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

本研究的目的是从形态学和分子生物学的角度阐明日本Meyersia japonica在田边湾两个潮下带（京都大学濑户海洋生物研究所北岸和薄竹岛南岸海岸）分离的两个种群的差异。1999年，在原产地采集了日本Meyersiajaponica个体，建立了RAPD分析方法。2000年，对该物种进行了广泛的调查，最终在不为人知的地方发现了Meyersia japonica的种群。2000年8月在这两个地点进行了取样。使用该材料，分析了身体形状的形态，例如尾长和气孔中的齿。为了进行分析，使用数码相机记录光学显微镜图像，并使用图像分析程序进行测量。因此，在所有测量项目中，未发现两个人群之间存在统计学显著差异。RAPD分析共使用了19个引物，其中5个引物扩增出2条以上的条带。共检测到33条多态性带，但仅有1. 13%为居群间变异，未观察到显著的遗传差异。这些结果表明，虽然该动物的扩散能力很小，但在地理上隔离的两个种群之间存在着基因流。虽然台风似乎在这种遗传流中扮演了重要的角色，但由于研究期间没有台风靠近田边湾，因此无法研究其影响。

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.