两种大眼蟹线粒体16S rRNA基因序列分析

Sequence analyses of mitochondrial 16S rRNA gene between two species of macrophthalmid crabs

测定了宽身大眼蟹和日本大眼蟹线粒体16SrRNA基因部分片段的序列,其长度均为517bp。二者的核苷酸序列A,T,G,C的含量相似:宽身大眼蟹分别为33.3%,35.6%,19.9%,11.2%;日本大眼蟹分别为35.2%,35.4%,18.4%,11.0%。不包括6处插入/缺失位点,两序列间有63个变异位点,核苷酸差异率为12.26%,其中转换32个、颠换31个,转换与颠换比约为1.0。对国内外大眼蟹的24条长度为415bp的16SrRNA基因同源序列进行分析,A+T的平均含量为71.7%,明显高于G+C的平均含量,且存有变异位点171个,简约信息位点137个。中国和日本的日本大眼蟹之间的核苷酸差异率为4.42%,表明二者已有明显的遗传分化;中国的日本大眼蟹与日本的万岁大眼蟹之间的核苷酸差异率仅为0.21%,表明二者有可能为同一物种。上述结果得到了系统发生树拓扑结构的支持。

Partial sequences of the mitochondrial 16S rRNA gene were determined for two Macrophthalmus species （M. dilatatum and M. japonicus）, and the sequence length of the two species was the same. Of the 517 nucleotides obtained, the A, T, G and C contents were similar, which were 33.3%, 35.6%, 19.9%, 11.2% and 35.2%, 35.4%, 18.4%, 11.0% respectively. There were 63 different sites （excluding 6 deletion/insertion sites） between the two species, including 32 transition sites and 31 transversion sites. The si/sv and ratio of sequence divergence were about 1.0 and 12.26% respectively. Furthermore, 24 of 415bp homologous segments were analyzed to discuss the phylogenetic relationship of macrophthalmid crabs in the world. The results showed that the average A＋T content （71.7%） was higher than G＋C content, and there were 171 variable sites and 137 parsimony-information sites in the nucleotides of the macrophthalmid crabs data. The ratios of sequence divergence were 4.42% and 0.21% between Chinese and Japanese M. japonicus, and between Chinese M. japonicus and Japanese M. banzai respectively. The results revealed that there was significance genetic difference between Chinese and Japanese M. japonicus, and Chinese M. japonicus and Japanese M. banzai may be a single species. The conclusion was supported by the topological structure of the molecular phylogenetic tree, constructed by 16S rRNA gene with Neighbor-Joining method.