Comparative Study On The Morphology And Genetics Of The Released Population Of Squid Mansoni And The Wild Population

The Sepiella japonica,belong to order Cephalopoda,family Decapoda,genus Sepiidae.In this study,the genetic structure and genetic diversity of five artificial releasing populations and two wild populations were compared and analyzed by traditional morphological analysis,mitochondrial DNA and microsatellite molecular markers.The artificial releasing populations were breed in Xixuan island of zhoushan,and the wild populations were captured from Zhoushan offshore.Morphological analysis: Five artificial releasing S.japonica populations and two wild populations were statistically analyzed that use the traditional morphological method.Ten indicators were included,such as cuttle length,cuttle width,total length,head length,manthe length,manth width,eye distance,eye diameter,withrs heigth,manthe length/manth width.The results showed that there were significant differences between two wild populations(YS1 and YS2)and five artificial releasing populations(F,F1,F2,F3 and F4)on the five morphological indexes of cuttle length,cuttle width,manthe length,head length and cuttle length,cuttle width.This indicates that there were some morphological differences between wild and artificial releasing populations.The morphological differences between the five artificial releasing populations were small.Microsatellite primer isolation and characterization: Next-generation sequencing and de novo assembly were used for potential useful microsatellite markers obtaining of S.japonica.25 primer pairs showed polymorphism among S.japonica individuals,number of alleles,observed and expected heterozygosity per locus ranged from 2 to 8,0.083 to 0.922 and 0.042 to 0.866,respectively.The PIC ranged from 0.04 to 0.829.Microsatellite analysis: Genetic diversity of two wild and five artificial releasing S.japonica populations were studied by using six microsatellite loci markers.The results showed that the average alleles of the lowest was F3,with a value of 6.167.The highest average alleles was YS1,with a value of 11.The lowest observed heterozygosity was F3,with a value of 0.396.The highest average observed heterozygosity was YS1,with a value of 0.535.The lowest average expected heterozygosity was F3,with a value of 0.675.The highest average expected heterozygosity was YS1,with a value of 0.779.The lowest average PIC was F3,with a value of 0.588.The highest average PIC was YS1,with a value of 0.737.The lowest average Shannon index was F2,with a value of 1.401.The highest average Shannon index was F3,with a value of 1.869.The level of genetic diversity of two wild S.japonica populations were slightly higher than that five artificial S.japonica populations.Mitochondrial DNA analysis: Mitochondrial COI gene was used to study the genetic diversity of two wild and five artificial releasing S.japonica populations.The results showed that,two wild S.japonica populations were higher than five artificial releasing S.japonica populations in haplotype diversity,nucleotide diversity and polymorphic site.When adding a out population to F1,the genetic diversity of F2 was improved.NJ phylogenetic tree showed that there were no obvious branches among haplotypes,and haplotype H2 was abundant in 7 populations.This study speculated that haplotype H2 mainly comes from the artificial releasing population,so it is abundant in the natural sea.