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

本研究旨在从形态学和分子生物学的角度，阐明在田边湾两个潮下地区，即京都大学濑户海洋生物实验室北岸和畑岛南岸建立的两个海洋线虫（Meyersia japonica）分离种群的差异。1999年，我们在原址采集了稻叶螟个体，建立了RAPD分析方法。但在高竹岛未发现该物种的种群。因此，在2000年，对该物种进行了广泛的调查，最终在未知的地方发现了日本稻叶螟种群。2000年8月在两个地点进行了抽样。利用该材料，分析了体形形态学，如尾长和齿在造口。为了进行分析，使用数码相机记录光学显微图像，并使用图像分析程序进行测量。结果，两个人群在所有测量项目中没有发现统计学上的显著差异。在分子RAPD分析中，共使用了19条引物，其中5条引物具有2个以上条带。共检测到33个多态性条带，但群体间变异率仅为1.13%，遗传差异不显著。这些结果表明，尽管这种动物几乎没有传播能力，但在两个地理上隔离的日本稻叶螟种群之间存在基因流动。虽然台风似乎对这一遗传流起了重要作用，但由于在研究期间没有台风接近田边湾，我们无法研究其影响。

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.