Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
Universidade Federal do Mato Grosso do Sul (UFMS), Campo Grande, Brazil.
PLoS One. 2018 Jul 6;13(7):e0200390. doi: 10.1371/journal.pone.0200390. eCollection 2018.
The genus Cooperia includes important parasites of ruminants and currently contains 34 accepted species. However, even for those species infecting livestock, there is a considerable lack of molecular information and many species are only identifiable using subtle morphological traits. The present study aimed to provide molecular data to allow diagnosis of Cooperia species infecting cattle. Partial sequences of two mitochondrial (cytochrome oxidase 2, 12S rRNA gene) and two nuclear genes (isotype 1 β tubulin gene including two introns, internal transcribed spacers (ITS) were obtained from morphologically identified specimens of Cooperia pectinata, Cooperia punctata and Cooperia spatulata as well as from larvae of pure Cooperia oncophora and C. punctata laboratory isolates. Pairwise identity of ITS-2 sequences was very high and it was the only region able to identify a specimen as Cooperia sp. However, the ITS-2 was unreliable for diagnosis at the species level. All other marker sequences could not unequivocally be allocated to the genus Cooperia but allowed clear species identification with the exception of the pair C. punctata/C. spatulata for which no significant differences were found for any marker sequence. Maximum-likelihood phylogenetic analyses of individual genes as well as a multi-locus analysis covering all four sequences confirmed that specimen identified as C. spatulata were randomly distributed throughout the C. punctata cluster and formed no group of their own. In contrast, the other Cooperia species formed clearly separated and statistically supported clusters. These data indicate that C. spatulata is most likely only a morphotype of C. punctata and the name should be considered a synonym. Combinations of nuclear and mitochondrial markers should be used to identify morphotypes or cryptic species to benefit from excellent barcoding properties of the latter but allowing proper phylogenetic analyses and controlling for lineage sorting that might occur for mitochondrial genotypes within a species.
该属包括反刍动物的重要寄生虫，目前包含 34 个公认的物种。然而，即使是那些感染家畜的物种，也缺乏相当多的分子信息，许多物种只能通过微妙的形态特征来识别。本研究旨在提供分子数据，以允许诊断感染牛的 Cooperia 物种。从形态学上鉴定的旋毛虫属 pectinata、旋毛虫属 punctata 和旋毛虫属 spatulata 以及纯旋毛虫属 oncophora 和 C. punctata 实验室分离物的幼虫中获得了两个线粒体（细胞色素氧化酶 2、12S rRNA 基因）和两个核基因（同工型 1β微管蛋白基因，包括两个内含子、内部转录间隔区（ITS）的部分序列。ITS-2 序列的成对同一性非常高，它是唯一能够鉴定标本为 Cooperia sp. 的区域。然而，ITS-2 对于种水平的诊断不可靠。所有其他标记序列不能明确分配到 Cooperia 属，但允许明确的物种鉴定，除了 C. punctata/C. spatulata 对，对于任何标记序列都没有发现显著差异。个体基因的最大似然系统发育分析以及包含所有四个序列的多基因座分析均证实，鉴定为 C. spatulata 的标本随机分布在 C. punctata 聚类中，并未形成自己的群体。相比之下，其他 Cooperia 物种形成了明显分离且统计学上支持的聚类。这些数据表明，C. spatulata 很可能只是 C. punctata 的一种形态型，该名称应被视为同义词。应使用核和线粒体标记组合来鉴定形态型或隐种，以利用后者的出色条形码特性，但要进行适当的系统发育分析，并控制物种内线粒体基因型可能发生的谱系排序。
