Studies Of Morphological Characteristics And Genetic Diversity On Populations Of Small Yellow Croaker(Larimichthys Polyactis) And The Difference Between Small Yellow Croaker And Large Yellow Croaker (Larimichthys Crocea)

Small yellow croaker (Larimichthys polyactis) and large yellow croaker(Larimichthys crocea), which belong to Perciformes, Percoidei, Sciaendae,Larimichthys, are both warm temperate demersal fish and important economicalspecies in China. The small yellow croaker are mainly distributed in the Bohai Sea,Yellow Sea and East China Sea; large yellow croaker are mainly distributed insouthern Yellow Sea, East China Sea and South China Sea. In this study, we usetraditional morphological markers, otolith morphological markers and microsatellitemarkers to analysis the genetic structure and diversity among the differentgeographical populations of small yellow croaker and the relationship between smallyellow croaker and large yellow croaker.We compare the morphological difference among nine small yellow croakerpopulations collected from Bohai Sea, Yellow Sea and East China Sea based on20morphological characteristics and8meristic counts. The meristic counts areconsistent with the previous taxonomic information. The range of meristic counts areapproximate same in different pupulations, so it can’t be the factor to judgment. Theresult of principal component analysis, discriminant analysis and one-way ANOVAshows that there are significant genetic differences among different populations.We use shape index and Fourier analysis to research the otolith morphologybased on8shape index and77Fourier value. The result of one-way ANOVA,principal component analysis and discriminant analysis shows that there aresignificant genetic differences among different populations, but no distinct geneticdifferentiation among different seas. Seven pairs of microsatellite primers are used to analyze10populations of thesmall yellow croaker. The number of alleles are12to47in7loci, the averageobserved heterozygosity are0.60to0.74. The PIC are0.40to0.95, all but one loci(LYC0018) are high polymorphic loci. There have a high level genetic variation andrich genetic diversity in small yellow croaker. The Fst value obtained from theanalysis of molecular variance (AMOVA) in10populations is only0.0049. Thegenetic differentiation between small yellow croaker is very weak. We obtain smallFst, from0.0010to0.0303. The significant Fst are mainly in North Yellow Sea andSouth Yellow Sea, South Yellow Sea and East China Sea. We didn’t finddifferentiation between East China Sea group and the Bohai group.We compare the difference between small yellow croaker and large yellowcroaker based on traditional morphological characteristic, otolith and microsatellite.Using principal component analysis, discriminant analysis and cluster analysis toanalyze morphological difference between large yellow croaker and small yellowcroaker. Two species have significant difference, especially in the number of vertebrae.Large yellow croaker have26vertebra, small yellow croaker is27to29. This twospecies have thick oval otolith, without rostrum, antirostrum, postrostrum andpararostrum. The difference of the otolith between two species is visible, large yellowcroaker otolith back end is more pointed, small yellow croaker is more obtuse. Theventral side of otolith in small yellow croaker is smooth, but it has a significantconcavity in large yellow croaker. Principal component analysis, discriminant analysisand cluster analysis demonstrate that otolith can distinguish this two fish well.Microsatellite analysis indicate that two species have a high level of diversity, the Fstvalue between species is0.08. The divergence between two species occurred about123000years before present in Late Pleistocene based on genetic distance.