylogenetic relationships. The cox1 of a Brazilian isolate of Z. lunata is 99.6% similar to a Canadian isolate, confirming the pan-American distribution of the species. Finally, our phylogenetic reconstructions of Paramphistomoidea revealed a complex scenario in the taxonomic composition of some amphistome families, which highlights a need for further integrative studies that will likely result in rearrangements of traditional morphology-based classifications.

Zygocotyle lunata栖息于美洲大陆鸟类和哺乳动物的盲肠。该amphistome寄生虫很容易在实验室中进行维护，并在生命周期研究中用作模型生物，但很少使用分子数据对其进行研究。既不的位置Z.孢菌在超家族Paramphistomoidea也不Zygocotylidae的单系已经评估与分子系统的方法。在本研究中，通过实验从巴西的小鼠中获得的月牙Z的成年标本已提交分子研究。核的部分序列（28S的1261 bp和5.8S-ITS-2的418 bp）和线粒体的部分序列（细胞色素c氧化酶1的1410 bp ，cox1）将标记与公开数据进行比较。在最完善的解决系统发育，基于28S序列，Z.霉与良好支持的分支聚集Wardius zibethicus，目前列入Zygocotylidae唯一的其他物种，从而证实了这个家庭的有效性。这些物种之间28S序列的差异为2.2％，属于在28S树的其他两个单系组中观察到的属间变异范围（0.9-5.6％），即Gastrodicidae和Neotropical cladorchiids（Cladorchiidae）的代表。ITS-2和两个部分组成的分析COX放置1个基因Z.孢菌在解析度不佳的进化枝或由多个副鞭毛类科组成的大型多形体中，没有阐明更高层次的系统发育关系。巴西Z. lunata分离株的cox 1与加拿大分离株相似，为99.6％，证实了该物种的泛美分布。最后，我们对副鞭毛虫的系统发育重建揭示了一些动物组的分类学组成中的复杂情况，这突出表明需要进行进一步的综合研究，这可能会导致基于传统形态学分类的重新排列。