欧氏和玛氏对盲囊线虫线粒体nad1基因部分序列的比较研究

欧氏对盲囊线虫(Contracaecum ogmorhini)和玛氏对盲囊线虫(Contracaecum margolisi)是属于欧氏对盲囊线虫复合种中的两个种，前来自于南半球，后来自于北半球，二在地理分布和宿主特异性方面均有明显的不同。本研究用γ^33P对引物进行标记，通过聚合酶链式反应一单链构象多态性(PCR—SSCP)分析和DNA序列分析技术对来自南半球两个不同地理种群的欧氏对盲囊线虫和北半球种群的玛氏对盲囊线虫在线粒体NADH脱氢酶亚单位Ⅰ基因(nad1)部分序列的差异及种群遗传关系进行了研究。结果显示：南半球两个种群的序列相似性很高，而北半球种群与南半球种群的序列相似性则相对较低，它们之间had1部分序列种间遗传差异大于种内，且存在着2个可作为区分两的遗传标记。种群遗传关系分析也表明：北半球的玛氏对盲囊线虫种群作为一个独立的新种而区别于南半球的两个欧氏对盲囊线虫种群。

Comparative studies on the mitochondrial nad1 gene sequences between Contracaecum ogmorhini and Contracaecum margolisi

Nucleotide difference in a portion of the mitochondrial NADH dehydrogenase subunit 1 (nad1) was studied among three populations of C.ogmorhini and C.margolisi from different otariid hosts and geographical, namely, one C.ogmorhini population from Arctocephalus pusillus pusillus (CoAPP) from South Africa, another from Arctocephalus pusillus doriferus (CoAPD) from Australia, and one C.margolisi population from Zalophus californianus (CoZC) from Pacific Canada. A nad1 fragment of approximately 500 bp in length was amplified from individual nematodes by PCR using ()~(33)P-endlabelled primers, analysed by single-strand conformation polymorphism (SSCP), and samples displaying variable SSCP profiles were subjected to sequencing. The results showed that the nucleotide similarity between CoZC and CoAPP/CoAPD was lower than that between CoAPP and CoAPD. Two genetic markers were defined for the differentiation between CoZC and CoAPP/CoAPD. The genetic analysis also confirmed that C.margolisi from the northern hemisphere represents a new species which differs from two populations of C.ogmorhini from the southern hemisphere.