两种大眼蟹线粒体12S rRNA基因序列的比较研究

Sequence Comparison of Mitochondrial 12S rRNA Genes between Two Crab Species,Macrophthalmid dilatatum and M. japonicus

测定了宽身大眼蟹和日本大眼蟹线粒体12S rRNA基因部分片段的序列,前者为577 bp,后者为572 bp。二者的核苷酸序列A、T、G、C的含量相似,分别为39.0%、35.7%、16.5%、8.8%;39.3%、36.2%、15.8%、8.7%;不包括11处插入/缺失位点,两序列间有75个变异位点,核苷酸差异率为13.18%,其中转换42个、颠换33个,转换与颠换比约为1.3。对国内外4种大眼蟹长度为331bp的12S rRNA基因同源序列进行分析,A+T的平均含量为76.6%,明显高于G+C的平均含量,且存有变异位点52个,简约信息位点25个。系统发生树的拓扑结构显示,所有的大眼蟹聚为一支,支持大眼蟹类为一单系。

Partial sequences of the mitochondrial 12S rRNA gene were determined for two species crabs, Macrophthalrnus dilatatum and M. japonicus. The results showed that the 12S rRNA gene had 577 bp for M. dilataturn and 572 bp for M. japonicus with similar contents of A（39.0 % for M. dilataturn; 39. 3 % forM. japonicus）, T（35.7 %, 36.2 %）, G（16.5 %,15.8 %）and C（8.8 %,8.7 %）. There were 75 different sites（except 11 deletion/insertion sites）between the two species, including 42 transition sites and 33 transversion sites. It was found that the si/sv and ratio of different sites were about 1.3 and 13.18 %, respectively. Furthermore, 331 bp homologous segments were analyzed to discuss the phylogenetie relationship between four Macrophthalmid crabs and other 23 Ocypodoid crabs in the world. The results showed that the average A＋T content（76.6%）was higher than G＋C, and there were 52 variable sites and 25 parsimony-information sites in the nucleotides of the four Macrophthalmid crabs data. Neighbor-Joining method revealed that topological structure of the molecular phylogenetic tree constructed by 12S rRNA gene in all species of Macrophthalmid crabs were clustered into one distinct elade, indicating that the monophyly of Macrophthalmid crabs was well supported.