Sperm competition occurred in spawning of masu salmon

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K07229
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Ecology/Environment
• Research Institution: Nihon University
• Principal Investigator: MAKIGUCHI Yuya 日本大学, 生物資源科学部, 講師 (00584153)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 代替繁殖戦略 / サクラマス / 精子運動

Outline of Final Research Achievements

Masu salmon exhibits typical fixed male alternative reproductive tactics. The large anadromous males fight before spawning to achieve dominant access to the females, whereas the small parr males adopt a sneaker tactic to dart into spawning events and furtively position themselves under ovipositing females to release milt near the female as she releases her eggs and ovarian fluid. Sperm competition theory predicts that milt from multiple males enhance the fertilization competition because serum included in milt affect the sperm velocity, which is one of the important factor to determine the success of fertilization. The objective of this study is to investigate effect mixture of milt from parr males and anadromous males on hatching rate of eggs. Hatching rate was higher in mixture of parr and anadromous males than in same tactics group. Our results indicated that mixture of milt from parr and anadromous males improve the quality of hatching eggs.

Free Research Field

行動生態学、水産学

Academic Significance and Societal Importance of the Research Achievements

本研究では精子速度が精漿や体腔液などの生体由来の成分に影響を受けることを明らかにした。精子運動性能、特に精子遊泳速度が雄の繁殖成功に大きな影響を与える要因として考えられて来た(Gage et al., 2004)。しかし、過去に測定された魚類の精子遊泳速度は河川水または海水などの無機的な溶媒を用いたものが大半であった。体外受精を行う魚類の受精環境では競争雄の精漿や雌の体腔液が多くの場合存在しており、これまで測定されてきた精子速度とは異なる可能性がある。本研究課題は、精漿が雄の繁殖成功に寄与する可能性に着眼している点が独創的であり行動生態学研究に新しい知見をもたらすことが期待される。