Laboratori d'Ictiologia Genètica, Departament de Biologia, Universitat de Girona, Girona, Spain.
PLoS One. 2009 Oct 27;4(10):e7606. doi: 10.1371/journal.pone.0007606.
Tuna species of the genus Thunnus, such as the bluefin tunas, are some of the most important and yet most endangered trade fish in the world. Identification of these species in traded forms, however, may be difficult depending on the presentation of the products, which may hamper conservation efforts on trade control. In this paper, we validated a genetic methodology that can fully distinguish between the eight Thunnus species from any kind of processed tissue.
After testing several genetic markers, a complete discrimination of the eight tuna species was achieved using Forensically Informative Nucleotide Sequencing based primarily on the sequence variability of the hypervariable genetic marker mitochondrial DNA control region (mtDNA CR), followed, in some specific cases, by a second validation by a nuclear marker rDNA first internal transcribed spacer (ITS1). This methodology was able to distinguish all tuna species, including those belonging to the subgenus Neothunnus that are very closely related, and in consequence can not be differentiated with other genetic markers of lower variability. This methodology also took into consideration the presence of introgression that has been reported in past studies between T. thynnus, T. orientalis and T. alalunga. Finally, we applied the methodology to cross-check the species identity of 26 processed tuna samples.
Using the combination of two genetic markers, one mitochondrial and another nuclear, allows a full discrimination between all eight tuna species. Unexpectedly, the genetic marker traditionally used for DNA barcoding, cytochrome oxidase 1, could not differentiate all species, thus its use as a genetic marker for tuna species identification is questioned.
金枪鱼属的金枪鱼物种，如蓝鳍金枪鱼，是世界上最重要但最濒危的贸易鱼类之一。然而，根据产品的呈现方式，这些物种在交易形式中的鉴定可能很困难，这可能会阻碍贸易控制方面的保护工作。在本文中，我们验证了一种遗传方法，该方法可以从任何加工组织中完全区分八种金枪鱼物种。
在测试了几种遗传标记物之后，通过基于线粒体 DNA 控制区（mtDNA CR）序列变异性的法医信息核苷酸测序，主要实现了对这八种金枪鱼物种的完全区分，在某些特定情况下，通过核标记 rDNA 第一内部转录间隔区（ITS1）进行第二次验证。该方法能够区分所有金枪鱼物种，包括那些属于近缘亚种 Neothunnus 的物种，因此不能用其他变异性较低的遗传标记物来区分。该方法还考虑了过去研究中报告的在 T. thynnus、T. orientalis 和 T. alalunga 之间存在的基因渐渗现象。最后，我们应用该方法对 26 个加工金枪鱼样本的物种身份进行了交叉检查。
使用两种遗传标记物（一种线粒体标记物和另一种核标记物）可完全区分所有八种金枪鱼物种。出人意料的是，传统上用于 DNA 条形码的遗传标记物细胞色素氧化酶 1 无法区分所有物种，因此其作为金枪鱼物种鉴定的遗传标记物的用途受到质疑。
