yrammuS 要概鏡味麻衣子東京湾における赤潮原因珪藻の真の消費者を探る79Maiko KAGAMI佐藤 拓哉80Takuya SATO（2019採択）Exploring the real consumers of bloom forming diatoms in Tokyo Bay(Project 2019)生息地の分断が引き起こす種内多様性の急速な消失：サケ科魚類の降海関連DNA変異による検証（2019採択）The effect of habitat fragmentation on the variation of migration-related genes in red-spotted masu salmon(Project 2019)63administration via artificial diet to larvae. These results indicate that the pale grass blue butterfly has been af-fected by the initial direct exposure and by indirect field effects mediated by the host plant.東京湾では珪藻が大発生する赤潮現象が起こるが，その消失過程は未だ明らかになっていない．本研究では，東京湾の赤潮形成珪藻を消費しうる真核微生物に焦点を当て，その多様性を把握し，珪藻との関係を明らかにすることを目的とした．調査，顕微鏡観察，単離培養実験， DNA解析を併用した結果，東京湾には珪藻を捕食する多様な真核微生物（アメーバ，鞭毛虫，菌類）が存在することが明らかとなった．とくにアメーバや鞭毛虫は種類によって捕食できる珪藻（宿主特異性）や生息可能温度に違いがあり，出現時期が異なることも明らかとなった．いずれの種類も赤潮の原因となる珪藻Skeletonema属を好んで捕食すること，その摂食速度が大きいことから，時期を変えて多様な真核微生物が出現することで，珪藻の動態に影響を与えていると推察された．In Tokyo Bay, red tides occur frequently, caused mainly by diatoms, yet it is still not clear how the red tides disappear. In this study, we focused on the eukaryotic microorganisms which may consume the red tide form-ing diatoms, and examined their diversity and relationships with diatoms. Combining field surveys, micro-scopic observations, isolation, culture experiments and DNA analysis, we successfully revealed diverse eu-karyotic microorganisms, such as amoebae, flagellates and fungi, feeding on diatoms in Tokyo Bay. They were highly host specific, feeding on different diatom species, and survived at different temperatures, which may have caused different seasonal patterns. Since all of them could consume the red tide forming diatom, Skeletonema, with high feeding rates, suggesting that the appearance of various eukaryotic microorganisms at different time of the year must have influenced the dynamics of diatoms and red tides.種内多様性は，種の多様性よりもはるかに速いスピードで失われており，その有効な保全は生物多様性保全における急務である．今日，地球規模で進む生息地の分断は，多くの動物の生息地間移動（＝移住）を妨げ，移住に関わるDNA変異を消失させることで，種の存続を脅かしている可能性がある．本研究では，種内の移住多型であるサツキマス（降海型）とアマゴ（河川残留型）に注目して，ダムや砂防堰堤による生息地の分断が，降海型に関わる遺伝子型の変異を失わせている可能性を見出した．Rapid loss of intra-specific variation is a central issue in conservation biology. To date, habitat fragmentations have caused massive decline in migratory animals and plants worldwide, which may result in rapid loss of migratory-related genetic variations and ultimately species extinctions. In this study, we tested whether the habitat fragementation by damming caused loss of migratory-related genetic variation in Oncorhynchus masou ishikawae, a partially-migratory salmonid species.Rep. Grant. Res., Asahi Glass Foundation (2022)
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