Chilton N B, Gasser R B, Beveridge I
Department of Veterinary Science, University of Melbourne, Parkville, Victoria, Australia.
Int J Parasitol. 1995 May;25(5):647-51. doi: 10.1016/0020-7519(94)00171-j.
The nucleotide sequence of the second internal transcribed spacer (ITS-2) from ribosomal DNA has been determined for 3 members of the Hypodontus macropi species complex. Sequences were compared from nematodes collected from 3 species of Australian macropodid marsupial, Petrogale persephone, Macropus robustus robustus and Thylogale billardierii. The ITS-2 of each operational taxonomic unit ranged from 287 to 292 bases in length, and had a GC content of 36.6-40.1%. Differences in nucleotide sequence between nematodes from the different host species ranged from 25.0% to 28.3%. The data suggest that H. macropi from P. persephone represents a different species to those in M. r. robustus and T. billardierii. The unique feature of this study is that it represents a comparison of the ribosomal DNA sequences of nematode species which are morphologically indistinguishable but which have been demonstrated to be genetically distinct (i.e. cryptic) species based on electrophoretic data. The results also demonstrate further that morphological characters alone are often not adequate for species recognition. Differences between these 3 species of H. macropi in their recognition sites for restriction endonucleases, indicates that a PCR-RFLP approach could be used, in conjunction with allozyme electrophoresis, to establish how many species are present within the H. macropi complex.
已测定了巨口低齿线虫物种复合体3个成员核糖体DNA的第二内部转录间隔区（ITS-2）的核苷酸序列。对从3种澳大利亚袋鼠科有袋动物，即佩氏岩袋鼠、粗壮袋鼠指名亚种和帚尾袋鼬采集的线虫的序列进行了比较。每个操作分类单元的ITS-2长度在287至292个碱基之间，GC含量为36.6%-40.1%。来自不同宿主物种的线虫之间的核苷酸序列差异在25.0%至28.3%之间。数据表明，来自佩氏岩袋鼠的巨口低齿线虫与粗壮袋鼠指名亚种和帚尾袋鼬体内的巨口低齿线虫代表不同的物种。本研究的独特之处在于，它对形态上无法区分但基于电泳数据已证明在遗传上不同（即隐存）的线虫物种的核糖体DNA序列进行了比较。结果还进一步表明，仅靠形态特征往往不足以进行物种识别。这3种巨口低齿线虫在限制性内切酶识别位点上的差异表明，结合等位酶电泳，PCR-RFLP方法可用于确定巨口低齿线虫复合体中存在多少个物种。
