2021 Fiscal Year Final Research Report
Structural evolution of the mandibular feeding system in Ostracoda –Overcome of the bauplan dilemma in bivalved arthropods-
| Project/Area Number |
18K06388
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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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| Review Section |
Basic Section 45030:Biodiversity and systematics-related
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| Research Institution | International University of Health and Welfare |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Keywords | 節足動物 / 貝形虫類 / 大顎類 / カンブリア紀 |
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| Outline of Final Research Achievements |
I have carried out SEM observations of the mandibular gnathal edges in the 6 superfamilies of living Ostracoda and completely established the methods of TEM observations. Then, TEM observations of the mandibular gnathal edges also have done in these taxa to understand the ultrastructures of the sensory nervous system inside there. Further, I have succeeded in reconstruction of the mandibular skeleto-musculature system in some podocopids with the serial light-microscopic sections. Based on these results, it is concluded that some ostracods accomplish “mandible for biting”, which is an exceptional among the bivalved arthropods, due to “optimized incisors”, “numerous sensilla”, “powerful adductor and abductor muscles” and “stable fulcrum”. This mandible allows the ostracods to have a broader range of food choice then other bivalved arthropods and is also used in their valve opening system.
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| Free Research Field |
形態学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究成果は，貝形虫類という微小甲殻類をモデルとして，二枚殻節足動物が如何にして“物を噛む”という基本的動作を達成しているかを明らかにした．本分類群の大顎と形態的に酷似した化石が，後期カンブリア紀の地層から産出している事実は，初期カンブリア紀に出現したとされる節足動物の大顎類は，後期カンブリア紀までに現生種と比肩するレベルの大顎咀嚼系を構築していたことを示す．我々脊椎動物の祖先がカンブリア紀に出現し，デボン紀に顎を獲得するまで３億年近い年月を要した事実と対比すると，節足動物に生じた「大顎革命」は，まさに異例と言える進化的イベントであることが，本研究成果によって明確に浮き彫りとなった．
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