Rotifers as live food for fish larvae: resting egg formation for various rotifer strains

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K21340
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 40:Forestry and forest products science, applied aquatic science, and related fields
• Research Institution: Nagasaki University
• Principal Investigator: Hagiwara Atsushi 長崎大学, 水産・環境科学総合研究科(水産), 特定教授 (50208419)
• Co-Investigator(Kenkyū-buntansha): 金 禧珍 長崎大学, 水産・環境科学総合研究科(水産), 准教授 (10823437)
• Project Period (FY): 2020-07-30 – 2023-03-31
• Keywords: ワムシ類 / 休眠 / 耐久卵 / カイアシ類 / 保存 / 遺伝子解析

Outline of Final Research Achievements

The rotifer used as an initial food source in aquatic seedling production forms resting eggs that stay dormant for long periods of time under dry or frozen conditions. This can be used as a simple means of preserving rotifers, but many of the rotifer strains used in aquaculture hatcheries do not produce resting eggs. In this study, we hypothesized that "any rotifer strain can form resting eggs and tested this hypothesis. As a result, it was found that it is possible to efficiently obtain resting eggs through environmental manipulation. Although some rotifer strains did not express genes related to mixis (the first stage of resting egg formation), their antioxidant stress tolerance was more than 10 times higher than that of other strains, indicating that they have strong environmental tolerance instead of forming resting eggs that avoid adverse environments.

Free Research Field

水産増殖学

Academic Significance and Societal Importance of the Research Achievements

耐久卵は、凍結や乾燥下で長期間休眠状態を維持するので、水産養殖分野では、仔魚飼育のオフシーズンにワムシの簡便な保存手段として活用できる。一方、種苗生産の現場で餌料生物として培養されている優良形質を備えたワムシの多くは耐久卵を作らないことが多く、長年の懸案となってきた。本研究を通じて、耐久卵形成能を備えたワムシ株に対し、より効率的に耐久卵を得る方法が新たに示されると共に、低温処理後の昇温で耐久卵を確保可能なワムシ株が存在することを見出した。環境操作によっても耐久卵を作らない一部の有用株は、抗酸化ストレス耐性がきわめて高いことが分かり、成体や卵の形で長期保存できる可能性が新たに示唆された。