以粒線體DNA標記建立西北太平洋長鰭鮪之族群結構

Abstract

長鰭鮪(Thunnus alalunga)，俗名白肉串，為一高度洄游之魚種，主要分布於太平洋，大西洋，印度洋45°N與50°S間之熱帶及溫帶海域，適水溫域為13.5°C與25.2°C之間，為高經濟價值魚種，亦為世界漁業之主要漁獲對象，因此該魚種族群結構與來源之探索及瞭解，將有助於其資源之評估、管理與利用。本研究利用粒線體基因標記之生物技術方法，鑑定西北太平洋長鰭鮪之族群結構，並探討其親緣關係。本研究採集了西北太平洋三個採樣區（台灣、日本、夏威夷）之長鰭鮪肌肉樣本，萃取其粒線體DNA (mtDNA)，利用特定引子(primer)，針對mtDNA全段控制區約860個鹼基對，以PCR反應，將mtDNA控制區放大並定序，成功得到共175個長鰭鮪mtDNA控制區序列。所得控制區序列以Clustal X軟體逕行分析比對，隨後，將此不同的單倍基因型以Kimura 2-Parameter model方法建構所的長鰭鮪但被基因型之親緣關係樹。NJ樹形的可信度以1000次重複的bootstrap法進行統計檢測。結果顯示：親緣關係樹可將西北太平洋海域三個採樣區之長鰭鮪分為兩個clades: Clade I包含多數(98%)之長鰭鮪單倍基因型; Clade II則包含相當少量(2%)之長鰭鮪單倍基因型。另外，Clade I內又分為兩支lineages: Lineage I及Lineage II。AMOVA與F-statistics分析結果顯示西北太平洋長鰭鮪族群之族群遺傳結構分化情況並不顯著，即西北太平洋內為單一系群，且三海域之長鰭鮪兼有基因交流的現象。

Albacore (Thunnus alalunga) is a highly migratory cosmopolitan fish commonly distributed throughout tropical, subtropical and temperate areas of all oceans including the Mediterranean Sea. Due to its commercial and economic importance, a better understanding of its genetic structure is essential to an effective fishery management. In the current study, population structure of albacore in the Northwestern Pacific Ocean was investigated using mitochondrial DNA control region (D-loop) sequence data specifically of the first hypervariable region (HVR-1). A total of 175 individuals were caught and sampled from three regions in the Northwestern Pacific Ocean (Taiwan, Japan and Hawaii). Total DNA of each sample was isolated and purified. With the use of specific primers, the entire mtDNA control region was amplified through Polymerase Chain Reaction. The mtDNA were aligned using ClustalX and 168 haplotypes were revealed. Neighbor-joining tree based on the Kimura 2-parameters model was constructed using MEGA with 1000 bootstrap replicates. The reconstructed neighbor-joining phylogeny tree based on sequencing data of these 175 samples suggested that albacore haplotypes in these three sampling regions can be divided into two main clades (Clade I and Clade II) with one clade (Clade I) further sub-divided into two lineages (Lineage I and Lineage II). Hierarchical AMOVA tests and pairwise FST analysis showed that albacore tuna in the Northwestern Pacific Ocean constituted a single stock with no significant differences in geographic distributions.