瓶鼻海豚、中华白海豚和糙齿海豚线粒体16S rRNA基因的序列分析

Sequence analysis of mitochondrial 16S rRNA of three dolphin species,Tursiops truncatus,Sousa chinensis and Steno bredanensis

采用聚合酶链式反应(PCR)技术扩增瓶鼻海豚、中华白海豚和糙齿海豚的线粒体DNA16S rRNA基因,获得了大约600bp的片段。扩增产物直接测序,去除引物序列后分别获得515、519和529bp的核苷酸片段。碱基组成平均为T25·8%,C20·7%,A32·1%,G21·4%,GC含量为42·1%。与35种鲸豚类的55条同源序列比对,去除部分端部序列后得到497个比对位点,包括14个插入/缺失位点和127个变异位点(104个简约信息位点,23个单突变子)。序列比较表明,我国水域的瓶鼻海豚和中华白海豚与国外种存在一定的差异。NJ聚类分析结果与目前的主流观点基本相同,即须鲸亚目形成单系群而齿鲸亚目则为多系群,后者包括海豚总科、抹香鲸总科、喙鲸总科和淡水豚总科。其中抹香鲸总科与须鲸亚目聚合在一起,然后与海豚总科聚合再与喙鲸总科相聚。淡水豚总科为一并系群并处于整个鲸豚类的基部,其中恒河豚科是最早分化的一支。但在海豚总科中,鼠海豚科的江豚则与一角鲸科的白鲸聚合一起,与形态分类不同。

Mitochondrial 16S rRNA gene fragments were amplified from dolphins Tursiops truncatus, Sousa chinensis and Steno bredanensis using PCR technique. The PCR products were about 600 bp and were directly sequenced subsequently. Finally, 515,519 and 529 bp unambiguous nucleotide sequences were obtained respectively after excluding the primer sequences. The average base compositions were T 25.8%, C 20. 7%, A 32. 1% and G 21.4% with GC content being 42. 1%. Alignment with 55 homologous sequences from 35 cetacean species in GenBank revealed 14 insertion/deletions and 127 variable sites （ 104 parsimony-informative sites and 23 singletons） among 497 truncated alignment sites. Sequence comparison suggested that Chinese T. truncatus and S. chinensis are different from the corresponding species abroad. NJ cluster analysis indicated that subclass Mysticeti is a monophyly whereas subclass Odontoceti is a polyphyly, including Delphinoidea, Physeteroidea （ sperm whales）, Ziphioidea and Platanistoidea. The sperm whales in Odontoce-ti was closely related with baleen whales in Mysticeti, and then clustered with Delphinoidea and then with Ziphioidea. The Platanistoidea was paraphyletic and located at the base of the tree, among which Platanistidae constitutes the base clade. Neophocaena phocaenoides （Phocoenidae） clustered with Delphinapterus leucas （Monodontidae） in Delphinoidea, inconsistent with morphological classification.