四川宜宾产桃花水母的线粒体CO I序列片段分析

目的：针对桃花水母形态分类中存在的一些混乱和矛盾，引入分子生物学方法阐明其分类难题。方法：采用PCR和DNA测序技术，对四川宜宾产桃花水母标本的线粒体细胞色素C氧化酶亚基Ⅰ基因（mitochondrial cytochrome c oxidase subunitⅠ，COⅠ）片段进行了扩增与测序，并与GenBank中已有的淡水水母目COⅠ基因序列进行比对分析，利用MEGA 5计算它们的遗传距离，构建NJ树。结果：该桃花水母标本与索氏桃花水母Craspedacusta sowerbii的COI基因相似度极高，同源性在99%以上，遗传距离为0.003，在进化树中与索氏桃花水母聚为同一支。结论：该标本属于索氏桃花水母。

Sequence analyses of mitochondrial cytochrome c oxidase subunitⅠgene fragment of freshwater jellyfish from Yibin,Sichuan

objective：Molecular biological method was introduced to clarify the difficult classification problem of freshwater jellyfish （Craspedacusta sowerbii）. Methods：The mitochondrial cytochrome c oxidase subunit Ⅰ （COⅠ） gene of freshwater jellyfish （from Yibin, Sichuan） was amplified by polymerase chain reaction （PCR） and then sequenced. Aligning with other Limnomedusae species retrieved from GenBank, genetic distance among species was calculated by using the Kimura-2-parameter （K2P） method in MEGA 5. Neighbor-Joining （NJ） tree based on K2P distances was created to provide a graphic representation of the divergence patterns for among-and within-species. Results：The result showed that COI sequence of freshwater jellyfish was highly similar to those of C. sowerbii （similarity 99%）. The genetic distance between the sample and C. sowerbii was 0.003. The NJ tree showed 100%degree of confidence cluster of our sample and C. sowerbii from Germany. Conclusion：Our sample is C. sowerbii.