Studies On Morphological Characteristics And Genetic Diversity Of Commercial Fishes From South-west Atlantic

Samples were commercial fishes collected on board “Lurongyu No.6177andNo.6178” operating in the Southwest Atlantic Ocean off Argentina during January2011to April2011.In this study, traditional morphological markers andMitochondrial DNA molecular markers were used to analysis the genetic diversityamong the samples.Firstly, a total of71single individuals of14species were amplified for a652bpregion of mitochondrial cytochrome oxidase subunit I gene (COI). The GC content ofthe10species of teleost was higher than the4species of rays (46.9%versus43.1%).The average intra-species,-genus,-family, and-order of Kimura twoparameter (K2P) distances are0.0028,0.0335,0.1866and0.2361, respectively. In theneighbour-joining tree for28haplotypes of71COI sequences, the clades that speciesclustered generally corresponded well with the results of morphological classification.It is concluded that COI sequencing can be used to identify fish species effectively.And it can become a kind of supplement and revision for fish morphologicalclassification system.Secondly，we compared the morphological differences among four populationsof Argentina hake based on18meansurable character and8countable character, andthen we studied on genetics diversity among two of these populations based on thefirst hypervariable region (HVR-1) of the mitochondrial DNA control region. Thedistributions of values for ench countable character of Argentine hake populationswere familiar,so it couldn’t be a judgment factor. The result of principal componentanalysis, discriminant analysis showed that there were significant genetic differencesbetween the various groups.High levels of haplotype diversity in the HVR-1regionindicated a high level of genetic diversity.The study based on one-way ANOVAanalysis and Fst showed the presence of a certain degree of genetic differencesbetween two populations. Thirdly, traditional morphological analysis were performed among threepopulations of Argentine anchovy and two of them were analyzed genetic diversitybased on the HVR-1region. The traditional morphological analysis was based on18metric values and8subsection characteristics.The statistical analysis results ofprincipal component analysis and one-way ANOVA,etc,.indicated that the degree ofdifferentiation between the two populations was relatively low,and the differentiationswere still blong to the geographical differences. We amplified437bp HVR-1regionand detected26haplotypes.The haplotype diversity was0.968%and mean pairwisenucleotide difference was0.012%. According to the high haplotype diversity and lownucleotide difference,we inferred the populations experienced expansion events.Tajima’s D and Fu’s Fs test also supported this result.Fourthly，we studied on genetic differentiations of two Argentine shortfin squidpopulations by two molecular markers of mitochondrial cytochrome oxidase I (COI)and cytochrome b (Cytb) gene. Based on COI gene, the number of haplotype,haplotype diversity, nucleotide diversity and mean pairwise nucleotide differences are34、0.8692±0.0378、0.0068±0.0039、3.5915±1.8423. And based on Cytb gene, thesame values are31、0.9066±0.0244、0.0073±0.0042、3.0190±1.5913. The twomolecular markers both revealed that the two populations of I. argentines had a higherhaplotype diversety and a lower nucleotide diversity. And the Fst value and the N-Jtree both showed that the genetic differentiation of two populations was significantand there is a certain population genetic structure between them.