Elucidation of the role of adipose tissue in cetacean reproduction

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K20373
• Project/Area Number (Other): 18H05362 (2018-2019)
• Research Category: Grant-in-Aid for Challenging Research (Pioneering)
• Allocation Type: Multi-year Fund (2020); Single-year Grants (2018-2019)
• Review Section: Medium-sized Section 40:Forestry and forest products science, applied aquatic science, and related fields
• Research Institution: Mie University
• Principal Investigator: Yoshioka Motoi 三重大学, 生物資源学研究科, 教授 (30262992)
• Co-Investigator(Kenkyū-buntansha): 鈴木 美和 日本大学, 生物資源科学部, 教授 (70409069) ; 船坂 徳子 三重大学, 生物資源学研究科, 准教授 (50616175)
• Project Period (FY): 2018-06-29 – 2023-03-31
• Keywords: イルカ / 脂皮 / 脂肪 / ホルモン / 繁殖 / 水温 / 性ステロイド / 生検

Outline of Final Research Achievements

Regarding the physiological involvement of the thick subcutaneous adipose tissue called blubber, which is a characteristic tissue of cetaceans, in the reproductive function, we conducted biweekly blood sampling and seasonal collection of blubber tissue using a newly developed biopsy device from captive sexually mature and immature common bottlenose dolphins. Using these samples, we performed hormone concentration measurement, genetic analysis, and fat analysis. As a result, the following points were clarified; 1) Fat composition differed greatly between epidermis and subcutaneous fat (three layers); 2) Approximately 40 physiologically active substances were expressed in subcutaneous fat at levels equal to or higher than those of leptin; 3) Composition of fatty acids bound to neutral lipids showed characteristics suggestive of cold adaptation; and 4) Circulating cortisol levels increased during the cold season.

Free Research Field

鯨類の繁殖生理学

Academic Significance and Societal Importance of the Research Achievements

ある水族館で繁殖しないイルカを，温度帯が異なる別の水族館に移動させた途端に繁殖に成功した例が複数ある．これはその繁殖に水温が深く影響していることを示唆している．そこで，鯨類には哺乳類には例をみない，脂皮と呼ばれる厚い脂肪組織が全身を覆うことに着目し，脂皮中の脂肪組織と繁殖との関わりをホルモン・遺伝子・脂肪の3つの異なる視点での分析により調べた．その結果，これまでまったく知見のなかった脂肪組織から産生される約40を超える生理活性物質やホルモン，水温変化と繁殖との生理学的関係が明らかになるとともに，鯨類における脂皮が果たす新たな生理学的機能と飼育環境における水温管理の重要性を指摘することができた．