| Project/Area Number |
17K05693
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Kyoto University |
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Principal Investigator |
Ubukata Takao 京都大学, 理学研究科, 教授 (00293598)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2019: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2018: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2017: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
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| Keywords | アンモナイト / 外殻性頭足類 / 機能形態 / 静水力学 / 流体力学 / 殻強度 / トレードオフ / 形態空間 / アンモノイド / 姿勢の安定性 / 搖動 / オウムガイ / パレート最適 / 比表面積 |
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| Outline of Final Research Achievements |
Ammonoids have a chambered conch that serves as a buoyancy apparatus, and hydrostatic and hydrodynamic properties that depend on conch geometry may be critical for their locomotion. Meanwhile, the shell wall should be mechanically strong enough to support the conch against hydrostatic pressure. The present analyses using a theoretical morphologic model revealed a functional trade-off between hydrostatic and hydrodynamic efficiencies. A positive correlation between relative shell thickness and hydrostatic efficiency found in this study suggests that density control was critical for ammonoids and a hydrodynamically efficient shell shape is hardly realized without sacrificing shell strength. The morphometric result shows the followings: 1) prolecanitids tend to be optimized for hydrodynamic efficiency, but some goniatitids seem to be inefficient for nektonic mode of life; 2) nautilids are optimized for hydrostatic efficiency, while tarphycerids tend to be optimized for postural stability.
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| Academic Significance and Societal Importance of the Research Achievements |
アンモナイトの流体力学特性に関する研究は半世紀にわたる歴史を有するが，なぜアンモナイトの殻形態が遊泳に適した究極の流線形に収斂せず，多様な殻形態が見られるのかが議論されてきた．一方，静水力学特性や殻の強度，殻形成効率など幾つかの観点から機能形態学的研究が進められてきたが，アンモナイトの形態的多様性はそれら異なる機能への適応の結果として理解されてきた．本研究は，そうした従来の定性的な解釈を踏まえて，アンモナイトあるいは外殻性頭足類の形態的多様性が，想定される機能的要請の折衷戦略としてある程度説明できることを，機能-形態空間解析の方法によって分析的に示した．
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