象山港养殖大黄鱼寄生新贝尼登虫成虫形态学和28S rDNA,ITS1分子鉴定

贝尼登类单殖吸虫是象山港海水养殖鱼类中一类危害严重的寄生虫。应用PCR扩增及DNA序列分析的分子生物学手段,并结合对成虫的形态学分析,对象山港养殖大黄鱼体表寄生的贝尼登类单殖吸虫(记作XSp)进行了种类鉴定,结果表明XSp从形态特征上属于新贝尼登虫属,与梅氏新贝尼登虫高度相似。扩增得到XSp的28S rDNA和ITS1序列长度分别为393和427 bp,与梅氏新贝尼登虫和鱾新贝尼登虫的5个28S rDNA 序列、2个ITS1序列的比对分析显示相似性除1个为97.4%外其余均大于99%,提示XSp与这几个鱾新贝尼登虫和梅氏新贝尼登虫为种内关系,而XSp与贝尼登虫的3个28S rDNA 和1个ITS1序列相似性分别为84.3%~89.5%和60.2%。系统进化树显示该吸虫与梅氏新贝尼登虫和鱾新贝尼登虫形成一个紧密的簇,而与贝尼登虫亲缘关系较远。根据普通生物学和序列特征分析,将XSp定种为梅氏新贝尼登虫,并且支持Whittington和Horton (1996)提出的梅氏新贝尼登虫和鱾新贝尼登虫为同种异名的分类观点。

28S rDNA, ITS1 and adults morphological identification of Neobenedenia in cultured Pseudosciaena crocea at Xiangshan Harbor

In recent years, Neobenedenia has caused serious damage on cage-cultured fish at Xiangshan Harbor, Zhejiang Province, China. The Neobenedenia adults (denoted by XSp) were collected from cultured Pseudosciaena crocea. The XSp sequences of 28S coding region of rRNA gene (28S rDNA) and the first internal transcribed spacer (ITS1) as well as morphology were studied for identification. The morphological characteristics showed that XSp belongs to Neobenedenia which was morphologically similar to Neobenedenia melleni. In XSp, the length of 28S rDNA was 393 bp and ITS1 was 427 bp. In phylogenetic analysis, Neobenedenia and Benedenia were split into two clades, and the XSp was in clade Neobenedenia. The sequences identities of 28S rDNA and ITS1 were 84.3%~89.5% and 60.2% among XSp and Benedenia, respectively. With one exception of 97.4%, the sequences identiteis of 28S rDNA and ITS1 among XSp, N. melleni and N. girellae were above 99%, which indicated that they are the same species. The results of two identification methods showed that the Neobenedenia at Xiangshan Harbor was N. melleni, and supported the opinion in which Whittington & Horton (1996) proposed that N. melleni and N. girellae were synonymy.