2021 Fiscal Year Final Research Report

Why does the red tide of Heterocapsa kill only shellfish?

Research Project

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Project/Area Number	18K05809
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 40030:Aquatic bioproduction science-related
Research Institution	Fisheries Research and Education Agency
Principal Investigator	Yamasaki Yasuhiro 国立研究開発法人水産研究・教育機構, 水産大学校, 講師 (40598471)
Co-Investigator(Kenkyū-buntansha)	紫加田知幸国立研究開発法人水産研究・教育機構, 水産技術研究所(廿日市), 主任研究員 (40603048) 内山郁夫基礎生物学研究所, ゲノム情報研究室, 准教授 (90243089)
Project Period (FY)	2018-04-01 – 2022-03-31
Keywords	赤潮 / ヘテロカプサ / 溶血活性 / トランスクリプトーム / 二枚貝へい死 / シオミズツボワムシ
Outline of Final Research Achievements	Heterocapsa circularisquama is a harmful red tide-causing dinoflagellate that is extremely toxic to shellfish. In this study, we compared and analyzed the gene expression level of this species between strains with different toxicity or between different culture conditions. As a result of enrichment analysis of a highly virulent strain and an attenuated strain selected by the hemolysis test and the toxicity test using the rotifer Brachionus plicatilis, the photosynthesis-related genes were characteristically highly expressed in the highly virulent strain as compared with the attenuated strain. On the other hand, when the highly toxic strain of this species was cultured in a nitrogen or phosphorus-deficient medium, a clear decrease in photosynthetic activity and toxicity to <i>B. plicatilis<i> was observed after the 5th day of culture. Therefore, our results suggest that activation of photosynthesis is necessary for the development of toxicity.
Free Research Field	水圏生産科学
Academic Significance and Societal Importance of the Research Achievements	本種の溶血活性やシオミズツボワムシ（以下，ワムシ）に対する毒性がアサリに対する毒性と一致したことから，簡易毒性試験は現場に出現した本種の毒性リスク評価に有効であると考えられる。特に，ワムシの曝露試験は低密度（10 cells/mL）でも本種の毒性を検出できることから，赤潮による漁業被害の軽減技術のひとつとして本種法の社会実装が期待される。また，本研究では本種の毒性と光合成活性に相関関係を見出したことから，光合成活性についても現場に出現した本種の毒性リスク評価に応用できる可能性がある。