2009 Fiscal Year Final Research Report
Effect of heavy metal accumulation in sandy tidal flats of Ariake Bay on the shell forming and survival of juvenile short-neck clam.
| Project/Area Number |
19580223
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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 |
General fisheries
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| Research Institution | Kumamoto Health Science University |
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Principal Investigator |
TAKAHASHI Tohru Kumamoto Health Science University, 保健科学部, 教授 (70369122)
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| Co-Investigator(Kenkyū-buntansha) |
HIROAKI Tsutsumi 熊本県立大学, 環境共生学部, 教授 (50197737)
NOMURA Yuji 広島大学, 大学院・医歯薬総合研究科, 助手 (80218370)
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| Project Period (FY) |
2007 – 2010
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| Keywords | アサリ / 有明海 / マンガン / 干潟 / 稚貝 |
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| Research Abstract |
It has been known that shells of juvenile short-neck clam, Ruditapes philippinarum, become weak in some of the sandy tidal flat of Ariake Bay where the concentration of Mn in the pore water was higher than other tidal flat. In the present study, we confirmed that concentration of Mn in the pore water ofeach tidal flat reflects the original concentration of Mn in the river that flows in. Then, exposure experiment of Mn to the juvenile clams was carried out based on the assumption that juvenile clams had physiological impact by exposure of Mn resulting weakness of the shell. Several enzyme activities, acetylcholinestrase, metallothionein, etc. were measured, or comprehensive research of peptides in the mantle cells by Direct TOF-MS method. As a result, activities of acetylcholinestrase and carboxylesterase decreased significantly when exposed to high concentration of Mn(20ppm)with sand. It was suggested that the high concentration manganese exposure give the stress to the juvenile clam's shell formation. On the other hand, reproduction of human osteoblastic MC3T3-E1 cells was suppressed when exposed to Mn, while the activity of osteopontin and osteocalcin. We also examined direct effect of Mn to the shell, and Mn concentration in the shell of adult clams were higher in Arao tidal flat where mass mortality of juvenile clams had been recorded. Therefore, we should examine the second hypothesis that direct effect of Mn to the juvenile shell is concerned the weakness of shells and mass mortality just after the settlement. We are observing the microstructure of the shell and present state of Mn in the shell by using SEM/EDX. Consequently, high concentration Mn obstructed the shell formation while giving a physiological stress to the juvenile clam, was taken directly into the shell, and thought that the vulnerability of the shell was increased.
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