Due to extensive morphological plasticity, the taxonomy of Cladophora species remains unclear. As one of the widely distributed species, C. gracilis was reported to hold many varieties, which make it difficult to identify the species. This study explored the morphology diversity of nine C. gracilis samples collected along the coast of western Yellow Sea. Some samples showed extremely varied characteristics, by which one cannot classify them correctly. Hence, 18S rDNA and nuclear ribosomal DNA internal transcribed spacer regions (ITS) sequences were employed to delimit species. For 18S rDNA, sequence similarity ranged from 99.6% to 100%. For ITS region, the similarity ranged from 98.7% to 100%. Molecular data strongly suggested that the morphologically heterogeneous samples were actually the same species. Characteristics comparison of the samples revealed that the taxonomy criteria including branching pattern and density, thallus color, height and texture varied widely, influenced by environmental conditions and age of alga. Besides, cell dimensions, as the relatively stable criterion, also exhibited intraspecific variance. Successful application of 18S rDNA and ITS sequences indicated that molecular method can be a powerful assistant as DNA barcodes to traditional morphology taxonomy.

由于广泛的形态可塑性，枝形刺果属的分类学仍然不清楚。据报道，作为一种广泛分布的物种，纤毛梭菌拥有许多变种，这使得很难鉴定该物种。这项研究探索了9个纤毛梭菌的形态多样性沿黄海西部沿海收集的样本。一些样本显示出千差万别的特征，因此无法正确分类。因此，18S rDNA和核糖体DNA内部转录间隔区（ITS）序列被用来界定物种。对于18S rDNA，序列相似性在99.6％至100％之间。对于ITS地区，相似度范围为98.7％至100％。分子数据强烈表明，形态上异质的样品实际上是同一物种。样品的特征比较表明，受环境条件和藻类年龄的影响，分类标准包括分支模式和密度，藻类颜色，高度和质地变化很大。此外，作为相对稳定标准的细胞尺寸也表现出种内差异。