Morphological Characteristics And Genetic Diversity Of Culter Alburnus In Songhua Lake

Songhua Lake,also known as Fengman Reservoir,is located in the middle and upper reaches of Songhua River and is an important freshwater fishery resource pool in China.Culter alburnus is one of the characteristic fish in Songhua Lake,which has high economic value.In recent years,environmental pollution,overfishing and construction of wading projects have caused habitat changes.The decline of culter alburnus resources is serious.It is urgent to carry out the evaluation of the existing wild culter alburnus germplasm resources,so as to realize the protection and utilization of its germplasm resources.Based on the traditional morphology and mitochondrial DNA(mt DNA)COI gene sequence analysis,this paper introduced the population samples of culter alburnus in typical waters of southern China,including five major freshwater lakes,namely,Huaihe River,Yangtze River,the Taihu Lake,Gehu Lake and Dianshan Lake.At the same time,this study preliminarily discussed the genetic diversity of four culters populations in the Songhua Lake area and the close relationship between species.The specific research results are as follows:1.Traditional morphometrics were used to evaluate the morphological differences of Songhua Lake populations,and 14 indicators of Huaihe River,Taihu Lake and Dianshan Lake were used for multivariate statistical analysis to compare and analyze the morphological differences of Culter alburnu among the four geographical groups.Univariate analysis of variance showed that there were significant differences in SNL/BL、HL/BL、OD/BL、PVL/BL(P < 0.01).Principal component analysis showed that five principal components were extracted,and the contribution rates were 17.27%,14.18%,11.80%,7.86% and 7.35%,respectively.The cumulative contribution rate was 58.46%.The difference was mainly in the head and trunk;The results of Culter alburnu analysis showed that the four groups could be divided into two branches.The Huaihe river and Taihu lake populations were the most similar in morphology,and the Songhua and Dianshan Lakes were the first to converge into one branch.Stepwise discriminant analysis method was used to analyze the proportion of quantitative character data of four populations.The discriminant accuracy ranged from 69.23 to 96.08%,and the comprehensive discriminant rate was 78.06%.The discriminant accuracy of each population was in descending order: Songhua Lake,Dianshan Lake,Huaihe river and Taihu lake.The results showed that there were morphological differences among different populations,which could be distinguished effectively by multivariate analysis parameters.Different habitats and adaptation may be the main causes of morphological differences in Culter alburnus.2.In order to further evaluate the germplasm resources of Culter alburnus in Songhua Lake population,168 samples were collected from 44 Songhua Lake populations,30 Huaihe River populations,32 Yangtze River populations,31 the Taihu Lake Lake populations and 31 Gehu Lake populations.Based on the molecular genetic marker method of partial sequence of mt DNA COI gene,the genetic diversity of Culter alburnus population in Songhua Lake was evaluated.In the 526 bp COI gene sequence of Culter alburnus,the average content of base T,C,A and G was 25.3%,18.1%,28.1% and 28.6%,showing an AT bias;A total of 115 polymorphic loci were detected in 5 populations,and11 haplotypes were defined.The nucleotide diversity of the five populations ranged from0.00053 to 0.01834,and the haplotype diversity ranged from 0.280 to 0.746.The results show that the order of genetic diversity is Taihu Lake,Songhua Lake,Huaihe River,Yangtze River,and Gehu Lake.The genetic differentiation coefficient(Fst)and genetic distance analysis showed that there was significant genetic differentiation between Songhua Lake population and other populations,and the genetic distance was far from other populations.Analysis of molecular variance(AMOVA)showed that the genetic variation within populations was higher than that between populations(83.10% >16.90%).Neutral detection,mismatch distribution and Bayesian Skyline Plot(BSP)analysis showed that no population expansion occurred recently,and the population was relatively stable.The research results provide basic data for the protection and breeding of the genetic diversity of Culter alburnus.3.The genetic characteristics and genetic relationships of Culters in Songhua Lake were investigated.The genetic diversity of 139 types of Culters in Songhua Lake was investigated by using mt DNA COI gene sequences.The results showed that the base composition of the four species of hercules was similar.A total of 125 variant loci and 79 reduced information loci were detected in the 664 bp COI sequence.The average contents of base T,C,A and G were 27.47%,25.26%,28.29% and 18.48%,respectively.Base composition was biased,and the content of A+T(56.26%)was higher than that of C+G(43.74%).A total of 17 haplotypes were identified from four species of culters.The haplotype diversity ranged from 0.549 to 0.8756,and the nucleotide diversity ranged from0.00325 to 0.01467,with average nucleotide differences ranging from 2.159 to 9.743.Genetic diversity is as follows: Chanodichthys erythropterus,Culter alburnus,Culter mongolicus,Culter dabryi,The genetic structure showed that kimura’s 2-parameter was used to calculate the genetic distance of four species.The interspecific genetic distance ranged from 0.0474 to 0.0601,and Culter alburnus distance between and Chanodichthys erythropterus was the most distant.The intraspecific genetic distance ranged from 0.0033 to 0.0155,with Chanodichthys erythropterus having a greater genetic distance.The analysis of molecular variance showed that interpopulation variation was the main source of variation,accounting for 83.92% of genetic variation.The phylogenetic tree and haplotype network diagram showed that the 17 haplotypes were clustered in different species,and the different species were isolated from each other.The historical dynamic results showed that the Culter dabryi and Culter alburnus was significantly deviated from the neutral balance,and the mismatch distribution was unimodal,suggesting that the population had undergone enlargement.While,the mismatch distribution of Culter mongolicus and Chanodichthys erythropterus showed multi-peak and stable population.Overall,the genetic diversity of four species of culters in Songhua Lake was higher than that of culters.To sum up,this paper uses traditional morphological methods to compare and analyze the morphological differences of Culter alburnus in Songhua Lake population,and evaluates the morphological differences of Culter alburnus in Songhua Lake population from a macro perspective.According to the characteristic parameters,it can effectively identify the population of Culter alburnus in Songhua Lake,and provide data;The genetic diversity of Culter alburnus and other culters was further evaluated by combining the microscopic molecular markers of mt DNA COI gene.The results showed that the genetic diversity of Songhua Lake was relatively rich.Follow-up research can use morphological framework method and more molecular marker methods to comprehensively and systematically evaluate the germplasm resources and provide data reference for the protection and management of Culter alburnus in Songhua Lake.