Faculty of Science, Department of Biology, University of Zagreb, Rooseveltov trg 6, Zagreb, 10000, Croatia.
Marine and Continental Waters Program, Institute for Food and Agricultural Research and Technology (IRTA), Sant Carles de la Ràpita, Spain.
J Phycol. 2021 Feb;57(1):143-159. doi: 10.1111/jpy.13085. Epub 2020 Dec 15.
The paraphyletic diatom genus Nitzschia comprises over 1000 morphologically distinct pennate taxa, known from the benthos and plankton of freshwater, brackish, and marine environments. The principal diagnostic characters for delimitation of Nitzschia species include valve shape, the position and structure of the raphe, presence/absence and shape of the proximal raphe endings and terminal raphe fissures, areola structure, and specific morphometric features such as cell size, and stria and fibula density. In this study, we isolated 12 diatom strains into culture from samples collected at the surface or greater depths of the southeastern Adriatic Sea. Morphological analyses included LM, SEM, and TEM observations, which, along with specific morphometric features, allowed us to distinguish three new Nitzschia species. These findings were congruent with the results of phylogenetic analyses performed on nuclear-encoded SSU (18S) rDNA and chloroplast-encoded rbcL and psbC genes. One of the new species (Nitzschia dalmatica sp. nov.) formed a lineage within a clade of Bacillariaceae containing members of the Nitzschia sect. Dubiae, which was sister to Psammodictyon. A second lineage was part of a novel clade that is significantly distinct from other Nitzschia species sequenced so far and includes Nitzschia adhaerens sp. nov. and N. cf. adhaerens. A further new species was found, Nitzschia inordinata sp. nov., which appeared as the sister group to the N. adhaerens clade and the conopeoid Nitzschia species in our phylogenetic trees. Our findings contribute to the overall diversity of genus Nitzschia, especially in identifying some deep branches within the Bacillariaceae, and highlight under-scoring of this genus in marine plankton.
后生体型的菱形藻属（Nitzschia）包含超过 1000 种形态上不同的羽纹硅藻，分布于淡水、半咸水和海洋环境的底栖和浮游生物中。后生体型的菱形藻属物种的主要鉴别特征包括壳面形状、脊缝的位置和结构、近脊缝末端和端脊裂缝的有无和形状、相连纹孔区的结构以及特定的形态特征，如细胞大小、纹和脊突的密度。在本研究中，我们从东南亚得里亚海表面或更深的样本中分离出 12 株硅藻培养物。形态分析包括 LM、SEM 和 TEM 观察，这些观察结果以及特定的形态特征使我们能够区分出三种新的菱形藻物种。这些发现与核编码 SSU（18S）rDNA、叶绿体编码 rbcL 和 psbC 基因的系统发育分析结果一致。其中一个新物种（Nitzschia dalmatica sp. nov.）形成了 Bacillariaceae 中的一个分支，该分支包含 Nitzschia 节 Dubiae 中的成员，与 Psammodictyon 为姐妹群。另一个分支是一个新的分支，与迄今为止测序的其他菱形藻物种明显不同，包括 Nitzschia adhaerens sp. nov.和 N. cf. adhaerens。还发现了另一个新物种，Nitzschia inordinata sp. nov.，它与 N. adhaerens 分支和我们的系统发育树中的 Conopeoid Nitzschia 物种为姐妹群。我们的研究结果丰富了菱形藻属的总体多样性，特别是在鉴定 Bacillariaceae 中的一些深分支方面，同时也强调了该属在海洋浮游生物中的重要性。
