Studies on speciation of Asian schistosomes

迄今为止，亚洲血吸虫的系统发育尚不清楚。本研究采用PCR技术对日本血吸虫、米孔血吸虫和马来西亚血吸虫三种亚洲血吸虫进行了分子系统发育分析。扩增细胞色素C氧化酶I亚基（COI）片段，并将其克隆到ta载体上。采用ABI测序仪/染料引物法。共测序395个碱基对，并采用Paup （Maximum Parsimony Method）和cluster V （The Neighbor-Joining Method）进行分析。作为外群，使用了两个非洲种，S.mansoni和S.haematobium。两种方法构建了相同的系统发育树。也就是说，m. kongi和m. malaynsis首先聚集在一起，然后与S.japonicum合并。将这两个非洲种与亚洲种结合成一个簇，并进行了染色体的c带模式分析，该模式显示了S.mekongi和S.malaynsis之间更密切的关系，支持了本研究得到的分子系统发育树。对三种寄主螺（Robertsiella gismani, Neotricula aperta, Oncomelania nosophora）进行了核型分析。结果发现，吉斯马尼Robertsiella gismani和新三角藻（Neotricula aperta）的性染色体数目均为2n=34，但性染色体似乎分别为XY型和XO型。在嗜黑钉螺的情况下，没有发生性染色体分化。同时进行了感染实验。选用日本钉螺3只，分别为钉螺、小钉螺和日本血吸虫。结果发现，只有医院钉螺对日本血吸虫和马来西亚血吸虫感染敏感。

Phylogeny among Asian Schistosoma flukes have not been known so far. In the present study, PCR technique was used to make up a molecular phylogeny on three Asian Schistosoma species, S.japonicum, S.mekongi, and S.malaynsis. A region of cytochrome C oxidase subunit I (COI) was amplified, and the fragment was cloned into TA-vector. The ABI sequencer/the Dye primer method were used. In total, 395 base pairs were sequenced, and analyzed with Paup (Maximum Parsimony Method) and Clustal V (The Neighbor-Joining Method). As outgroups, two African species, S.mansoni and S.haematobium were used. Both of the two methods constructed the same phylogenetic trees. That is, S.mekongi and S.malaynsis was clustered first, and joined with S.japonicum. The two African species were joined into a cluster, and bound with the Asian species.C-banding pattern analysis of the chromosomes was also performed The pattern showed closer relationships between S.mekongi and S.malaynsis, supporting the molecular phylogenetic tree obtained in this study. Karyotypic analysis of the snail host species, Robertsiella gismani, Neotricula aperta, and Oncomelania nosophora were carried out. It was found that chromosome numbers were all 2n=34, but sex chromosomes seem to be of XY type and XO type for Robertsiella gismani and Neotricula aperta, respectively. In the case of Oncomelania nosophora, no sex chromosome differenciation occurred.Infection experiments were also carried out. Three Japanese snails, Oncomelania nosophora, O.minima and Bythinella nipponica were used. It was found that only Oncomelania nosophora was susceptible to S.japonicum and S.malaynsis infection.