Genetic population structure and ecophysiological differentiation of Japanese flounder

本研究对采自北海道、高知、三重、韩国南部和中国青岛附近的日本比目鱼线粒体DNA控制区进行了序列分析。Fujii和Nishida（1997）对包括佐渡岛在内的所有数据进行的主要2个单倍型组成和Fst值分析表明，分布在日本各地的日本比目鱼具有同质的遗传结构，尽管只有佐渡岛与其他岛屿之间存在轻微但显着的差异。在中国人群中观察到不同的单倍型组成。另一方面，从韩国南部收集的比目鱼显示出几乎相同的碱基排列，它们应该是被丢弃的孵化场饲养的幼鱼。饲养实验进行了冷水适应的北方群体和温暖适应的南方群体之间的生态生理特性的差异。从岩手县的宫古和熊本县的阿马库萨将受精的比目鱼卵运送到京都大学渔业站，并使用封闭循环水族箱在14、18和22℃的水温下从孵化到变态完成饲养幼虫。在18℃下饲养的早期幼鱼，分别转入10、14、18、22、26、30℃ 6个温度区，饲养至50mm SL。这些饲养试验表明，北方群体在低温下比南方群体具有更高的生长潜力，由此可以得出结论，即使在具有同质遗传结构的情况下，日本鲽地方群体也具有不同的生理特性，以适应区域环境。

Analyses on sequence of mtDNA control region were conducted for Japanese flounder collected in Hokkaido, Kochi, Mie, southern Korea and near Qingdau, China. Composition of major 2 haplotypes and Fst value analyses for all data previously published including Sado Island analyzed by Fujii and Nishida (1997) demonstrated homogeneous genetic structure in the Japanese flounder distributed around Japan although slight but significant difference was only found between Sado Island and the others. A different haplotype composition was observed in Chinese population. On the other hand, the flounder collected from southern Korea showed almost same base alignment, and they were supposed to be discarded hatchery-raised juveniles.Rearing experiments were done to see differences in eco-physiological characteristics between cold-water adapted northern population and warm-adapted southern population. Fertilized flounder eggs were transported from Miyako, Iwate and from Amakusa, Kumamoto to the Fisheries Station of Kyoto University, and the larvae were reared from hatching through completion of metamorphosis at water temperatures 14, 18, and 22℃ using closed circulating aquaria. Early juveniles reared at 18℃ were transferred to 6 temperature regimes 10, 14, 18, 22, 26, 30℃ and reared until 50mm SL. These rearing experiments suggested that northern population has higher growth potential than southern population under lower temperatures.Based on these data we could conclude that Japanese flounder local population has different physiological characteristics adapted to regional environments even when they demonstrate a homogeneous genetic structure.