Rediscovery of local populations of Nagagaki oysters, which became extinct 30 years ago and examination of utilization of Nagagaki oysters

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07855
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Toho University
• Principal Investigator: OKOSHI Kenji 東邦大学, 理学部, 教授 (60201969)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: ナガガキ / マガキ / 絶滅 / 貝殻 / 形態 / 遺伝子 / ＣＴ

Outline of Final Research Achievements

The purpose of this study is to rediscover the Nagagaki oyster which is considered to be almost extinct in the early 1980's. The oyster, also known as the Ezogaki, is considered to be a local population of the oyster Crassostrea gigas. From 2015 to 2018, we investigated the habitats of Nagagaki type oysters from Hokkaido to Tohoku. We also fixed the samples for genetic analysis, and observed and measured specimens from museums, etc. We collected Nagagaki type individuals with a shell height of less than 30 cm from several locations in Hokkaido and Tohoku. We also confirmed the new locality. As a result of observation of shell micro structure by micro-CT, the development of shell chamber was confirmed. In the future, comprehensive analysis will be performed by the next-generation sequencer to analyze genetic characteristics of Nagagaki oyster.

Free Research Field

海洋生物学　水産増殖学　バイオミネラリゼーション

Academic Significance and Societal Importance of the Research Achievements

海洋に生息している生物の一部は人為的影響によって絶滅に瀕している。マガキの地方集団と考えられている「ナガガキ」は1980年代に「カキ島」の客土により絶滅したと考えられていたが、本研究で約30年ぶりにナガガキ型の個体を複数産地で発見した。30年前にはできなかった最新のmicro-CTや次世代シーケンサーによる解析を行い、「ナガガキとは何か？」という問いの一端を明らかにすることができた。また、本研究の成果を受けて2019年からは市役所や地元漁協等が加わって利活用の研究が開始される。本研究では資源保護の観点から調査地点及び採集地点の詳細は現時点では公表しないことを付記する。