Evaluation of combined morphological and molecular techniques for marine nematode (Terschellingia spp.) identification
Evaluation of combined morphological and molecular techniques for marine nematode (Terschellingia spp.) identification
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DOI：
10.1007/s00227-008-0945-8
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发表时间：
2008-05-01
期刊：
影响因子：
2.4
通讯作者：
Smerdon, G. R.
中科院分区：
文献类型：
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作者：
Bhadury, P.;Austen, M. C.;Smerdon, G. R.
海洋线虫在许多生态系统中发挥着重要作用，包括许多明显的世界性类群，尽管在其生命周期中没有明显的扩散阶段，但它们表现出广泛的生物地理范围。在这项研究中，将海洋线虫鉴定的标准分类方法与形态测量数据的多变量统计分析相结合，与分子技术进行了比较。采用基于小亚基核糖体 RNA (18S rRNA) 扩增和测序的分子方法，对一系列地点（东大西洋和西大西洋、巴林、马来西亚）和栖息地（河口、潮间带、潮下带）的海洋线虫 Terschellingia longicaudata 样本进行了调查，这些样本已通过其形态特征进行了鉴定。研究表明，大多数形态学定义的 T. longicaudata 标本共享一个 18S rRNA 序列，并且显然属于从不列颠群岛到马来西亚分布的单一分类单元。此外，18S rRNA 分析还揭示了两个额外的序列。其中一个序列在不列颠群岛和墨西哥均发现，另一个仅在英国水域记录。在巴林收集并从形态学上鉴定为 T. longicaudata 的个体具有两个高度分歧的 18S rRNA 序列。用单独的形态学和形态测量方法来鉴定来自福尔马林保存的同一地点的标本并不支持先前通过分子分析揭示的多种基因型的证据。目前基于使用光学显微镜检测到的形态特征的分类法可能无法区分可能的物种复合体。由于形态上神秘的物种复合体的存在，海洋线虫的生物多样性常常被低估。 DNA 条形码等高通量技术将有助于物种鉴定，但可能需要对多个核和线粒体分子标记进行彻底分析。
Marine nematodes, which play an important role in many ecosystems, include a number of apparently cosmopolitan taxa that exhibit broad biogeographic ranges even though there is no obvious dispersal phase in their lifecycle. In this study, standard taxonomic approaches to marine nematode identification in conjunction with multivariate statistical analysis of morphometric data were compared with molecular techniques. Specimens of the marine nematode Terschellingia longicaudata that had been identified by their morphological features were investigated from a range of localities (East and West Atlantic, Bahrain, Malaysia) and habitats (estuarine, intertidal, subtidal) using molecular approaches based on the amplification and sequencing of the small subunit ribosomal RNA (18S rRNA). The study revealed that the majority of the morphologically defined T. longicaudata specimens share a single 18S rRNA sequence and apparently belong to a single taxon distributed from the British Isles to Malaysia. In addition, 18S rRNA analysis also revealed two additional sequences. One of these sequences was found in both the British Isles and Mexico, the other was recorded only from British waters. Individuals collected in Bahrain and identified from their morphology as T. longicaudata had two highly divergent 18S rRNA sequences. Separate morphological and morphometric approaches to identification of specimens from the same sites that had been formalin-preserved did not support evidence of multiple genotypes revealed previously by molecular analysis. Current taxonomy based on morphological characters detected using light-microscopy may be unable to discriminate possible species complexes. Biodiversity of marine nematodes may often be underestimated due to the presence of morphologically cryptic species complexes. High-throughput techniques such as DNA barcoding would aid in species identification but may require thorough analysis of multiple nuclear and mitochondrial molecular markers.