我国3个新记录海链藻种类的形态学研究

MORPHOLOGICAL STUDIES ABOUT THREE NEWLY RECORDED THALASSIOSIRA SPECIES FOR CHINA

利用光镜(LM)和扫描电镜(SEM)技术,对采自我国沿海海域的自然水样,以及分离获得的单克隆培养藻株进行了形态学观察,针对其中的海链藻属Thalassiosira Cleve种类开展了形态分类学的专题研究。报道了3个新记录种类,分别是安达曼海链藻Thalassiosira andamanica Gedde、缢缩海链藻Thalassiosira con-stricta Gaarder和双线海链藻Thalassiosira duostra Pienaar。对每个种类的形态学特征、生活习性和生态分布进行了描述,提供了光镜和电镜照片,并对相似种类的形态学特征进行了比较研究。

Thalassiosira Cleve is a very common diatom genus with high species diversity in coastal waters around the world. Up to now, nearly one hundred and fifty taxa belonging to this genus have already been reported. Thalassiosira is the main contributor to nano-phytoplankton assemblage because cell sizes of most species are below 20 μm. Previously, some Thalassiosira species were considered as model organisms of centric diatoms and Bacillariophyta, and many studies concerning genetics, sexual reproduction, feeding pressure, impact on egg producing and hatching of zooplankton, envi ronmental indicator, etc, have been performed. On the other hand, some Thalassiosira species are also important bloom-causing organisms. And the blooms induced by T. curviseriata and T. diporocyclus have already been reported in the Changjiang River Estuary and along Hainan coast respectively. Due to their very small cell sizes, electron microscopy is needed for accurate identification. In order to characterize the species diversity and distribution of the genus Thalassiosira along Chinese coastal waters, water samples were collected from some locations. Thalassiosira specimens within these samples, as well as several clonal strains isolated from natural samples, were studied by light microscopy （LM） and scan- ning electron microscopy （SEM）. All samples were fixed with Lugo＇s solution and were concentrated to a final volume about 2-10 mL by settling overnight several times. The cultivated samples could be observed and analyzed under a light microscope. For observation under scanning electron microscope, sub samples were taken and treated in several steps. Firstly, after dropped into the same volume of concentrated H2SO4, these samples were boiled in the water bath for about 10-15 minutes to remove the organic materials. Secondly, these samples were washed to neutrality with distilled water for several times. Then, these samples were coated with gold and were subsequently observed, identified and photographed under a scanning electron microscope. Three Thalassiosira species were newly recorded species for China, i.e., T. anda-manica Gedde, T. constricta Gaarder and T. duostra Pienaar. Along with LM and SEM photos, detailed morphological de scription, habits and ecological distribution of these species were given in this paper. Simultaneously, taxonomic compari son among resembling species were made. T. andamanica was very common in South China Sea coast, especially in Hong Kong waters. The morphological features of this species were represented by prominent external tubes of all fultoportulae and one rimoportula keeping a distance from the valve margin. For T. duostra, more patterns of valve fultoportulae and three marginal rimoportulae have been found, which were different from previous descriptions.