Zietara Marek S, Lumme Jaakko
Department of Biology, University of Oulu, POB 3000, FI-90014 University of Oulu, Finland.
Syst Parasitol. 2003 May;55(1):39-52. doi: 10.1023/a:1023938415148.
Nucleotide sequences of nuclear ribosomal DNA internal transcribed spacers (ITS) were used to confirm morphological identification of Gyrodactylus species in Fennoscandia. Three pairs of morphologically similar or cryptic species are compared in this study. G. branchicus Malmberg, 1964 and G. rarus Wegener, 1910, hosted by the sticklebacks Gasterosteus aculeatus L. and Pungitius pungitius (L.), respectively, displayed a genetic divergence of 0.9-1.3% along 774 nucleotides of ITS (Jukes & Cantor distance). G. branchicus isolates from the Baltic, White Sea and Scottish North Sea were invariable, but a Belgian North Sea population with a 0.4% divergence in ITS sequence has been collected. The species status of G. branchicus and G. rarus is supported by host-specificity in sympatric habitats and consistent morphological difference in the marginal hook sickles. Among Gyrodactylus on burbot Lota lota (L.) specimens were collected with their 792 bp long ITS sequences differing by 8.5%. This has led to the splitting of G. lotae Gusev, 1953 into two species, G. lotae and G. alexgusevi n. sp. The species are morphologically separable, and a similar range of variation was found in both the anchors and the marginal hooks in other collections and in the original description. Among G. macronychus-like parasites of minnow Phoxinus phoxinus (L.), divergent ITS sequences indicate two cryptic species. By comparison with the type-specimens, one was identified as G. macronychus Malmberg, 1957; the other is here designated as G. jussii n. sp., differing by 21.8% in 950-973 bp long ITS. The consequences of these findings for the species concept and species identification of Gyrodactylus are discussed.
核糖体DNA内转录间隔区（ITS）的核苷酸序列被用于确认芬诺斯坎迪亚地区三代虫属物种的形态学鉴定。本研究比较了三对形态相似或隐秘的物种。分别寄生于棘鱼Gasterosteus aculeatus L.和刺鱼Pungitius pungitius (L.)的1964年描述的分支三代虫G. branchicus Malmberg和1910年描述的稀有三代虫G. rarus Wegener，在ITS的774个核苷酸上显示出0.9 - 1.3%的遗传差异（朱克斯-坎托距离）。来自波罗的海、白海和苏格兰北海的分支三代虫分离株没有差异，但已收集到一个比利时北海种群，其ITS序列有0.4%的差异。分支三代虫和稀有三代虫的物种地位得到了同域栖息地宿主特异性以及边缘钩镰一致形态差异的支持。在江鳕Lota lota (L.)上的三代虫中，收集到的标本其792 bp长的ITS序列差异为8.5%。这导致1953年描述的洛氏三代虫G. lotae Gusev被分为两个物种，即洛氏三代虫G. lotae和新物种亚历克斯古塞夫三代虫G. alexgusevi。这两个物种在形态上是可区分的，并且在其他标本以及原始描述中的锚和边缘钩上也发现了类似的变异范围。在拟鲤Phoxinus phoxinus (L.)的类大爪三代虫中，不同的ITS序列表明存在两个隐秘物种。通过与模式标本比较，一个被鉴定为1957年描述的大爪三代虫G. macronychus Malmberg；另一个在此被指定为新物种朱西三代虫G. jussii，在950 - 973 bp长的ITS上差异为21.8%。讨论了这些发现对三代虫属物种概念和物种鉴定的影响。
