Evolution of the dinosaur respiration system revealed from the movement of the center of gravity involved with breathing

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20380
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: Tokyo University of Agriculture and Technology
• Principal Investigator: Ueda Hirochika 東京農工大学, 学内共同利用施設等, 特任助教 (20963953)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 重心移動 / 呼吸 / 鳥類 / 生物進化 / 有羊膜類 / 肋骨運動

Outline of Final Research Achievements

In tetrapods, the positions of visceral organs change with their respiration, resulting in a shift in the centroid. It has been pointed out that the position of the centroid in birds is limited to the dorso-ventral shift due to a unique joint between their rib and sternal rib, which may contribute to the bipedalism and flight ability, but this has not been verified experimentally. In this study, the centroid shifts with the respiration in birds (chickens) and squamates (Japanese geckos and leopard geckos) were measured. Furthermore, the rib movements involved with the lung exhalation and inhalation were evaluated quantitatively by CT-scanned data. The result revealed that the centroid shifts in the examined animals were small below the detection limit. In light of the quantitative analysis of CT data, this may be because only first to third ribs contribute to respiration in geckos, resulting in small centroid shifts.

Free Research Field

進化古生物学

Academic Significance and Societal Importance of the Research Achievements

本研究はDuncker (1979)が予想した有羊膜類の重心移動の仮説をもとに、呼吸運動と重心位置の関係性の進化史の解明を目指したものである。
本研究の結果はDuncker(1979)の仮設の前提条件、すなわち四足性動物の重心が呼吸運動に伴って前後に移動するという推定がそもそも誤りである可能性を示唆するものであった。一方で重心の移動を制限していると推定されるメカニズムはそれぞれおことなっており、呼吸を駆動する肋骨運動は複雑な進化を経ている可能性が明らかになった。これらの結果は生物進化における物理学的な制約という側面を明らかにするうえで、重要な手掛かりとなると期待さ入れる。