Freshwater Biodiversity in the countries surrounding the Japan Sea.

日本海在一万年前从一个淡水湖变成了大海。这可能会将湖中的生物分成日本和其他面向大海的国家。因此，预计它们在不同国家之间以不同的方式发展，对生物分布的调查有助于我们了解淡水生物多样性是如何发展的。在本研究项目中，我们试图进行调查。甲壳动物属的动物分布在各种水体、淡水湖、黑色湖泊和海洋中。我们发现一些物种在日本和韩国不同的生境中生存：例如，生活在日本淡水水体中的G.naktongense只在韩国的咸水湖泊中采集到，而在日本黑色湖泊中常见的G.chinense在韩国几乎没有发现。在对韩国淡水枝角类的调查中，从韩国采集的28种中有3种是日本没有的物种。对采自日本海周边国家的Pungitius属淡水鱼的同工酶分析表明，这些国家采集的淡水型伤寒沙门氏菌属于一个遗传群，而已知属于一个遗传群的淡水型动物分为两个群。这些结果表明，有必要重新考虑该鱼在东亚的分布。

The Japan Sea was changed from a freshwater lake to a sea ca. 10,000 years ago. This might separate the organisms in the lake into Japan and other countries facing the sea. It is expected, therefore, that they have developed in different ways between the countries, and that investigations on the distribution of the organisms help us with understanding how the freshwater biodiversity has been developed. In the present research project, we attempted to perform the investigations.Animals of the crustacean genus, Gnorimosphaeroma, are distributed in various water bodies, freshwater lakes, blackish lakes and sea. We have found that some species survive in different habitats between Japan and Korea: e.g., G. naktongense, which inhabits freshwater bodies in Japan, have been collected only from brackish lakes in Korea, while G. chinense, which are common species in blackish lakes in Japan, have scarcely been found in the same environment in Korea.In the investigation on freshwater Cladocera, three out of 28 species we collected from Korea have been found to be the species absent from Japan. The way of Cladocera to be distributed in such countries are discussed.The isozyme analyzes of freshwater fish of the genus Pungitius collected from countries surrounding the Japan Sea have demonstrated that the blackish-typed animals of P. tymensis collected from the countries are in a genetic group, while that the freshwater-typed ones, which have been known to be in a genetic group, are divided into two groups. The results suggest that it is necessary to reconsider the distribution of the fish in East Asia.