Investigation of the distribution and host range of the flagellate causing soft tunic syndrome of sea pineapple.

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K06208
• 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: Yamaguchi University
• Principal Investigator: Yanagida Tetsuya 山口大学, 共同獣医学部, 准教授 (40431837)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 被嚢軟化症 / ホヤ / 鞭毛虫

Outline of Final Research Achievements

In this study, the distribution and host range of the flagellate Azumiobodo hoyamushi, the causative agent of the soft tunic syndrome (STS) of an edible ascidian Halocynthia roretzi, was investigated. About 500 ascidians including H. roretzi were collected from 15 regions where STS has never been reported, and none of them were infected with A. hoyamushi. The result suggests that A. hoyamushi only distributed along the coastal areas of Tohoku region, where STS has been reported in the ascidian aquaculture. On the other hand, evolutionary closely related flagellates were detected from ascidians collected in this study, indicating the possibility of existence of the unknown flagellates parasitic to ascidians.

Free Research Field

寄生虫学

Academic Significance and Societal Importance of the Research Achievements

本研究により、ホヤムシの分布域はマボヤ養殖で被嚢軟化症が発生している東北地方沿岸に現局している可能性が示された。マボヤ自体は本研究で調査した瀬戸内海等にも分布しているため、本研究の結果は、ホヤムシがもともと国内に存在したのではなく、海外から移入したという従来の仮説を支持するものといえる。また、ホヤムシはホヤ類の被嚢に寄生することが知られている唯一の鞭毛虫だが、本研究により、ホヤムシがホヤ類に寄生するに至った進化的な経緯を解明する道が開けた。