Population structure and recruitment mechanism of Conger myriaster larvae using otolith microsturucture and mitochondrial DNA sequences

根据1996年和1998年在宫崎县野冈县、熊本县矢津县、香川县阿治县、静冈县清水县和福岛县索马县采集的细头鲸矢状耳石的生长增量，研究了长尾鲸的生长历史和繁殖情况。所有标本均在变质带前识别出深检。本研究将该标记称为“滨前标记”，该标记可作为研究该物种生长历史和补充机制的基准标记。耳石检查表明，幼虫在119.5日龄时已进入沿岸水域，110-210日龄发生变态。孵化日期从9月延长到1月。采用线粒体DNA序列测定了16只毛囊细头绦虫控制区前半部分细胞色素b基因的一部分，以评价该物种的种群结构。从宫崎县Nobeoka、熊本县Yatsushiro和福岛县Soma的16个标本中，共测序了591个核苷酸位点，其中细胞色素b基因位于控制区前半部分。在对照区396个核苷酸位点中，发现31个（7.8%）可变，16个单倍型。核苷酸序列之间的差异在0.25 ~ 4.55%之间，平均为1.88%，表明该物种线粒体DNA控制区具有高变异性的特点。用邻接法构建的系统发育树没有显示出明显的地理聚类。这一结果表明，目前的标本可能来自一个单一的种群。

The growth history and recruitment of Conger myriaster were studied, based on growth increments in sagittal otoliths of leptocephali collected from Nobeoka (Miyazaki Pref.), Yatsushiro (Kumamoto Pref.), Aji (Kagawa Pref.), Shimizu (Shizuoka Pref.) and Soma (Fukushima Pref.) in 1996 and in 1998. The deep check was recognized at before metamorphic zone from all specimen. The check was called the "Coastal front mark" in the present study and this mark may be useful as a bench mark in studying the growth history and recruitment mechanism of the species. Examination of otoliths showed that larvae has entered into coastal water at the age of 119.5 days, and metamorphosis occurred at 110-210 days. Hatching dates extended from September to January.Mitochondrial DNA sequences that include a part of the cytochrome b gene to the first half of the control region of 16 C.myriaster leptocephali were determined to evaluate the population structure of the species. A total of 591 nucleotide site, including cytochrome b gene to the first half of the control region, was sequenced from 16 specimens from Nobeoka (Miyazaki Pref.), Yatsushiro (Kumamoto Pref.) and Soma (Fukushima Pref.). Out of 396 nucleotide sites on the control region, 31 (7.8 %) variable, 16 haplotypes being found. Differences between nucleotide sequences ranged between 0.25 and 4.55% with average of 1.88 %, indicating that the control region of the mitochondrial DNA in the species is characterized be high variability. The phylogenetic tree constructed by the neighbor-joining method shows neither significant geographic clusters. This result indicate that the present specimen might come from a single population.