Gaonkar Chetan C, Kooistra Wiebe H C F, Lange Carina B, Montresor Marina, Sarno Diana
Stazione Zoologica Anton Dohrn, Villa Comunale, 80121, Naples, Italy.
Department of Oceanography, Centers COPAS Sur-Austral and FONDAP-IDEAL, University of Concepción, Concepción, Chile.
J Phycol. 2017 Aug;53(4):889-907. doi: 10.1111/jpy.12554. Epub 2017 Jul 5.
The diatom genus Chaetoceros is one of the most abundant and diverse phytoplankton in marine and brackish waters worldwide. Within this genus, Chaetoceros socialis has been cited as one of the most common species. However, recent studies from different geographic areas have shown the presence of pseudo-cryptic diversity within the C. socialis complex. Members of this complex are characterized by curved chains (primary colonies) aggregating into globular clusters, where one of the four setae of each cell curves toward the center of the cluster and the other three orient outwards. New light and electron microscopy observations as well as molecular data on marine planktonic diatoms from the coastal waters off Chile revealed the presence of two new species, Chaetoceros sporotruncatus sp. nov. and C. dichatoensis. sp. nov. belonging to the C. socialis complex. The two new species are similar to other members of the complex (i.e., C. socialis and C. gelidus) in the primary and secondary structure of the colony, the orientation pattern of the setae, and the valve ultrastructure. The only morphological characters that can be used to differentiate the species of this complex are aspects related to resting spore morphology. The two newly described species are closely related to each other and form a sister clade to C. gelidus in molecular phylogenies. We also provide a phylogenetic status along with the morphological characterization of C. radicans and C. cintus, which are genetically related to the C. socialis complex.
硅藻属角毛藻是全球海洋和咸淡水中数量最多、种类最丰富的浮游植物之一。在这个属中，群居角毛藻被认为是最常见的物种之一然而，最近来自不同地理区域的研究表明，群居角毛藻复合体中存在假隐存多样性。该复合体的成员特征是弯曲的链（初级群体）聚集成球状簇，每个细胞的四根刚毛中有一根向簇中心弯曲，另外三根向外伸展。对智利沿海水域海洋浮游硅藻的新光学和电子显微镜观察以及分子数据显示，存在两个新物种，即截断角毛藻新种和叉状角毛藻新种，它们属于群居角毛藻复合体。这两个新物种在群体的一级和二级结构、刚毛的排列模式以及瓣膜超微结构方面与该复合体的其他成员（即群居角毛藻和冷角毛藻）相似。唯一可用于区分该复合体物种的形态特征是与休眠孢子形态相关的方面。这两个新描述的物种彼此密切相关，在分子系统发育中与冷角毛藻形成姐妹分支。我们还提供了与群居角毛藻复合体有遗传关系的放射角毛藻和辛氏角毛藻的系统发育地位以及形态特征。
