Xu Xiaojing, Lundholm Nina, Li Yang
Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, College of Life Science, South China Normal University, West 55 of Zhongshan Avenue, Guangzhou, 510631, P.R. China.
Natural History Museum of Denmark, University of Copenhagen, Øster Farimagsgade 5, 1307, Copenhagen K, Denmark.
J Phycol. 2020 Jun;56(3):784-797. doi: 10.1111/jpy.12982. Epub 2020 Mar 23.
Chaetoceros debilis is considered one of the most abundant and widespread diatoms in the coastal marine phytoplankton, and is often used in research studies ranging from ecophysiology and molecular biology to oceanography and aquaculture. To clarify the species delineation of C. debilis and explore the diversity among C. debilis sensu lato taxa, monoclonal strains were established from different geographical regions, including the Danish coast, close to the type locality of C. debilis, the Denmark Strait (between Iceland and Greenland) as well as the Taiwan Strait, East China Sea and Daya Bay, South China Sea. Vegetative cells and resting spores were examined using light and electron microscopy. The hypervariable D1-D3 region of the nuclear large subunit ribosomal gene and the small subunit ribosomal gene were sequenced to address phylogenetic relationships. In both SSU and LSU trees, the C. debilis sensu lato strains clustered in four distinct clades. Culture material from the type locality was, along with molecular data, used to delineate and emend the description of C. debilis. Based on molecular data and detailed morphological features, one of the clades originating from Chinese waters was described as C. galeatus sp. nov., characterized by curved and helical chains, elliptical valves, and smooth and helmet-shaped primary valves of the resting spores. The remaining two clades, which also represent two novel taxa, C. cf. debilis-1 and C. cf. debilis-2, were not formally described as new species due to the insufficient information on their morphology.
柔弱角毛藻被认为是沿海水域浮游植物中数量最多、分布最广的硅藻之一，常用于从生态生理学、分子生物学到海洋学和水产养殖等研究领域。为了厘清柔弱角毛藻的物种界定，并探索广义柔弱角毛藻分类群之间的多样性，我们从不同地理区域建立了单克隆菌株，包括靠近柔弱角毛藻模式产地的丹麦海岸、丹麦海峡（冰岛和格陵兰岛之间）以及台湾海峡、中国东海和中国南海大亚湾。利用光学显微镜和电子显微镜对营养细胞和休眠孢子进行了检查。对核糖体大亚基基因和小亚基基因的高变D1-D3区域进行测序，以确定系统发育关系。在小亚基和大亚基树中，广义柔弱角毛藻菌株聚为四个不同的分支。来自模式产地的培养材料与分子数据一起，用于界定和修订柔弱角毛藻的描述。基于分子数据和详细的形态特征，源自中国水域的一个分支被描述为新物种盔形角毛藻，其特征为弯曲和螺旋状的链、椭圆形的瓣膜以及休眠孢子光滑且呈头盔状的初级瓣膜。由于另外两个分支的形态信息不足，它们虽然也代表两个新分类群，即柔弱角毛藻近似种-1和柔弱角毛藻近似种-2，但未被正式描述为新物种。
