Study on physiology and ecology of Gambierdiscus occurred in deep water (> 10 m depth) in order to clarify a mechanism of ciguatera outbreaks in Japan

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H04535
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Kochi University
• Principal Investigator: Adachi Masao 高知大学, 教育研究部自然科学系農学部門, 教授 (70274363)
• Co-Investigator(Kenkyū-buntansha): 大西 浩平 高知大学, 教育研究部総合科学系生命環境医学部門, 教授 (50211800)
• Research Collaborator: Tanaka Koki ; Yanagida Ippei
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: シガテラ / 有毒渦鞭毛藻 / 地球温暖化

Outline of Final Research Achievements

Toxic dinoflagellates genus Gambierdiscus are the causative agents of ciguatera fish poisoning. It has been analyzed that occurrences and cell densities of Gambierdiscus species in shallow waters of Japanese coastal areas. However, those in deeper waters has not been analyzed yet. This study assessed the occurrences in the deeper waters (> 10 m depth). A strain of Gambierdiscus was isolated from a deep water (30 m depth). The strain was identified as G. silvae based on the morphological features as well as the phylogenetic position. The strain showed mouse toxicities. The optimal temperature, salinity, and light intensity for G. silvae was 25°C, 30 PSU, and 115 micromol photons/m2/s. It was clarified that the species distributed from shallow waters to deep waters in the areas by using qPCR assay. Finally, using meta-analysis based on 18S rDNA V8/V9 sequences, Gambierdiscus species including G. silvae as well as a novel clade/species were found in the Japanese coastal areas.

Free Research Field

海洋環境微生物学

Academic Significance and Societal Importance of the Research Achievements

本研究では、これまで未検討であった本邦沿岸における水深10～30 m層に存在するシガテラ原因藻Gambierdiscus属に注目し、太平洋からは初報告となるGambierdiscus silvaeを見出した。さらに、本種の生理・生態を解明し、本種が本邦におけるシガテラ発生に深く関与している可能性を指摘した。また、本研究では次世代シーケンサーを活用することにより、本邦沿岸域にて発生するGambierdiscus属の群集組成を網羅的に明らかにすることに成功し、これまでに報告の無い新奇種を見出した。本研究により得られた結果は、沿岸魚類の毒化予察やシガテラへの対策法の策定にも役立つものと期待される。