| Project/Area Number |
15540450
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Joetsu University of Education |
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Principal Investigator |
AMANO Kazutaka Joetsu University of Education, Faculty of School Education, Associate Professor, 学校教育学部, 助教授 (50159456)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Drilling predation / Cenozoic / bivalves / temporal pattern / Escalation |
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| Research Abstract |
This study examines the temporal variation of drilling predation by gastropods as naticids which is adequate for verifying "Esclation" during the Cenozic in the northern Pacific region. Consequently, the following six conclusions have been obtained. (1)The early Pleistocene Honshu populations of Glycymeris yessoensis, G.nipponica and Tridonta borealis show higher drilling intensities than those in Hokkaido. This result is concordant with the equator-ward increase of drilling intensity claimed by Dudley and Vermeij (1978), Allmon et al. (1990) and Alexander and Dietl (2001). (2)No temporal trend in the intensity of drilling on G.yessoensis by naticids during the late Cenozoic is recognized while the Pliocene population of T.borealis show lower intensities than the Pleistocene populations. (3)Drilling-site shifts are depend on the species of predator and prey (G.yessoensis, T.borealis and Calyptogena pacifica). (4)Edge drilling of G.yessoensis and T.borealis first appeared in the early Pleistocene populations, consistent with Vermeij and Roopnarines (2001). (5)Correlation coefficients of predator-prey size in G.yessoensis and T.borealis are highest in the Pliocene and lowest in the middle Pleistocene. This seems to be contradictory to "Escalation". However, such change possibly reflects he local environmental differences. (6)Drilling predation on the deep-water chemosynthetic bivalves as vesicomyids and thyasirids has been observed from the Eocene to the Miocene. In the case of the Miocene Morai Formation in Hokkaido, high intensity like as shallow-water species was recognized in C.pacifica.
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