三种沼虾的COI基因序列变异及其分类地位探讨(英文)

Mitochondrial COI Gene Sequence Variation and Taxonomic Status of Three Macrobrachium Species

罗氏沼虾(Macrobrachium rosenbergii)和日本沼虾(M.nipponense)已经在我国得到广泛的养殖,产生巨大的经济效益。祁连沼虾(M.qilianensis)是自然分布在我国甘肃省的土著虾种,因其外部形态符合沼虾属的特征,而被前人归入沼虾属。为了从分子生物学的角度理解罗氏沼虾、日本沼虾与祁连沼虾的遗传差异,为合理开发和利用沼虾资源提供理论基础,作者对这3种沼虾的线粒体COI基因序列进行研究。从甘肃、浙江等地分别采集这三种沼虾的样本各10尾,共30尾,其中祁连沼虾是野生样本,而罗氏沼虾和日本沼虾都是养殖样本。通过PCR方法扩增线粒体COI基因,并测序。通过比对,获得一致序列649bp。在30个样本中共检测到169个变异位点,占总变异的26.04%;共检测到7种单倍型。3种沼虾的核苷酸多态性分别为:罗氏沼虾0.411%、日本沼虾0.092%、祁连沼虾0.031%。野生的祁连沼虾遗传多样性远远低于养殖的罗氏沼虾和日本沼虾。三种沼虾单倍型之间的Kimura双参数遗传距离在19.87%～23.84%,三者之间的遗传距离较大,提示三者均为有效种。为进一步确定这三种沼虾在长臂虾科的分类地位,我们从NCBI数据库中下载了长臂虾科的其它种类的COI序列进行系统发生分析。用NJ法构建的分子系统树显示:日本沼虾和罗氏沼虾与沼虾属的其它种类聚成一枝,而祁连沼虾与同亚科的脊尾白虾(Exopalaemon carinicauda)和长角长臂虾(Palaemon debilis)较沼虾属另10种虾的遗传距离近,即祁连沼虾与白虾属及长臂虾属聚成另一枝。因此,COI序列的结果不支持祁连沼虾归入沼虾属。但其分类地位应该综合多方面证据重新进行分析确定。

Freshwater prawns （Decapoda： Caridea： Macrobrachium） play an important role in domestic fishery resources. Culturing M. rosenbergii and M. nipponense brings great economic benefits, as the two species were widely farmed in China. M. qilianensis, a native species with natural distribution limited in Gansu province, was classified into genus Macrobrachium based on external morphological characters. In order to understand the molecular genetic differences among the three species of Macrobrachium, i.e., M. rosenbergii, M. nipponense, and M. qilianensis, we analyzed sequences of mitochondrial cytochrome oxidase subunit I （COI） of them. It would provide theoretical basis of exploiting and utilizing Macrobrachium resources rationally. A total of 30 individuals （10 individuals of each species） were collected from Gansu and Zhejiang province. Samples of M. qilianensis were wild, however, that of M. rosenbergii and M. nipponense were cultured. Their mitochondrial COI gene segment sequences were obtained by using the method of PCR amplification and sequencing. After alignment, 649 bp consensus sequences of COI were obtained. One hundred and sixty-nine variable sites were detected in all 30 individuals, accounting for 26.04% of total sequence. A total of seven haplotypes were also detected. Nucleotide diversity was 0.411% within M. rosenbergii, 0.092% within M. nipponense, and 0.031% within M. qilianensis. Genetic diversity of wild M. qilianensis was much lower than that of cultured M. rosenbergii and M. nipponense. Genetic distances between different haplotypes of the three prawns ranged from 19.87% to 23.84%. It suggested that the three species were valid species, because genetic distances among them were quite great. To further determine the taxonomic status of the three prawns in family Palaemonoidae, we downloaded the corresponding COI sequences of Palaemonoidae prawns from Genbank and analyzed the phylogenetic relationships of them. Phylogenetic tree （NJ） showed that M. nipponense, M. rosenbergii and other Macrobrachium species constituted one monophyletic group. However, M. qilianensis, Exopalaemon carinicauda, and Palaemon debilis formed the other clade. Thus, results of COI sequences did not support that M. qilianensis belonged to genus Macrobrachium. The taxonomic status ofM. qilianensis should be reevaluated with more comprehensive evidences.