| Co-Investigator(Kenkyū-buntansha) |
HISHINUMA Tasuku Yamagata Univ., Facul.Sci., Lecturer, 理学部, 講師 (70181097)
JORDAN Richard Yamagata Univ., Facul.Sci., Ass.Prof., 理学部, 助教授 (90260455)
HANZAWA Naoto Yamagata Univ., Facul.Sci., Ass.Prof., 理学部, 助教授 (40292411)
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| Research Abstract |
In Palau Archipelago, about 80 marine lakes are located around Rocky Island District. These lakes are isolated from open sea and provide closed marine ecosystem to oceanic life systems. Almost all are geologically and genetically isolated from those inhabiting open seas, at least ten thousand years ago when the marine lakes were formed after he last glacial age. They show unique gross morphology, therefore it can be supposed that they have drifted on their own evolutionary processes. During our seven expeditions to Palau, 19 marine lakes have been accessed. On the limnological sense, these are divided into two of the holomictic and meromictic lakes. In the case of seaweeds in marine lakes, the similar species compositons and common dominant species share depending on these types of marine lakes. This is the center of this project for taking the evidences of their peculiar evolution of dominant or represenntative seaweeds and other groups of animal assembrages in the marine lakes based
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on the analyses of morphology and molecular phylogeny. The estimation of marine lakes' ages has been tried using the radio isotope and micropaleontological methods on the basis of sediments deposited in the bottom of lakes. Unfortunately, the suitable samples for these analyses could not be collected from all marine lakes we accessed. Consequently, we have to consider that the standard age of marine lakes in Palau is approxmately ten thoughsand years previously thought.
From the results obtained here, the identification system of seaweeds in marine lakes based on their external morphology and internal strucutres was established with the verification of the molecular phylogenetic analysis. Owing to use this system, we could compare the genetic divergences of seaweeds inside and outside, as well as inter and intra marine lakes. At present, we could not show the clear evidences to occur the peculiar evolution of marine life systems in marine lakes, however, the possibilities could be exhibit on animal assebrages using mitochondrial genomes. While the peculiar evolution of seaweeds was mostly neglected at 18SrDNA, rbcL and ITS region levels. Further investigations will be needed after introducing molecules with much more rapid evolutionary speed or another methods possessing the resolving power to much more closely phylogenetic relationships. Less
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