| Project/Area Number |
06640601
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | University of the Ryukyus |
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Principal Investigator |
TABUKI Ryoichi University of the Ryukyus, College of Education, Associate Professor, 教育学部, 助教授 (60155231)
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| Co-Investigator(Kenkyū-buntansha) |
HANAI Tetsuro Osaka Gakuin University, Law Department, Professor, 法学部, 教授 (70011442)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1995: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1994: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | ostradodes / saipanettid genus / submarine cave / coral reef / troglobitic / microhabitat / predator / competetor / 生きている化石 / サンゴ礁 / 付属肢 / 生態 / 洞窟環境 / 分類学 / ジュラ紀 / 生き残り戦略 |
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| Research Abstract |
The puropose of this study is to reveal the faunal characteristics of the submarine cave ostracodes from the Ryukyu Islands, and the evolutionary process of the new troglobitic saipanettid genus.
The characteristics of the cave assemblages from "Daidokutsu" of Ie Island are enumerated as follows. (1) Living individuals are very rare. The rare occurrence of living ostracodes probably reflects the oligotrophic conditions of submarine caves. (2) The ostracode assemblages from "Daidokutsu" consist mostly of shallow water elements from outside the cave. Exceptionally, three saipanettid species, including 'new genus' (1sp.), are all thought to have derived from deep-sea ancestors. (3) Cytheraceans from the "Daidokutsu" samples are relatively low in species diversity and individual abundance compared to other ostracode taxa. The ostracode assemblages from various habitats of open sea floor environments have been dominated by cytheraceans since the middle Jurassic.
A new troglobitic saipanettid genus, only found from submarine caves of the Ryukyu Islands, possibly derived from the saipanettid Cardobairdia, a deep-sea muddy bottom inhabitant, or its relatives. It is likely that the new genus has successfully colonized hard substrata in caves, particularly exploiting the crevices on cave walls and ceilings as its microhabitat. The new genus may have adapted to this cryptic habitat in response to strong cytheracean competetors, and to predators such as gastropods that do not survice well in dark and oligotrophic submarine caves. Insofar as well preserved appendages have been investigated, the new genus differs from the closely related genera Saipanetta and Cardobairdia in having fewer setae without any fine structure. While crawling, the new genus keeps its carapace widely gaped. The ability to open the carapace widely is one of the primitive behavioral features of podocopids.
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