硅藻中国新记录种——帕瓦拉桥弯藻

Cymbella pavanaensis A. Vigneshwaran et al., a diatom reported for the first time in China

关键词:  桥弯藻属, 顶孔区, 孤点, 超微结构, 新记录

Key words:  Cymbella Agardh, apical pore field, stigma, ultrastructure, new record

摘要:

在对湖南省硅藻多样性研究过程中,发现其中一采自湘江的桥弯藻种类具有以下鉴定特征:(1)细胞小,长度小于29 μm;(2)壳面略微呈背腹之分;(3)远缝端末梢向壳面背侧弯曲;(4)顶孔区很小,由1～3横列形态不同的两种类型孔纹组成,一种孔纹与壳面上的孔纹相似,呈狭缝隙状,另一种为圆形小孔,其内部开口上方有袋盖状硅质突出物覆盖;(5)壳面背侧中部处线纹密度每10 μm为10～12条、腹侧中部处每10 μm为11～13条,孔纹密度每10 μm为30～40个;(6)在靠近壳面腹侧中央区具有1～2个孤点。经与帕瓦拉桥弯藻(Cymbella pavanaensis A. Vigneshwaran et al.)模式种群相比较,该文确定上述桥弯藻即为帕瓦拉桥弯藻。该文提供了对帕瓦拉桥弯藻超微结构的更多清晰认识,扩大了其地理分布区域,且是该种在中国的首次报道。

Abstract:

During the process of studying the diatom diversity of Hunan Province, we find that a Cymbella species collected from Xiang River possesses the following diagnostic features:(1)Cells are small and their lengths are less than 29 μm;(2)Valves exhibit slight dorsiventrality;(3)Distal raphe fissures are dorsally deflected;(4)Apical pore fields are very small and composed of 1-3 transapical rows of porelli, which comprise two forms, one is slit-like, similar to the areolae on the valve face, and the other is rounded with internal openings covered by the flap-like silica projections;(5)Striae 10-12/10 μm at the dorsal middle part, 11-13/10 μm at the ventral middle part, and areolae 30-40/10 μm;(6)And 1-2 stigmata exist near the valve ventral central area. After comparing this species with the type population of Cymbella pavanaensis A. Vigneshwaran et al., in this paper, it is identified as C. pavanaensis. This paper provides a clearer knowledge of the ultrastructure of C. pavanaensis, enlarges its geographical distribution region, and reports it for the first time in China.