Analyses on Species Diversity on Parasitic Helminths based on Molecular Phylogeny

寄生蠕虫的多样性机制进行了分析，重点是家庭的伪aliidae（线虫纲），这广泛的寄生在小鲸类主要是家庭的Phocoenidae。日本周围沃茨分布有三种伪线虫，即达尔氏鼠海豚Phocoenoides dalli、江豚Noephocaena phocaenoides和港湾鼠海豚Phocoena phocoena，其中达尔氏鼠海豚Phocoenaphocoena分别寄生有五种伪线虫，港湾鼠海豚Phocoenaphocoena也寄生有几种伪线虫。本研究从寄主的生殖发育角度出发，探讨了在三种不同的生境条件下，小球藻的物种形成过程。例如，利用线粒体DNA编码的细胞色素c氧化酶亚单位I（COI）基因约1.2kbps的部分序列进行分析。用于分析的线虫是来自达尔氏鼠海豚的两属五种， ...更多信息 江豚2属1种。相邻树分析表明，这些拟海鲶科鱼类可分为两个类群，一个类群包括来自达尔氏鼠海豚的Parurus dalli、Stenurus truei和S.yamagutii，以及来自江豚的Pseudostenurus sunameri;另一个类群由来自海港鼠海豚的S.minor和来自达尔氏鼠海豚和江豚的盐尾藻属的3个种组成。传统上，狭尾属、Pharurus属和Pseudostenurus属被归为狭尾亚科，主要寄生于颅窦和鼻腔，而盐尾属也使盐尾亚科寄生于肺支气管。因此，这是一个非常意外的结果。根据这些结果，提出了几个物种形成过程，其中，将拟银汉鱼科分为两个类群的演化过程是在拟银汉鱼从拟银汉鱼科祖先演化而来时通过协同进化而形成的，盐尾虫属的共同祖先是由小盐尾虫等颅窦居群通过向支气管迁移而进化而来的，其后代则在其他的盐尾虫类中出没; 3种拟海豚类共域分布于达尔氏鼠海豚的颅窦内，但生殖隔离的机制尚不清楚;将宿主从达尔氏鼠海豚换成江豚。少

Mechanisms of diversification on parasitic helminths were analyzes focusing on the family Pseudaliidae (Nematoda), which widely infest in the small cetaceans mainly from the family Phocoenidae. In the waters around Japan three members of the phocoenids distribute, Dall's porpoise Phocoenoides dalli, finless porpoise Noephocaena phocaenoides and harbour porpoise Phocoena phocoena, of which the former two are parasitized by five species of pseudaliid nematodes each and the latter is also infested by several species of the same family. In this study, the processes of speciation were investigated, considering the host's phylogeny, under three categolies i. e., co-evolution, host exchange and sympatric speciation by using molecular based analyses.The partial sequences of about 1.2 kbps from cytochrome c oxidase sub-unit I (COI) gene encoded on mitochondrial DNA (mDNA) were used for analyses. The nematodes used for analyses were five species of two genera from Dall's porpoise, two species of … More two genera from finless porpoise and one species from harbor porpoise. The neighbor-joining tree indicated that these pseudaliids were divided into two clusters, one contained Parurus dalli, Stenurus truei and S.yamagutii derived from Dall's porpoise, and Pseudostenurus sunameri from finless porpoise; and the other was constructed by S.minor from harbour porpoise and surprisingly three species of the genus Halocercus from Dall's porpoise and finless porpoise. Conventionally, the genus Stenurus, Pharurus and Pseudostenurus are classified into the subfamily Stenurinae mainly inhabit in the cranial sinus and nasal cavity, while the genus Halocercus also makes the subfamily Halocercinae parasitic in the bronchi of lung. Thus, this is a quite unexpected result. On the other hand, P.sunameri from finless porspose was closely related with S.truei from Dall's porpoise.So far these results are concerned, several processes of speciation are suggested, the clusters dividing the family Pseudaliidae into two was made by co-evolution when harbour porpose was derived from the phocoenid ancestor, the common ancestor of the genus Halocercus was derived from the cranial sinus inhabitants such like S.minor by changing their habitat to the bronchi, and the descendants infested in other phocoenids; three species of pseudaliids inhabit in the cranial sinus of Dall's porpoise speciated sympatrically, although the mechanism of the reproductive isolation is unknown ; P.sunameri occurred from S. truei by changing a host from Dall's porpoise to finless porpoise. Less