| Collichtys lucidus(Perciformes,Sciaenidae,Collichthys)is widely distributed in China coastal area,particularly in the Yellow Sea and East China Sea.It is a short distance migratory species that inhabits warm sea water.As an important economic species,the number of C.lucidus in the market is very limited,which can't meet the market demand.Therefore,it is very important to study the genetic diversity of C.lucidus.In this study,we investigated the genetic characteristics,genetic diversity,and population difference of C.lucidus from seven geographical regions,via mitochondrial molecular marker techniques and multiple analysis methods such as traditional karyotype analysis,cluster analysis,principal component analysis and discriminant analysis.Results of this research may enhance our understanding of the status of offshore fish resources and provide considerable value for the genetic structure of the Sciaenidae species.Meanwhile it provides scientific data for the germplasm identification,effective management and sustainable utilization of C.lucidus.The main results are as follows:1.Karyotype analysis of C.lucidusFishes used for karyotype analysis were taken from Ningde coast of China.The metaphase chromosomes of C.lucidus were obtained from kidney tissue by PHA and colchicine injection-air drying method.In order to identify whether there were heteromorphic chromosomes,we separated the female from the male.The female was separated from the male to identify heteromorphic chromosomes.The results showed that there were48 chromosomes in C.lucidus and its karyotype formula was 2n=48t,NF=48.The relative lengths of chromosomes were in the range of 5.69 to3.03,suggesting the karyotype of C.lucidus was in accordance with the original karyotype of the perciformes and the higher group of fish evolutionary taxonomy.Moreover,sex chromosome,satellite chromosome and secondary constrictions were not found in C.lucidus.However,further research was needed to make sure whether there were sex chromosomes.This study was beneficial to the identification,protection and utilization of the germplasm resources of C.lucidus,as well as the cross breeding of the fish of sciaenidae,laying foundations for the construction of genetic map,gene localization and so on.2.Morphological variations of 7 C.lucidus geographical populationsIn this study,morphological comparative studies were performed in238 C.lucidus individuals,which were collected from 7 different geographic areas including Lian Yungang,Dafeng,Chongming,Zhoushan,Ningde,Xiamen and Wenzhou.Furthermore,One-Way ANOVA analysis,principle component analysis,cluster analysis and discriminant analysis were used to analyze 13 morphological traits and 20 truss network characters of these populations..Because the differences of individual size could affect the results,all data were calibrated by their body length(BL).One way ANOVA analysis showed that there were significant differences between the 7 C.lucidus geographical populations.The four principal components which were identified by principal component analysis have accounted for 53.131%,9.328%,4.249%,and 3.406% respectively in differences among 7 populations,so their contributed to population differences over 70% in total.The principal component 1 reflected the characteristics of the trunk(body depth/BL,D6/BL,D7/BL,D8/BL,D9/BL,D11/BL and D14/BL),indicating that these characteristics can be used as the basis for judging population differences.Both clusters analysis and principle component analysis showed that there was no obvious north-south differentiation in the morphology of 7 C.lucidus geographical population.Based on discrimination analysis,the comprehensive discrimination rate of the 7 C.lucidus geographical populations was 85.3%,and discriminant accuracy ratio was 62.5%-96.7% for P1,and 78.1%-90.6% for P2.The discrimination accuracy of Zhoushan population was low because of its unique geographical factors,including ocean current and freshwater flow.This study provides basic morphological data for geographical population identification,germplasm resources protection as well as selective breeding of C.lucidus.3.Population genetic structure analysis of C.lucidus based on D-loop geneTo evaluate the population structure of C.lucidus,the genetic variation of mitochondrial DNA D-loop region among these 7 wild populations were analyzed.By using PCR amplification and sequencing,795 bp of D-loop sequences were obtained and conformed to the base preference characteristics.A total of 83 haplotypes and 66 variable sites were detected from 208 C.lucidus individuals.The haplotype diversity and nucleotide diversity of the 7 populations were ranged from(0.554 +0.00998)to(0.954 + 0.00067)and 0.00183 to 0.00708,respectively.The Fst value of the total populations was 0.86647(P=0),and genetic distance between every two populations ranged from 0.004 to 0.039.Fst,genetic distance,haplotype adjacency tree and haplotype network all showed that C.lucidus has obvious geographic genetic structure,divided into northern(Lianyungang,Chongming,Dafeng and Zhoushan group)and South groups(Wenzhou,Ningde and Xiamen group).The neutrality test(Tajima's D,Fu's Fs)and mismatch distribution analysis both implicated that all 7 C.lucidus populations might have experienced either a directional selection or an expansion in population size.Our results might provide basic data for the protection and reasonable utilization of C.lucidus. |
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