Senckenberg Research Institute, German Center for Marine Biodiversity Research (DZMB), Südstrand 44, 26382, Wilhelmshaven, Germany.
Mol Ecol Resour. 2013 Sep;13(5):862-76. doi: 10.1111/1755-0998.12139. Epub 2013 Jul 13.
Calanoid copepods play an important role in the pelagic ecosystem making them subject to various taxonomic and ecological studies, as well as indicators for detecting changes in the marine habitat. For all these investigations, valid identification, mainly of sibling and cryptic species as well as early life history stages, represents a central issue. In this study, we compare species identification methods for pelagic calanoid copepod species from the North Sea and adjacent regions in a total of 333 specimens. Morphologically identified specimens were analysed on the basis of nucleotide sequences (i.e. partial mitochondrial cytochrome c oxidase subunit I (COI) and complete 18S rDNA) and on proteome fingerprints using the technology of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). On all three molecular approaches, all specimens were classified to species level indicated by low intraspecific and high interspecific variability. Sequence divergences in both markers revealed a second Pseudocalanus species for the southern North Sea identified as Pseudocalanus moultoni by COI sequence comparisons to GenBank. Proteome fingerprints were valid for species clusters irrespective of high intraspecific variability, including significant differences between early developmental stages and adults. There was no effect of sampling region or time; thus, trophic effect, when analysing the whole organisms, was observed in species-specific protein mass spectra, underlining the power of this tool in the application on metazoan species identification. Because of less sample preparation steps, we recommend proteomic fingerprinting using the MALDI-TOF MS as an alternative or supplementary approach for rapid, cost-effective species identification.
钙质桡足类在浮游生态系统中扮演着重要的角色，这使得它们成为各种分类学和生态学研究的对象，同时也是检测海洋生境变化的指标。对于所有这些研究，有效的鉴定，主要是针对姐妹种和隐种以及早期生活史阶段，是一个核心问题。在这项研究中，我们比较了来自北海和邻近地区的 333 个浮游钙质桡足类标本的物种鉴定方法。形态学鉴定的标本基于核苷酸序列（即部分线粒体细胞色素 c 氧化酶亚基 I（COI）和完整的 18S rDNA）和使用基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）技术的蛋白质组指纹图谱进行分析。在所有三种分子方法中，所有标本都被分类到种水平，这表明种内变异性低，种间变异性高。两种标记物的序列差异揭示了南北海的第二个拟哲水蚤物种，通过与 GenBank 中的 COI 序列比较，鉴定为拟哲水蚤 moultoni。蛋白质组指纹图谱对于物种聚类是有效的，无论种内变异性高低如何，包括早期发育阶段和成虫之间的显著差异。采样区域或时间没有影响；因此，在分析整个生物体时，在种特异性蛋白质质谱中观察到了营养效应，这强调了这种工具在后生动物物种鉴定中的应用能力。由于样品制备步骤较少，我们建议使用 MALDI-TOF MS 进行蛋白质组指纹图谱分析，作为快速、经济有效的物种鉴定的替代或补充方法。
