Why Ziphiid stomachs are so peculiar?

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06791
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45030:Biodiversity and systematics-related
• Research Institution: National Museum of Nature and Science, Tokyo
• Principal Investigator: YAMADA Tadasu 独立行政法人国立科学博物館, その他部局等, 名誉研究員 (70125681)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: アカボウクジラ科鯨類の複胃 / 複胃の部位ごとの機能 / 腹腔内の胃のあり方 / 展示標本作成 / 胃内微生物叢

Outline of Final Research Achievements

(1) Detailed morphological investigation was carried out on neonate ziphiid whales (a whole body and 1cm thickness sliced sections), referencing CT data, and clarified the topographical anatomical relationship with the mesogastric ligament and omentum, etc. (2) Contents of the separated chambers were collected from four ziphiid whale species and eDNA analyses were made. eDNA data from each small chambers of the stomach were collected and comparative analyses were made to explain the necessity of these small chambers. in order to prove the digestive specificity of these small chambers of ziphiid cetacean stomachs with the gastric microbiota. However, dominant microorganism flora was not specified, and individual differences were large. We need to continue further analyses. (3) We prepared gastric plastination specimens of four beaked whale species to clearly show the specific multi\chambered stomoach of the ziphiid whales.

Free Research Field

海棲哺乳類学

Academic Significance and Societal Importance of the Research Achievements

鯨類は動物食であるにも拘わらず，複胃（複数の部屋に分かれた胃）や，長い腸管をもつ．なかでもアカボウクジラ科鯨類は種によっては10をこえる多数の小部屋に分かれているが，これは「謎」とされている．本研究では，CT画像を参照しながら，アカボウクジラ科鯨類新生児の解剖学に精査し，小部屋に分かれた複胃の発生学的な経過を解明した．これらの小部屋は胃の内部環境を区画しているので，小部屋ごとの内容物の遺伝子解析により，隔離された環境に特異的な微生物が存在して消化機能を維持している可能性を検証しようとしたが今回は果たせなかったが，胃内微生物叢の解析をさらに進めてかれらの消化機能を検証する初の試みだった．