2004 Fiscal Year Final Research Report Summary
Analyses on Species Diversity on Parasitic Helminths based on Molecular Phylogeny
| Project/Area Number |
14596008
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生物多様性・分類
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| Research Institution | National Science Museum, Tokyo |
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Principal Investigator |
KURAMOCHI Toshiaki National Science Museum, Tokyo, Department of Zoology, Senior Curator, 動物研究部, 主任研究官 (80277590)
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| Project Period (FY) |
2002 – 2004
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| Keywords | parasitic helminths / species diversity / Nematoda / Pseudaliidae / mitochondrial DNA / COI / molecular phylogeny / Phocoenidae |
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| Research Abstract |
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
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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
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