Thompson Christine M, North Elizabeth W, Kennedy Victor S, White Sheri N
Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, MD, 21613, USA,
Anal Bioanal Chem. 2015 May;407(13):3591-604. doi: 10.1007/s00216-015-8575-8. Epub 2015 Mar 11.
Because bivalve larvae are difficult to identify using morphology alone, the use of Raman spectra to distinguish species could aid classification of larvae collected from the field. Raman spectra from shells of bivalve larvae exhibit bands that correspond to polyene pigments. This study determined if the types of shell pigments observed in different species could be unique enough to differentiate larvae using chemotaxonomic methods and cluster analysis. We collected Raman spectra at three wavelengths from 25 samples of bivalve larvae representing 16 species and four taxonomic orders. Grouping spectra within general categories based on order/family relationships successfully classified larvae with cross-validation accuracies ≥92% for at least one wavelength or for all wavelengths combined. Classifications to species were more difficult, but cross-validation accuracies above 86% were observed for 7 out of 14 species when tested using species groups within orders/families at 785 nm. The accuracy of the approach likely depends on the composition of species in a sample and the species of interest. For example, high classification accuracies (85-98%) for distinguishing spectra from Crassostrea virginica larvae were achieved with a set of bivalve larvae occurring in the Choptank River in the Chesapeake Bay, USA, whereas as lower accuracies (70-92%) were found for a set of C. virginica larvae endemic to the Northeast, USA. In certain systems, use of Raman spectra appears to be a promising method for assessing the presence of certain bivalves in field samples and for validating high-throughput image analysis systems for larval bivalve studies.
由于仅通过形态学很难识别双壳类幼虫，利用拉曼光谱来区分物种有助于对从野外采集的幼虫进行分类。双壳类幼虫贝壳的拉曼光谱显示出与多烯色素相对应的谱带。本研究确定了不同物种中观察到的贝壳色素类型是否独特到足以使用化学分类方法和聚类分析来区分幼虫。我们从代表16个物种和4个分类目的25个双壳类幼虫样本中，在三个波长下收集了拉曼光谱。基于目/科关系在一般类别内对光谱进行分组，成功地对幼虫进行了分类，至少在一个波长或所有波长组合下，交叉验证准确率≥92%。按物种分类更困难，但在785 nm处使用目/科内的物种组进行测试时，14个物种中有7个的交叉验证准确率高于86%。该方法的准确性可能取决于样本中物种的组成以及感兴趣的物种。例如，在美国切萨皮克湾乔普坦克河中出现的一组双壳类幼虫中，区分弗吉尼亚牡蛎幼虫光谱的分类准确率很高（85-98%），而在美国东北部特有的一组弗吉尼亚牡蛎幼虫中，准确率较低（70-92%）。在某些系统中，使用拉曼光谱似乎是一种很有前景的方法，可用于评估野外样本中某些双壳类的存在，并用于验证双壳类幼虫研究的高通量图像分析系统。
