Genetic Diversity Comparison Of Coilia Brachygnathus And Neosalanx Taihuensis Between Populations In The Three Gorges Reservoir And Dongting Lake

Coilia brachygnathus and Neosalanx taihuensis are both of commercial important edemic fishes in China.In recent years,due to environmental pollution,overfishing and hydraulic construction,the natural stock resources of these two fishes declined,and the genetic diversitieswere reduced.After the completion of the Three Gorges Dam,the aquaticecological environment of the Three Gorges Reservoir was changed in the upper reaches of the Yangtze River.C.brachygnathus and N.taihuensis gradually formed a certain scale of population in the upperstream.For the better understanding of the population genetic diversity and providing basic data to their resource protection and management of these two types of fish in the Three Gorges Reservoir.In this study,24 C.brachygnathus samples were collected from Three Gorges Reservoir and Dongting Lake respectively,as well as 25 and 70 N.taihuensis samples from Three Gorges Reservoir and Dongting Lake,morphological and molecular biological methods were used to compare the morphological characteristics of two fish populations in the Three Gorges Reservoir and Dongting Lake.The complete mitochondrial genome of C.brachygnathus form the Three Gorges Reservoir(TGR)was sequenced and analyzed.The genetic diversity of between two N.taihuensis populations was compared using the combination of 12 sRNA,16 sRNA,CO ?,ND1 gene sequences of mitochondrial genome.1.Toidentify coilia fish from TGR,using morphylogical and measurement character to identified as C.brachygnathus based on Yuan Chuanmi classification criterion,Morphological analysis of two C.brachygnathus populations of 16 six of traits existed differences.there were five principal components in the TGR population,four principal components in Dongting Lake population by the principal componentanalysis,which indicated that age structure showed that two populations became lower in age,the Dongting Lake population more lower than the TGR population,2-year age individuals accounted for 56.7% inTGR group and 1-year age individuals accounted for60.0% in the Dongting Lake population.2.The total mitochondrial genome sequence length of C.brachygnathus in the TGR was 16,865,including 13 coding proteins,22 tRNA,2 rRNA and a D-loop sequence,which was similar to that of C.brachygnathus in the Dongting lake,only with17 different bases,accounting for only 0.33%.3.The genetic diversity of C.brachygnathus between the two populations based on the D-loop sequence of mitochondrial genome was compared.The total of 16 sites of variation(S)were detected in 48 C.brachygnathus samples.The total number of mutations was 22.The total of 19 different haploids were detected.Haploid type diversity(Hd)was 0.883±0.037,nucleotide diversity(?)0.00523,and the average number of nucleotide differences(K)2.771.There were 9 population variation loci(S)in the TGR population,the mutation total number 7,and the nucleotide multiplicity(?)0.00444.There were 6 population variation loci(S)in the Dongting Lake population,the mutation total number 7,and the nucleotide multiplicity(?)is 00017.The genetic distance between the two populations was 0.00454.4.The genetic diversity of N.taihuensis between the two populations based on the combination of 12 sRNA,16sRNA,CO?,ND1 gene sequence of mitochondrial genome.Among 95 N.taihuensis samples(Five of the 100 icefishe samples were Hemisalanx brachyrostralis),there were 36 mutation sites(S)and 37 mutations in total.A total of 18 different haplotypes were detected,with a haplotype diversity(Hd)of 0.558±0.058,a nucleotide diversity(?)of 0.00060 and an average nucleotide difference number(K)of1.409.There were 24 haplotypes,24 variation heterosites(S),59 mutations in total,haplotype diversity 0.730,nucleotide diversity(?)0.0013 and average nucleotide difference was 3.158 in Dongting Lake population.In the TGR population,haplotype number of population was 3,variation locus(S)3,total number of mutations 2,haplotype diversity 0.075,nucleotide diversity(?)0.00023 and average nucleotide difference was0.533.The genetic distance between the two populations was 0.0049.In conclusion,the presentstudy first reported the Coilia fish population in the TGR of upstream of the Yangtze River.Using morphology and mitochondrial genome sequence analysis identified it's the Coilia fish as C.brachygnathus.The genetic diversity analysis of the mitochondrial D-Loop sequence of C.brachygnathus samplesform the TGR and Dongting Lake found that genetic distance of two populations was close,which suggested that the TGR population is likely to derived fromthe downstream population The genetic diversity and genetic distance of N.taihuensis beteewen the Dongting Lake population and the TGR were compared and analyzed by using the combination of 4 mitochondrial gene sequences.The results showed that the genetic distance of two populations were closely related.The results suggested that after the completion of the TGR,the habitats of fishes changed tremendously,which has been resulting in the fish community structure towards "lakes" development,and the impact of the dam construction on the TGR aquaticecosystem begins toemerge.