Platta Christopher S, Choudhury Anindo
Division of Natural Sciences, St. Norbert College, DePere, Wisconsin 54115, USA.
J Parasitol. 2006 Apr;92(2):411-3. doi: 10.1645/GE-3521RN.1.
Paracreptotrematina limi Amin and Myer, 1982 (Trematoda), an intestinal fluke specific to the mudminnow, Umbra limi, is conventionally classified within the papillose Allocreadiidae. Its unusual morphology (lack of identifiable vitellaria, large fully embryonated terminal eggs), assumptions of homology of its 2 atypical muscular oral 'papillae' (lobes) with those of the Bunoderinae, and its unknown life cycle make this classification tenuous. Previous phylogenetic analyses of the papillose allocreadiids, based on morphology, placed P. limi as a basal papillose allocreadiid. We tested this hypothesis with a phylogenetic analysis by using partial sequences of the 28S ribosomal RNA gene and the cytochrome c oxidase subunit I gene from several plagiorchiiform taxa, including reportedly related allocreadiids as well as selected species of Plagiorchiidae, Haematoloechidae, and Macroderoididae. Results of phylogenetic analyses of the 28S rRNA gene fragments by using parsimony criteria support the classification of P. limi as an allocreadiid and place it as a sister taxon to a clade with Allocreadium lobatum Wallin, 1909, Bunodera luciopercae (Müller, 1876) and Crepidostomum cooperi Hopkins, 1931, with Polylekithum ictaluri (Pearse, 1924) basal to all of them. Analysis of the cytochrome c oxidase subunit I gene sequence data from fewer taxa supports the placement of P. limi relative to 3 (A. lobatum, C. cooperi, and P. ictaluri) of the 4 allocreadiid taxa. These results also suggest that the previous conception of the papillose allocreadiids as a monophyletic assemblage that includes P. limi may require a reappraisal.
1982年，阿米恩和迈尔发现的泥塘鳢肠道吸虫（吸虫纲），是泥塘鳢特有的一种肠道吸虫，传统上被归类于具乳头状突起的异肉科。其形态异常（缺乏可识别的卵黄腺，大型完全胚胎化的终端卵），其两个非典型肌肉性口腔“乳头”（叶）与布诺德亚科的乳头假定存在同源性，且其生命周期未知，使得这种分类存在疑问。先前基于形态学对具乳头状突起的异肉科进行的系统发育分析，将泥塘鳢肠道吸虫置于具乳头状突起的异肉科基部。我们通过系统发育分析对这一假设进行了检验，使用了来自几个斜睾目分类群的28S核糖体RNA基因和细胞色素c氧化酶亚基I基因的部分序列，包括据报道相关的异肉科以及斜睾科、血居科和巨口科的选定物种。使用简约标准对28S rRNA基因片段进行系统发育分析的结果支持将泥塘鳢肠道吸虫归类为异肉科，并将其置于与1909年沃林发现的叶状异肉吸虫、1876年米勒发现的鲈布诺德吸虫和1931年霍普金斯发现的库珀隐殖吸虫的一个分支的姐妹分类单元中，而1924年皮尔斯发现的鲶多卵吸虫位于所有这些分类单元的基部。对较少分类群的细胞色素c氧化酶亚基I基因序列数据的分析支持了泥塘鳢肠道吸虫相对于4个异肉科分类单元中的3个（叶状异肉吸虫、库珀隐殖吸虫和鲶多卵吸虫）的位置。这些结果还表明，先前将具乳头状突起的异肉科视为包括泥塘鳢肠道吸虫的单系类群的概念可能需要重新评估。
