Genetic Population Genetic Variation Of Oratosquilla Oratoria In Eastern Coastal Waters Of China

Oratosquilla oratoria belongs to the family Squilidae, widely distributed in the Bohai Sea, Yellow Sea and East China Sea. It is an important marine economic crustacean in the coastal waters of China.In the present study, morphological and mitochondrial DNA were used to study the genetic diversity of O.oratoria in the East China Sea and Yellow Sea of China. To discuss the taxonomic status of O.oratoria in the East China Sea and Yellow Sea group, two mtDNA genes were also used to analyze the phylogenetic relationship of six mantis shrimps.Morphological variation among five geographic populations(Tangshan, Dongying,Qingdao, Lianyungang and Zhoushan) of O.oratoria was studied using one way-ANOVA analysis, cluster analysis, principal component analysis and discriminant analysis. The results of one way-ANOVA analysis showed some differences among five geographic populations, but it was not significant. Cluster analysis revealed that there was no apparent clustering related to the geographical locations. The principal component analysis resulted in two principal components, the contributory ratios of the two principal components were60.540% and 20.795%, respectively. The cumulative contributory ratio was 81.335%. The discriminant analysis revealed that the discriminant accuracy of Zhoushan population was the highest(75.6%) and Lianyungang was the lowest(41.9%), the average discriminant accuracy was 65.4%. Morphological study showed that there were no significant morphological differences between populations in the East China Sea and Yellow Sea, but it's not clear. We cannot distinguish the East China Sea group and Yellow Sea group through morphological characteristics.To examine population genetic differentiation between the East China Sea and Yellow Sea population of O.oratoria, two mtDNA gene sequences were used to analysis population genetic structure.(1) a 525-bp fragment of the 16 S rRNA gene was sequenced in this species. In total, 124 individuals were collected from seven locations(Tangshan,Dongying, Qingdao, Lianyungang, Xiaoyangshan island, Zhoushan and Qixing archipelago) in the East China Sea and Yellow Sea, 31 haplotypes were obtained. Mean haplotype diversity and nucleotide diversity were 0.8193±0.0272 and 0.0036±0.0022respectively; Haplotype network and NJ tree identified two distinct lineages, the divergence time of lineages A and B was about 566,000 years before present; Significant genetic variation were found by AMOVA analysis and pairwise FST(FST=-0.0361-0.6560);Mismatch distribution and neutrality test revealed that O.oratoria had undergone population expansion.(2) a 658-bp fragment of the COI gene was sequenced in this species.In total, 211 individuals were collected from nine locations(Tangshan, Dongying,Longkou, Qingdao, Lianyungang, Xiaoyangshan island, Zhoushan Sanmen and Qixing archipelago) in the East China Sea and Yellow Sea, 108 haplotypes were obtained, mean haplotype diversity and nucleotide diversity were 0.9731±0.0054 and 0.0320±0.0156 respectively, population genetic diversity was in a high level; haplotype network and NJ tree complete genetic break between the East China Sea and Yellow Sea; significant genetic variation were found by AMOVA analysis and pairwise FST; mismatch distribution and neutrality test revealed that O. oratoria had undergone population expansion.The results of two mtDNA gene sequences revealed that higher levels of population genetic diversity were found in the East China Sea and Yellow Sea populations; Distinct lineages between two groups belongs to different geographical populations. Significant genetic variation were found by AMOVA analysis and pairwise FST; The Yangtze River outflow as a physical barrier might limit the gene connectivity between two groups.Besides the Yangtze River outflow,the water temperature between the East China Sea and Yellow Sea also has an effect on the genetic differentiation of O.oratoria.To further analyze the taxomomic status of O.oratoria, two molecular markers were used to analyse the phylogenetic relationship of six mantis shrimps from the family Squilidae. The results of the two mtDNA gene sequences were following: the smallest net genetic distance between two geographical populations of O.oratoria were 0.056(COI) and0.004(16S rRNA) respectively. The smallest net genetic distance between six mantis shrimps was found in O.oratoria and Miyakea nepa, the net genetic distance were0.112(COI) and 0.020(16S rRNA) respectively. The conclusion was that the net genetic distance between two groups only reach to the population or subspecies, it has not reach the level of species. To further study the classification of two geographical populations, we need to use nuclear gene and morphological analysis to confirm the taxonomic status of O.oratoria in two groups.