双壳缝硅藻中国2新记录种——肿胀类辐节藻和英格兰盘状藻具孤点变种

Two Biraphid Diatom Species Reported from China for the First Time——Prestauroneis tumida and Placoneis anglophila var.signata

该研究利用光学和扫描电子显微镜,对采自东洞庭湖国家自然保护区的2种双壳缝硅藻中国新记录种——肿胀类辐节藻和英格兰盘状藻具孤点变种的标本进行了详细形态学研究。观察发现:(1)肿胀类辐节藻具有4个鉴定特征:①壳瓣轮廓在大的标本中呈披针形,在小的标本中呈椭圆披针形;②线纹在壳面中部呈辐射状排列,彼此间隔相对较宽;③假隔片在壳面两端都存在;④孔纹在内壳面被具微孔的膜完全覆盖。(2)英格兰盘状藻具孤点变种也具有4个鉴定特征:①壳瓣线性椭圆形或椭圆形;②线纹除了在壳面两端呈平行排列外,在壳面大部区域呈辐射状排列,中部线纹密度10~14条/10μm;③在壳面中央有一个孤点;④孔纹内部开口被由4个支柱支撑的孔板所覆盖,孔纹密度35~40个/10μm。该研究的详细描述和清晰的插图为肿胀类辐节藻和英格兰盘状藻具孤点变种的准确鉴定提供了参考。

This paper thoroughly studies the specimens of two biraphid diatom species reported from China for the first time——Prestauroneis tumida and Placoneis anglophila var.signata,which were collected from the East Dongting Lake National Nature Reserve,were studied with light and scanning electric microscopy.The results show that:(1)Pr.tumida possesses four identifying characters:①valve outline lanceolate in larger specimens,and elliptic-lanceolate in smaller specimens;②striae radiate on the middle valve part and spaced wider than on other parts;③a pseudoseptum occurring at both apices;④the inner areola openings covered by hymens.(2)Pl.anglophila var.signata also possesses four identifying characters:①linear-elliptic or elliptic valve outline;②striae radiate in most middle part where stria density is 10-14/10μm,except at the apices where striae are parallel;③a stigma present at the center of the valve;④the internal areola opening covered by a velum which is supported by four props and the areola density is 35-40/10μm.The detailed descriptions and clear illustrations in this paper provide a basis for the correct identification of Pr.tumida and Pl.anglophila var.signata for the future researchers.