Institute of Parasitology, Slovak Academy of Sciences, Košice, Slovakia,
Parasitol Res. 2013 Oct;112(10):3379-88. doi: 10.1007/s00436-013-3516-y. Epub 2013 Jul 7.
Atractolytocestus tenuicollis (Li, 1964) Xi, Wang, Wu, Gao et Nie, 2009 is a monozoic, non-segmented tapeworm of the order Caryophyllidea, parasitizing exclusively common carp (Cyprinus carpio L.). In the current work, the first molecular data, in particular complete ribosomal internal transcribed spacer 2 (ITS2) and partial mitochondrial cytochrome c oxidase subunit I (cox1) on A. tenuicollis from Niushan Lake, Wuhan, China, are provided. In order to evaluate molecular interrelationships within Atractolytocestus, the data on A. tenuicollis were compared with relevant data on two other congeners, Atractolytocestus huronensis and Atractolytocestus sagittatus. Divergent intragenomic copies (ITS2 paralogues) were detected in the ITS2 ribosomal spacer of A. tenuicollis; the same phenomenon has previously been observed also in two other congeners. ITS2 structure of A. tenuicollis was very similar to that of A. huronensis from Slovakia, USA and UK; overall pairwise sequence identity was 91.7-95.2%. On the other hand, values of sequence identity between A. tenuicollis and A. sagittatus were lower, 69.7-70.9%. Cox1 sequence, analysed in five A. tenuicollis individuals, were 100 % identical and no intraspecific variation was observed. Comparison of A. tenuicollis cox1 with respective sequences of two other Atractolytocestus species showed that the mitochondrial haplotype found in Chinese A. tenuicollis is structurally specific (haplotype 4; Ha4) and differs from all so far determined Atractolytocestus haplotypes (Ha1 and Ha2 for A. huronensis; Ha3 for A. sagittatus). Pairwise sequence identity between A. tenuicollis cox1 haplotype and remaining three haplotypes followed the same pattern as in ITS2. The nucleotide and amino acide (aa) sequence comparison with A. huronensis Ha1 and Ha2 revealed higher sequence identity, 90.3-90.8% (96.9% in aa), while lower values were achieved between A. tenuicollis haplotype and Ha3 of Japanese A. sagittatus-75.2 % (81.9 % in aa). The phylogenetic analyses using cox1, ITS2 and combined cox1 + ITS2 sequences revealed close genetic interrelationship between A. tenuicollis and A. huronensis. Independently of a type of analysis and DNA region used, the topology of obtained trees was always identical; A. tenuicollis formed separate clade with A. huronensis forming a closely related sister group.
本文提供了中国武汉牛山湖的狭长卷棘口吸虫（Atractolytocestus tenuicollis）的第一个分子数据，特别是核糖体内部转录间隔区 2（ITS2）的完整序列和部分线粒体细胞色素 c 氧化酶亚基 I（cox1）的部分序列。为了评估狭长卷棘口吸虫属内的分子系统关系，将狭长卷棘口吸虫的 cox1 数据与另外两个近缘种（A. huronensis 和 A. sagittatus）的相关数据进行了比较。在狭长卷棘口吸虫的 ITS2 核糖体间隔区检测到了不同的基因组内拷贝（ITS2 旁系同源物）；这种现象以前也在另外两个近缘种中观察到过。狭长卷棘口吸虫的 ITS2 结构与来自斯洛伐克、美国和英国的 A. huronensis 非常相似；总的成对序列同一性为 91.7-95.2%。另一方面，狭长卷棘口吸虫与 A. sagittatus 之间的序列同一性值较低，为 69.7-70.9%。对 5 个狭长卷棘口吸虫个体的cox1 序列进行了分析，结果完全相同，没有观察到种内变异。将中国狭长卷棘口吸虫的 cox1 与另外两个狭长卷棘口吸虫种的相应序列进行比较表明，在中国发现的线粒体单倍型在结构上是特异的（单倍型 4；Ha4），与迄今为止确定的所有狭长卷棘口吸虫单倍型（A. huronensis 的 Ha1 和 Ha2；A. sagittatus 的 Ha3）不同。狭长卷棘口吸虫 cox1 单倍型与其余三个单倍型之间的成对序列同一性遵循与 ITS2 相同的模式。与 A. huronensis Ha1 和 Ha2 的核苷酸和氨基酸（aa）序列比较显示，序列同一性较高，为 90.3-90.8%（aa 为 96.9%），而与日本 A. sagittatus 的 Ha3 相比，数值较低，为 75.2%（aa 为 81.9%）。使用 cox1、ITS2 和 cox1+ITS2 联合序列进行的系统发育分析显示，狭长卷棘口吸虫与 A. huronensis 之间存在密切的遗传关系。无论使用哪种分析方法和 DNA 区域，得到的树的拓扑结构始终相同；狭长卷棘口吸虫与 A. huronensis 形成单独的分支，形成密切相关的姐妹群。
