GENETIC POLLUTION AND DISTURBANCE OF SYMBIOTIC SYSTEM OF THE FRESHWATER SHRIMP, NEOCARIDINA DENTICULATA DENTUCULATA, BY THE INVASION OF CLOSELY RELATED ALIEN SPECIES

分类学上悬而未决的对虾Necaridina spp.的入侵。从中国进入日本一直被怀疑通过进口作为诱饵。为了澄清这一怀疑，我们收集了来自日本和中国的对虾及其共生体并进行了分析。根据线粒体DNA CO I和16SrRNA基因的部分序列，发现了两个主要的单倍型分支。分支I由仅在日本发现的单倍型组成，而分支II由从两个国家观察到的单倍型组成。分支II包括日本和中国的核苷酸相同或几乎不同的单倍型。这表明，分支I和分支II分别归属于日本本土谱系(即齿纹网纹夜蛾)和中国的外来谱系。这些事实表明，新卡里丁藻属的入侵。从中国进入日本的事情确实发生了。在日本的四个地方，这两个分支被共存，暗示着本土种群和外来种群之间通过杂交或渗入而造成的遗传污染。结合对虾出口商和进口商的听证调查，异种新卡氏藻属。据推测是从中国的北部和中部引进的，而共生的Brchiobdellidan H.truncatus是最近在日本中部从中国的中部记录的。

Recent invasion of taxonomically unsettled atyid shrimp Neocaridina spp. from China into Japan has been suspected through the import as fishing bait. To elucidate this suspicion, the shrimps and their symbionts were collected and analyzed both from Japan and China. Two major haplotype clades were found for Neocaridina spp., based on the sequenced partial CO I and 16SrRNA genes of the mtDNA. Clade I was composed of the haplotypes detected only from Japan, while Clade II was composed of those observed from both countries. Clade II included the haplotypes with identical or few nucleotide differences between Japan and China. This indicates that Clades I and II are assigned to the indigenous lineage in Japan (i.e., N.denticulata denticulata) and the exotic ones from China, respectively. These facts suggest that invasion of Neocaridina spp. from China into Japan has really occurred. In four localities of Japan, the two clades were observed sympatrically, implying the genetic pollution through hybridization or introgression between indigenous and exotic populations. Together with the hearing investigation from exporters and importers of the shrimps, exotic Neocaridina spp. were supposed to have been introduced from the northern and middle part of China, and the symbiotic branchiobdellidan, H. truncatus, recently recorded in central Japan from the middle part of China.