College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, People's Republic of China.
Parasitol Res. 2010 Aug;107(3):547-53. doi: 10.1007/s00436-010-1891-1. Epub 2010 May 8.
This study investigated the genetic variability within fish louse Argulus japonicus (Crustacea: Branchiura) from Africa, Middle East, and Asia by polymerase chain reaction in three mitochondrial DNA (mtDNA) regions, namely, cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunits 1 and 4 (nad1 and nad4). Six different sequences from a portion of the cox1 gene (pcox1) and a portion of the nad1 and nad4 genes (pnad1 and pnad4) for ten adult specimens from infected fish in China, Egypt, and Syria were amplified separately from individual and the amplicons were subjected to direct sequencing. A + T percentages were 68.8-69% for pcox1, 77.1-77.6% for pnad1, and 60.4-60.9% for pnad4. Among all the collected parasites, A. japonicus sequence variations were 0.0-1.9% for cox1, 0.0-2.3% for nad1, and 0.0-0.8% for nad4. In rivers, sequence variations among all individuals were 0.4-0.8% for cox1, 1.0-2.3% for nad1, and 0.4-0.8% for nad4, while sequence variations among all the collected parasites in fish farms were 0.6-1.9% for cox1, 0.0-1.7% for nad1, and 0.2-0.6% for nad4. The nad1 was the most variable gene among selected markers, while nad4 was a more conserved gene than cox1. All isolates of A. japonicus were sister to Argulus americanus in phylogenetic tree and they grouped together in one sub-clade, while isolates from China and Egypt fish farms were closely clustered together. However, moderate genetic drift and slight mutation could be observed among A. japonicus individuals. These findings demonstrated the convenience and attributes of the three selected mtDNA sequences for population genetic studies of A. japonicus where nad1 is a new and reliable marker to detect the sequence variation among A. japonicus individuals.
本研究通过聚合酶链反应（PCR）在三个线粒体 DNA（mtDNA）区域（细胞色素 c 氧化酶亚基 1（cox1）和 NADH 脱氢酶亚基 1 和 4（nad1 和 nad4））中研究了来自非洲、中东和亚洲的鱼虱 Argulus japonicus 的遗传变异性。从中国、埃及和叙利亚受感染鱼类的 10 个成年标本的 cox1 基因的一部分（pcox1）和 nad1 和 nad4 基因的一部分（pnad1 和 pnad4）中分别扩增了六个不同的序列，将扩增子分别进行个体扩增，然后直接测序。pcox1 的 A+T 百分比为 68.8-69%，pnad1 为 77.1-77.6%，pnad4 为 60.4-60.9%。在所收集的寄生虫中，cox1 的 A. japonicus 序列变异为 0.0-1.9%，nad1 为 0.0-2.3%，nad4 为 0.0-0.8%。在河流中，所有个体的 cox1 序列变异为 0.4-0.8%，nad1 为 1.0-2.3%，nad4 为 0.4-0.8%，而在鱼类养殖场中所有寄生虫的序列变异为 cox1 为 0.6-1.9%，nad1 为 0.0-1.7%，nad4 为 0.2-0.6%。所选标记中，nad1 是最具变异性的基因，而 nad4 比 cox1 更保守。Argulus japonicus 的所有分离株与 Argulus americanus 在系统发育树中为姐妹关系，它们聚集在一个亚分支中，而来自中国和埃及养殖场的分离株则紧密聚集在一起。然而，在 Argulus japonicus 个体中可以观察到适度的遗传漂移和轻微的突变。这些发现证明了所选三个 mtDNA 序列在 Argulus japonicus 种群遗传研究中的便利性和特性，其中 nad1 是检测 Argulus japonicus 个体之间序列变异的新的可靠标记。
