Clarification of shell color of Corbicula clam: Why do Bekko Shijimis occur.

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05789
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40040:Aquatic life science-related
• Research Institution: Kansai Medical University
• Principal Investigator: Kusumoto (Takemoto) Kuniko (竹本邦子) 関西医科大学, 医学部, 准教授 (80281509)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: Corbicula / 殻皮 / Fe-DOPA錯体 / 黒色化 / ラマン分光法 / X線微細構造 / 配位子交換

Outline of Final Research Achievements

The shell color of Corbicula clams is roughly divided into yellowish and blackish. To elucidate the origin of the blackening substance of the shell, analysis of the shells of three native Japanese Corbicula species were conducted using X-ray absorption fine structure spectroscopy, Raman spectroscopy, and attenuated total reflection infrared spectroscopy. We found that the formation of an iron (Fe)-L-3,4-dihydroxyphenylalanine (DOPA) complex in a thin organic layer, called the periostracum, on a calcareous layer causes the blackening of the shell. The results indicate that dissolved Fe-organic complexes diffuse from the aqueous environment to the periostracum, forming Fe-DOPA complex through ligand exchange. Our findings show that the water environment in which Corbicula clams live may be a significant factor in determining shell color.

Free Research Field

Ｘ線分析

Academic Significance and Societal Importance of the Research Achievements

本研究は，黄色を帯びた貝殻のシジミは砂地で，黒色を帯びた貝殻のシジミは泥地で育つ傾向にあるという，これまで経験的に知られていた知見に対し，初めて科学的な分析と検討を行ったものである。黒色化の原因物質の同定と形成化メカニズムを解明したことで，貝殻の色から，生育環境履歴を読み出すことができるようになる。これにより，シジミの成長に最適な底質環境を明らかにすることが可能となり，資源復活への貢献が期待される。