Is the mass mortality of pearl oyster in the summer of 2019 a Tenacibaculosis ?

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06203
• 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: University of Toyama
• Principal Investigator: SAKATOKU Akihiro 富山大学, 学術研究部理学系, 講師 (20713142)
• Co-Investigator(Kenkyū-buntansha): 一色 正 三重大学, 生物資源学研究科, 教授 (30378319)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 真珠 / アコヤガイ / 軟体部萎縮症 / 殻黒変病 / Vibrio sp. MA3株 / Tenacibaculum sp. Pbs-1株

Outline of Final Research Achievements

The purpose of this study that we describe the isolation and characterization of a pathogenic bacterium as a first step towards resolving the recent disease outbreaks in cultured pearl oysters, as characterized by extreme atrophy of their soft tissues. In addition, we develop a specific detection method for Tenacibaculum sp. Pbs-1 associated with black-spot shell disease in akoya pearl.
We isolated a Vibrio sp. strain MA3 from the mantle and other soft tissues of diseased pearl oysters. Strain MA3 possessed a pathogenic factor, hemolysin (Vhe1), of vibriosis. Moreover, the results of the infection-challenge experiment in this study provide evidence that strain MA3 was one of the putative causal agents of mass mortalities of farmed pearl oysters in Japan in the summers of 2019 and 2020. We developed and evaluated a rapid, specific, and sensitive loop mediated isothermal amplification assay to detect Tenacibaculum sp. Pbs-1 associated with black spot shell disease.

Free Research Field

環境微生物学

Academic Significance and Societal Importance of the Research Achievements

日本の養殖アコヤ真珠は, 世界的に非常に評価が高く, 日本の水産物年間輸出額の11% (約330億円) を超える重要な輸出産業となっている。しかし近年, 母貝の殻内側が著しく黒変し, 低品質の真珠形成や死亡を引き起こす‘殻黒変病’と, 外套膜が極端に委縮し死亡する‘軟体部萎縮症’が全国の真珠養殖場で大きな問題となっている。これらの疾病の全容解明は, 緊急性を要し, 日本が誇る真珠養殖産業の持続・発展に不可欠の課題である。本研究成果は, その解決に向けた第一歩であり, 学術的・社会的意義は高いと考えられる。