广东沿海洛氏角毛藻复合群物种多样性的探究

PRELIMINARY STUDY ON THE SPECIES DIVERSITY OF CHAETOCEROS LORENZIANUS COMPLEX FROM GUANGDONG COASTAL WATERS

  • 摘要: 为了澄清洛氏角毛藻复合群的物种多样性, 并明确洛氏角毛藻和并基角毛藻的种间界限, 文章以广东沿海为例, 建立了洛氏角毛藻复合群的22个单克隆培养株系, 利用光学显微镜和电子显微镜技术, 开展了基于生活史的连续形态学观察; 结合基于核糖体大亚基编码基因D1-D3区序列的分子系统学分析。结果表明: 文章支持近年研究的观点, 认为“角毛基部并行融合”不是稳定特征, 不宜继续作为并基角毛藻的标志特征; 发现洛氏角毛藻形态相似藻株聚类在2个分支上, 确认了洛氏角毛藻确实存在隐藏的物种多样性。其中一类与目前认知的洛氏角毛藻最为接近, 而另一类在角毛孔纹、休眠孢子上存在明显区别。经过对洛氏角毛藻历史文献的对比研究, 发现洛氏角毛藻的物种界定存在混乱和模糊的情况, 如休眠孢子形态, 及其初生壳面是否具有二叉状分布结构等, 均存在相互矛盾或不一致的历史报道。

     

    Abstract: In order to understand the diversity of Chaetoceros lorenzianus complex and divide C. decipiens and C. lorenzianus clearly, Guangdong coast was chosen as a case studied area and a total of 22 monoclonal strains within C. lorenzianus complex were established in this study. Using optical and electron microscopy, their morphology was observed through life cycle, including vegetative cells and resting spores. Hypervariable D1-D3 region of nuclear ribosomal large subunit encode gene for each strain was amplified and their molecular systematics was studied. Following conclusions were made based on the combination of morphology and molecular data. The results showed that the fusing setae base was not a steady feature and could not be considered as an exclusive characteristic for C. decipiens, which supporting the opinion from Chen et al. (2017). The strains with similar morphology with C. lorenzianus located into two clades, and it indicated the presence of unexplored species in C. lorenzianus complex. The strains in one clade shared most similar morphology with present-known C. lorenzianus, and those in another clade were distinct in the morphologies of setae poroid and resting spore. When compared wtih C. lorenzianus descriptions in previous studies, confusion and disorder for C. lorenzianus delineation were found. For example, there were contradictory and competing descriptions on the shape of resting spore and the presence of dichotomous branches on the primary valve. In future studies, the re-examination on type C. lorenzianus materials, including the vegetative cells and resting spores, is proposed to be conducted preferentially, and then the true diversity might be achieved.

     

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