Movement and dispersal of marine nematodes living in the interstitial space of sand

本研究的目的是从形态和分子生物学的角度，阐明在田边湾滨海生物实验室北岸、京都大学和厦门岛南岸两个潮下带建立的两个独立的海洋线虫种群的差异。1999年，我们从原产地采集了日本小菜蛾个体，并建立了随机扩增多态性DNA分析方法。然而，在服谷岛没有发现该物种的种群。于是，在2000年，对该岛周围的物种进行了广泛的调查，最终从未知的地方发现了Meyersia Japan onica的种群。2000年8月在这两个地点进行了抽样。利用该材料分析了尾长、气孔内齿等体型的形态特征。为了进行分析，用数码相机记录了光镜图像，并用图像分析程序进行了测量。结果，在所有测量项目上，两个人群之间没有发现统计学上的显著差异。用19个引物进行分子扩增，其中5个引物扩增出2条以上条带。共检测到33条多态带，但只有1.13%是居群间变异的，没有明显的遗传差异。这些结果表明，虽然这种动物的扩散能力很小，但在两个地理上隔离的湄公河流域种群之间存在着基因流动。虽然台风似乎对这一成因流起到了重要作用，但我们无法研究其影响，因为在研究期间没有台风接近田边湾。

The purpose of the present study is to clarify the difference of isolated two population of marine nematodes Meyersia japonica population established at two subtidal areas in Tanabe Bay, i.e. north shore of the Seto Marine Biological Laboratory, Kyoto University and south shore of Hatake jima island, from the points of view of morphology and molecular biology. In 1999, Meyersia japonica individuals were collected from the former site, and we established method for RAPD analysis. However, population of the species in Hatake jima was not found. In 2000, thus, an extensive survey of the species was carried out around the island, and population of Meyersia japonica finally was found from unknown place. Sampling was done in August 2000 at both sites. Using the material, morphology of body shape, e.g. tail length and teeth in the stoma were analyzed. To do the analysis, light microscopic image was recorded using digital camera, and measurement was done using image analyzing program. As a result, no statistically significant difference was found between two populations in all measured items. For molecular RAPD analysis, 19 primers were used, and 5 of them had more than two bands. A total of 33 polymorphic bands were detected, but only 1.13 % of them were the variation among populations, and no significant genetic difference was observed. These results suggest that though the animal has little ability of dispersal, there is a flow of gene between two geographically isolated Meyersia japonica populations. Though typhoon seems to play an important role for this genetic flow, we could not study its affect because no typhoon approached to Tanabe Bay during the study period.