海鲢细胞色素b基因的序列分析

Analysis on Sequences of Cytochrome b Gene of Chinese Elops

[目的]分析中国海鲢的分类地位。[方法]从浙江、海南和广东3个地区的4尾海鲢中提取DNA,测定其线粒体细胞色素b（Cytb）基因部分序列,结合GenBank中Elops hawaiensis、E.saurus和E.affinis的相关序列,采用Kimura 2-parameter模型计算各类群间的遗传距离,并以大海鲢为外类群,用邻接法构建系统发育树。[结果]海鲢Cytb 5′端646 bp同源序列中A＋T的含量（51.9%）高于G＋C含量（48.1%）;变异位点有29个,其中单碱基变异位点24个,简约信息位点数为5;转换/颠换比〉4.0。在分子系统树上,中国海鲢与E.hawaiensis以98%的自展置信值聚为一支,然后与E.saurus成姐妹群。中国海鲢与E.saurus和E.affinis遗传距离分别为0.013-0.015和0.034-0.035,处于3个已知种的种间水平,而与E.hawaiensis间遗传距离为0.000-0.004,比自身之间的遗传距离还要小。[结论]推测中国东南沿海的海鲢或为E.hawaiensis。

[Objective] The study aimed to analyze the classification status of Chinese Elops.[Method] DNA was extracted from 4 fishes of Elops sampled from 3 areas of Zhejiang and Hainan and Guangdong and their partial sequences of mitochondrial Cytochrome b gene（Cytb） were detected.Combined with homologous sequences of Elops.hawaiensis,E.saurus and E.affinis downloaded from Genbank,the genetic distances among various groups were computed on base of Kimura 2-parametre model.With Megalops as the outgroup,the phylogenetic tree was constructed by neighbor-joining（NJ） method.[Result] Among the homologous sequences in Cytb 5＇ end with 646 bp the content of A and T（51.9%） was higher than that of G and C （48.1%）.There were 29 nucleotide sites substituted,of which 24 were single base variable sites and 5 were parsim-information sites.The ratio of transitional pairs versus transversional pairs was more than 4.0.In the phylogenetic tree,Chinese Elops and E.hawaiensis were clustered into one clade with high bootstrap confidence value of 98%,and the clade was sister group to E.saurus E.affinis was at the basal position.The genetic distances between Chinese Elops and E.affinis ranged from 0.034 to 0.035,and those between Chinese Elops and E.saurus varied from 0.013 to 0.015,both of which were within interspecies genetic distances level of 3 known species.The genetic distances between Chinese Elops and E.hawaiensis were 0.000～0.004,even smaller than intraspecies genetic distances within Chinese Elops.[Conclusion] Phylogenetic analyses suggested that Elops in Southeast China may be E.hawaiensis.