光裸方格星虫野生与养殖群体线粒体控制区序列的遗传差异分析

基于线粒体控制区序列对光裸方格星虫（Sipunculus nudus Linnaeus，1766）的2个养殖群体（营盘YP、竹林ZL）和4个野生群体（防城港FC、钦州QZ、大冠沙DG和越南海防YN）的91个个体进行遗传差异分析，研究光裸方格星虫养殖和野生群体的遗传变异情况。结果显示:获得的514 bp DNA序列中，野生与养殖群体的多态性位点数分别为82和60，均显示出对AT的偏倚性。共定义85个单倍型，共享单倍型4个，其中共享单倍型Hap5为原始单倍型，营盘群体均为独享单倍型。各群体的单倍型多样性（H_d）相同，野生群体的平均核苷酸多样性（P_i）（0.01531）略高于养殖群体（0.01514），6个群体的遗传多样性水平依次为YN > YP > QZ > FC > ZL > DG。各群体间的遗传分化并不显著（P>0.05），光裸方格星虫的遗传变异主要来自群体内个体间（99.08%），同时未发现明显的地理谱系结构。研究表明，光裸方格星虫野生群体的遗传多样性水平总体略高于养殖群体；滩涂底播养殖方式较池塘养殖更利于维持光裸方格星虫遗传多样性；各群体间不存在显著的遗传分化，养殖群体正逐渐积累遗传变异，但尚未足够以形成其独立的遗传结构。

GENETIC VARIATION ANALYSIS ON WILD AND CULTURED POPULATIONS OF SIPUNCULUS NUDUS INFERRED FROM MTDNA CONTROL REGION SEQUENCES

Sipunculus nudus is one of the commercially important inshore demersal species. Understanding the popula-tion genetic of this species is a critical component of conservation management and artificial reproduction. However, few studies were reported about the genetic variation between wild and cultured population. The current study em-ployed ninety-one mitochondrial DNA control region sequences to analyze the genetic variation of two cultured (Ying-pan and Zhulin in Beihai) and four wild (Daguansha, Qinzhou, Fangchenggang in China and Haiphong in Vietnam) populations of S. nudus. Results showed that sixty and eighty-two polymorphic sites were detected in cultured and wild populations based on the 514 bp sequence, respectively. A negative GC-skew was found in mtDNA control region se-quences of S. nudus. Eighty-five haplotypes were identified from control region sequences, among which 4 haplotypes were shared by all populations except Yingpan. According to the Median-joining network, the Hap5 was the chief an-cestral haplotype of S. nudus. The average nucleotide diversity (Pi) (0.01514) of cultured populations was slightly lower than the wild populations (0.01531), and all populations had the same haplotype diversity (Hd). The order of genetic di-versity for six populations was: YN>YP>QZ>FC>ZL>DG. No significant (P>0.05) genetic differentiations were detec-ted among populations in terms of the genetic distance and fixation index (Fst). The AMOVA analysis indicated that the genetic variance mainly appeared within populations (99.08%). Non-significant genealogical structures were found from NJ and Median-joining network analyses among populations. The genetic diversity of wild population was slightly higher than the cultured populations. The bottom sowing culture was more beneficial to maintain high level ge-netic diversity of S. nudus. Meanwhile, the genetic differentiations existed among populations were not significant, and the cultured population accumulated genetic variations try to form its own genetic structure.