【摘要】 多环马格里夫藻是一种世界性广泛分布的有毒有害藻华原因种。过去30多年里多环马格里夫藻藻华在许多国家频繁暴发且呈快速扩散趋势。过去的研究根据不同地理来源种群在核糖体大亚基基因序列的显著差别,将其分成4种不同核糖体型(ribotype),即东亚型、菲律宾型、美国/马来西亚型和地中海型。但是,不同核糖体型的种群在形态和超微结构上是否也存在可辨识差异尚未见深入研究。为此,本文对从中国青岛胶州湾、美国东海岸和马来西亚近海分离的三株多环马格里夫藻(中国株MPJZBC3、美国株CP1和马来西亚株MPCoKK23)的细胞表面形态和超微结构进行了比较研究,并进一步基于核糖体大亚基序列进行了分子系统学分析。结果首先证明了分离自胶州湾的多环马格里夫藻属于东亚核糖体型,而美国株和马来西亚株均属美国/马来西亚型(中国株与美国株及马来西亚株在1523个碱基的核糖体大亚基序列上相似性为93.6%)。但是,在所有常用的具有分类学意义的细胞形态学和超微结构特征上[细胞大小、单细胞或群体及群体细胞数、上下锥形状、横沟位移度(绕细胞圈数)、纵沟形态、顶沟形态、细胞核位置与形状、染色体形状与数目、叶绿体的形状、结构、数目及分布、淀粉核形态等],中国株与美国株和马来西亚株(也即东亚核糖体型和美国/马来西亚核糖体型)都没有明显可区分的差别。因此,我们认为应该在生活史、休眠孢囊形态和生理学特征(如毒素种类及毒性强弱)以及性别相容性(sexualcompatibility)等方面开展进一步比较研究,以获得对不同核糖体型种群的识别性状。在现阶段有害藻华的野外监测中,尤其是对于不同核糖体型种群可能造成的生物入侵的监测和追溯,多环马格里夫藻的鉴定尚必须以核糖体基因序列作为可靠的判决依据。更多还原

【Abstract】 Margalefidinium polykrikoides, a toxic and harmful algal blooms-forming dinoflagellate, is widely distributed in the coastal waters worldwide. In the past 30 years, M. polykrikoides blooms have been frequently observed in many countries and regions covering Asia, America, and Europe, and rapidly expand its geographic distribution. Previous studies have shown that there are different geographical populations of M. polykrikoides around the world, which are in fact genetically different in the large subunit(LSU) rRNA gene, and thus they are classified into 4 different ribotypes based on their differences in LSU rDNA sequences, namely, 1) East Asian ribotype, 2) Philippines ribotype, 3) American/Malaysian ribotype, and 4) Mediterranean ribotype. However, there has been no detailed morphological and ultrastructural comparison among the populations of these ribotypes and thus it is unknown about whether these populations can be distinguished from each other with any discernible morphological difference. Therefore, we compared in this study the morphological and ultrastructural features among three strains of M. polykrikoides(MPJZBC3, CP1 and MPCoKK23) that were isolated from Jiaozhou Bay, China; the Peconic Bay of New York, the USA; and Kota Kinabalu, Malaysia, respectively. The molecular phylogeny was also carried out based on the partial sequences of LSU rRNA gene. First, the results show that the strain MPJZBC3 belongs to the East Asian ribotype, and the American and Malaysian strains both belong to the American/Malaysian ribotype(the similarity between the Chinese strain and the USA strain or the Malaysian strain is 93.6%, i.e. 1426 bp/1523 bp). However, in all diagnostic characteristics in morphology and ultrastructure(cell size, single cell or colony and the number of cells in a colony, shapes and relative sizes of the epicone and hypocone, cingular displacement(the number of turns of cingulum encircling the cell), shape of the sulcus, structure of the apical groove, position and shape of the nucleus, shape and number of chromosomes, shape, ultrastructure, and number of chloroplasts and pyrenoids, etc.), there was no discernible difference observed among the three strains, or between the East Asian and American/Malaysia ribotype. Therefore, we propose that further comparative studies need to be conducted on the life history, morphology of resting cysts, stable physiological characteristics such as toxin species and the intensity of toxicity, and the sexual compatibility among these ribotypes in order to obtain identification traits of these ribotypes. At present, identification of M. polykrikoides ribotypes in the field monitoring of harmful algal blooms must be based on the LSU rDNA sequencing.更多还原