Franco Andréa de Oliveira da Rocha, They Ng Haig, Canani Luis Gustavo de Castro, Maggioni Rodrigo, Odebrecht Clarisse
Institute of Oceanography, Federal University of Rio Grande - FURG, Av. Itália, km8, CEP 96203-900, Rio Grande, Brazil.
Department of Oceanography and Limnology, Federal University of Rio Grande do Norte-UFRN, Av. Senador Dinarte de Medeiros Mariz, s/n, Praia de Mãe Luiza, CEP 59014-002, Natal/RN, Brazil.
J Phycol. 2016 Oct;52(5):888-895. doi: 10.1111/jpy.12435. Epub 2016 Aug 31.
The diatom Asterionellopsis glacialis sensu lato forms high-density patches in the surf zone of some sandy beaches worldwide and was until recently considered a cosmopolitan species. With the recent description of four cryptic species, the identity of specimens found in these accumulations remains uncertain. In this study, diatom patches were sampled from two sandy beaches of the Brazilian coast: one tropical (Futuro Beach, 3° S; 38° W) and one subtropical (Cassino Beach, 32° S; 52° W). Fine structure of frustules and the sequencing of three phylogenetic markers revealed the subtropical strains to be A. guyunusae and the tropical strains to be a new species, here described as Asterionellopsis tropicalis sp. nov. A. tropicalis was differentiated morphologically by the number of striae in 10 μm at the foot pole and head (39-44; 38-45, respectively), from A. lenisilicea (46-55; 46-64), A. maritima (46-51; 46-60), and A. thurstonii (42-58; 55-70). The number of striae at the head region of the valvocopula (10 μm) helped to distinguish A. tropicalis (56-62) from A. guyunusae (61-64), but A. tropicalis was morphologically undistinguishable from A. glacialis. The sequence divergence from other identified Asterionellopsis species was 13%-16% (Cox1), 11%-12% (5.8S + ITS2) and 2%-6% (RbcL), and A. tropicalis formed a distinct monophyletic clade with high support in all analyzed phylogenetic trees (single or multi-locus). This work will aid in the understanding of the ecological and physiological diversity of diatom patches that are key to the trophic webs of sandy beaches.
广义的冰河星脐藻（Asterionellopsis glacialis）在全球一些沙滩的冲浪区形成高密度斑块，直到最近它都被视为一个世界性物种。随着最近对四个隐存种的描述，在这些聚集体中发现的标本的身份仍不确定。在本研究中，从巴西海岸的两个沙滩采集了硅藻斑块样本：一个是热带沙滩（未来海滩，南纬3°；西经38°），另一个是亚热带沙滩（卡西诺海滩，南纬32°；西经52°）。硅藻壳的精细结构和三个系统发育标记的测序表明，亚热带菌株是古云星脐藻（A. guyunusae），热带菌株是一个新物种，在此描述为热带星脐藻（Asterionellopsis tropicalis sp. nov.）。热带星脐藻在形态上通过足极和头部10μm内的条纹数量（分别为39 - 44；38 - 45）与细纹星脐藻（A. lenisilicea，46 - 55；46 - 64）、海洋星脐藻（A. maritima，46 - 51；46 - 60）和瑟斯顿星脐藻（A. thurstonii，42 - 58；55 - 70）相区分。瓣壳联结处头部区域（10μm）的条纹数量有助于将热带星脐藻（56 - 62）与古云星脐藻（61 - 64）区分开来，但热带星脐藻在形态上与冰河星脐藻无法区分。与其他已鉴定的星脐藻物种的序列差异为13% - 16%（细胞色素氧化酶亚基I，Cox1）、11% - 12%（5.8S + ITS2）和2% - 6%（核酮糖-1,5-二磷酸羧化酶大亚基，RbcL），并且热带星脐藻在所有分析的系统发育树（单基因或多基因座）中都形成了一个具有高支持度的独特单系分支。这项工作将有助于理解硅藻斑块的生态和生理多样性，而硅藻斑块是沙滩营养网的关键。
