Genetic Diversity And Phylogeny Analysis Of Octopus Variabilis In China Coastal Waters

In this paper, genetic variation of 7 wild populations of Octopus variabilis and the phylogeny of nine species of Genus Octopus in China coastal waters were investigated by applying mitochondrial gene sequencing technology and AFLP technology. The samples were collected from Dalian, Yaitai, Qingdao, Lianyungang, Zhoushan, Wenzhou and Xiamen, respecttively. The main results were shown as follows:Mitochondrial 16S rRNA gene fragments were amplified and sequenced from 4 wild populations of O. variabilis. Genetic variation was analyzed using 512 bp segments of 16S rRNA gene, among which 48 polymorphic sites were detected. 30 haplotypes were detected out of 45 individuals. According to the UPGMA phylogenetic tree, four O. variabilis populations can be divided into two lineages, one consisting of Dalian, Qingdao and Zhoushan populations and the other consisting of Xiamen population. The genetic distances between the population of XM and others reached 0.094 and the genetic fixation index and gene flow reached 0.97 and 0.02, respectively. The results showed considerable genetic isolation among XM and other populations. Maybe they were different subspecies.The sequences of mitochondrial COI gene fragment of O. variabilis collected from 7 localities in China coastal waters were analyzed. Results showed that, compared with other cephalopod species, O. variabilis showed higher genetic diversity in populations. 74 polymorphic sites were detected in 635bp aligned sequence, which represented for 11.7 % of the total length of sequenced COI gene. 25 haplotypes were detected out of 108 individuals from these 7 populations. Molecular variance analysis revealed strong genetic structure in 7 O. variabilis populations(p﹤0.05). According to the UPGMA phylogenetic tree, 7 O. variabilis populations can be divided into three lineages.The genetic distance among Xiamen lineage and other two lineages reached 0.086-0.098. Maybe they were different subspecies.5 pairs of AFLP primers were used to investigate the genetic variation in O. variabilis. A total of 344 loci were detected from 5 populations. The proportion of polymorphic loci ranged from 40.5% to 56.42%. The genetic diatance were from 0.0189 to 0.1761. The result of cluster analysis was the same as the mitochondrial DNA analysis.The nucleotide composition of 9 species in Octopus based on 16S rRNA gene were studied and phylogenetic relationships among closely related species were generally well resolved combining with the sequences of other Cephalopod downloaded from Genbank.. The phylogenies supported that Octopus is not monophyletic.