Departament of Parasitology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Department of Biology, University of Puerto Rico at Mayagüez, Puerto Rico.
Infect Genet Evol. 2018 Sep;63:95-103. doi: 10.1016/j.meegid.2018.05.010. Epub 2018 May 18.
Species of the genus Posthodiplostomum are intestinal parasites of piscivorous birds with worldwide distribution. Recent molecular surveys have focused on developmental stages from vertebrate hosts, with few sequences from larvae found in molluscs. Moreover, most published molecular data are from collections in North America, Europe and Asia, and there are no data for South American species. In the present study, cercariae found in the freshwater limpet Gundlachia ticaga from Brazil were used for morphological, experimental and molecular studies. The longifurcate cercariae, Neascus-type metacercariae obtained in experimentally infected guppies (Poecilia reticulata), and an adult parasite recovered from a mouse were morphologically identified as Posthodiplostomum nanum. Sequences of DNA from internal transcribed spacer (ITS) rDNA and cytochrome c oxidase 1 (cox1) from the cercariae and metacercariae were compared with published data, yielding no matches (ITS divergence ≥ 5.5%, cox1 ≥ 13.9%). Phylogenetic analyses of the ITS sequences suggest paraphyly within the genus Posthodiplostomum, or misidentifications of parasites in molecular studies. For example, ITS sequences of Mesoophorodiplostomum pricei and Posthodiplostomum centrarchi or the unnamed species Posthodiplostomum sp. 8 diverge by only 1.1-1.2% and 0.6%, respectively, and all three species fall within a well-supported clade, suggesting that these isolates are congeneric. The phylogenetic tree obtained for cox1 sequences, although not well resolved, reveals that the type species of the genus, Posthodiplostomum cuticola, does not group with any species previously identified as Posthodiplostomum. Overall, the analyses of molecular data here obtained for P. nanum compared with sequences of related species suggest that a review of this group is necessary. Such studies may result in a split of the genus Posthodiplostomum and the transference of some species currently assigned in this genus to other already described genera.
后殖盘属（Posthodiplostomum）的物种是分布于全球的肉食性鸟类的肠道寄生虫。最近的分子调查主要集中在脊椎动物宿主的发育阶段，在软体动物中发现的幼虫序列很少。此外，大多数已发表的分子数据来自北美、欧洲和亚洲的收藏，而南美物种则没有数据。在本研究中，使用来自巴西淡水石鳖（Gundlachia ticaga）的尾蚴进行形态学、实验和分子研究。在实验感染的孔雀鱼（Poecilia reticulata）中获得的长分叉尾蚴、Neascus 型的囊蚴和从老鼠体内回收的成虫寄生虫被形态学鉴定为 Posthodiplostomum nanum。从尾蚴和囊蚴的内部转录间隔区（ITS）rDNA 和细胞色素 c 氧化酶 1（cox1）获得的 DNA 序列与已发表的数据进行了比较，没有匹配（ITS 差异≥5.5%，cox1≥13.9%）。ITS 序列的系统发育分析表明，后殖盘属内存在并系关系，或者在分子研究中寄生虫的鉴定有误。例如，Mesoophorodiplostomum pricei 和 Posthodiplostomum centrarchi 的 ITS 序列或未命名的 Posthodiplostomum sp. 8 仅相差 1.1-1.2%和 0.6%，这三个物种都属于一个支持度很高的分支，表明这些分离株是同属的。cox1 序列获得的系统发育树虽然分辨率不高，但表明该属的模式种 Posthodiplostomum cuticola 并不与以前鉴定为 Posthodiplostomum 的任何物种聚在一起。总的来说，与相关物种的分子数据相比，对 P. nanum 的分析表明有必要对该组进行审查。此类研究可能导致后殖盘属的分裂，并将一些目前归入该属的物种转移到其他已描述的属中。
