泰国近海习见有毒立方水母和钵水母的遗传分析

本研究利用线粒体16S rDNA和核基因18S rDNA片段,对泰国沿海常见的有毒水母进行遗传分析,并比较了2个基因片段作为通用分子标记,在研究水母类多个纲的遗传多样性中的应用。研究发现,泰国近海的有毒水母存在较高的遗传多样性,所获得的32个样品可以分为9个种,包括4种钵水母、4种立方水母和1种水螅水母。然而,完全确定各种的分类地位,还需要更多的形态、生活史等方面信息。两个基因片段均能明确区分各种类,但核基因18S序列比线粒体基因片段更为保守。根据16S基因片段序列计算水母种内和种间的K2P(Kimura 2-parameter)遗传距离,发现所研究的9个水母种类,种内遗传距离在0~0.050之间,其中94%的种内遗传距离小于0.040,同纲种间的遗传距离为0.204~0.474,其中91%的种间遗传距离大于0.250;而利用18S基因,种内距离在0~0.002之间,同纲种间距离为0.008~0.066(平均为0.038,SE=0.006)。16S的AT碱基含量明显高于核基因18S,且16S的碱基含量在不同纲之间有显著差异,进一步表明水母线粒体16S基因的突变率相对较高,适合研究水母较低分类阶元以及种下的遗传差异。

Genetic analysis of common venomous Cubozoa and Scyphozoa in Thailand waters

The genetic diversity of common venomous Cubozoa and Scyphozoa jellyfish in the coastal waters of Thailand was investigated using the nuclear 18S and mitochondrial 16S rDNA genes. It was also compared about the capability of these two molecular markers to discriminate those common jellyfish species. There were 9 genetically distinctive species among the 32 samples collected from Thai waters, including 4 Cubozoa species, 4 Scyphozoans and 1 hydrozoan. However, it needs further information on the morphology and life cycle to determine the true taxonomic status of most species in this research. The K2P (Kimura 2-parameter) genetic distance was evaluated within and among the species based on the sequences of these two genes. The results showed much higher genetic divergence based on 16S gene (0－0.050 and 0.204－0.474 for intra-and inter-species genetic distances, respectively) compared with those using 18S gene (0－0.002 and 0.008－0.066 for intra-and inter-species genetic distances, respectively). At the same time, the A and T nucleotide composition of 16S gene was obviously higher than 18S gene. And significant variation of nucleotide composition was detected between two jellyfish classes using 16S gene, but not 18S gene. These results further indicated the relatively higher mutation rate of 16S gene, which could be applied for the genetic diversity studies among jellyfish species with close genetic relationship and the intra-species genetic population studies.