Investigating the mechanism of yellow coloration in the koi carp

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K19217
• 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: Kitasato University
• Principal Investigator: Mizusawa Kanta 北里大学, 海洋生命科学部, 教授 (70458743)
• Co-Investigator(Kenkyū-buntansha): 天野 春菜 北里大学, 海洋生命科学部, 講師 (50431341)
• Project Period (FY): 2022-06-30 – 2024-03-31
• Keywords: ニシキゴイ / 体色 / 皮膚 / 色素 / カロテノイド / プテリジン / 液体クロマトグラフィー質量分析法 / 酵素

Outline of Final Research Achievements

This study focused on two varieties of koi carp: the red-patterned Kohaku and the yellow-patterned Kijiro. It investigated the red and yellow pigment components in these varieties and the genes involved in the metabolism and biosynthesis of the pigments. As a result, it was found that Kijiro accumulates zeaxanthin, a yellow-colored carotenoid abundant in their diet, directly in their skin. In contrast, Kohaku converts zeaxanthin to astaxanthin, a red-type carotenoid that accumulates the ester forms of astaxanthin in their skin. A method was also determined for extracting and analyzing pteridine, a red/yellow pigment different from carotenoids, from fish skin. Furthermore, by comparing genes expressed in the skin of koi carp varieties, we found several candidate genes involved in carotenoid metabolism and pteridine biosynthesis.

Free Research Field

魚類生理学

Academic Significance and Societal Importance of the Research Achievements

本研究により、ニシキゴイの体内におけるカロテノイドの代謝・蓄積メカニズムに基づいた、新たな色揚げ飼料の開発の基盤となる知見が得られた。また、ニシキゴイの皮膚に含まれるプテリジンを分析することにより、今後、色揚げ餌によらない赤・黄色系の色揚げ技術が生まれることが期待される。また、カロテノイド代謝とプテリジン生合成に関わる遺伝子の発現に関わる環境要因や品種間の遺伝子の違いを解明することによって、体色への影響を考慮した飼育環境の改善や、遺伝子判別に基づいた新たな選抜育種法の開発が進むことが期待される。