Study On Morphological And Genetic Comparison Of Sardinella Zunasi Populations

Primary morphological characters were measured and the data were analyzed by principle component analysis method, multivariate analysis method and ANOVA to study the morphological variations among four populations of Sardinella zunasi in China and Japan. The results showed that: some morphological characters had significant differences and there were geographical differences in the distributions of S. zunasi. According to Mayr's 75% rule, the differences among the four populations of S. zunasi were still within the population level, not in the subspecies level.Six hundred and twenty six base pairs (bp) of the partial mitochondrial control region from 77 (S. zunasi) collected from China (Qingdao population and Zhoushan population) and Japan (Aichi population and Kagawa population) were sequenced.The phylogeographic characteristics and genetic population structure were investigated. Sixty nine haplotypes were determined and only one haplotype was shared between Aichi population and Kagawa population. The haplotype frequencies showed that genetic diversity of Qingdao population was the highest, and Zhoushan population was lower than other populations. Analysis of Molecular Variance(AMOVA)indicated the differences between two different populations were very significant. Neighbor-joining tree for control region haplotypes of S. zunasi showed there were three lineages of haplotypes (A, B and C), and the mismatch distributions revealed three lineages experienced sudden population expansion. Molecular tree constructed by NJ method showed the individuals of the different populations couldn't be clustered as one independent group and mixed to each other.The mitochondrial cytochrome b gene fragment (402bp) of four Sardinella species were amplified and sequenced with the method of PCR, and the differences of sequences were analyzed. Nine haplotypes were observed in ten samples. The average contents of T,C,A,G were 28.9%,28.2%,23.9%,19.0% respectively and the content of A+T was higher than that of G+C which was similar to the sequences of other fishes. With the Kimura 2-parameter model we got the genetic distances was between 0.1616 and 0.2653. Based on sequences of partial cytochrome b gene, a phylogenetic tree was constructed by NJ method and the results indicated the S. zunasi and S. jussieui, S. maderensis and S. aurita had a relatively close relationship, respectively. Molecular evolution rate showed the divergence of four Sardinella species occurred during the middle and late Miocene about 800 and 1300 million years ago. The results showed the divergence time was earlier than most fishes, and Sardinella species were in a relatively low level of evolution.Mitochondrial cytochrome oxidase subunit I (COI) fragments of S. aurita and S. zunasi were amplified. A total sequence of 599 nucleotide base pair was obtained by alignment with homologous sequences of another two Sardinella species in GenBank. There were 445 parsimony-informative sites and 154 variation sites, but no insertion/deletions were observed. By sequencing, the average base compositions were 28.4%, 28.7%, 22.5% and 20.3% for T, C, A and G respectively. Base G content was much lower than the others. The Amino acid sequences of four Sardinella species were totally the same. The genetic distance among the four Sardinella species ranged from 0.158 to 0.205. The NJ phylogenetic tree of four Sardinella species showed that S. melanura and S. jussieui, S. zunasi and S. aurita had close genetic relationship between respectively.