2006 Fiscal Year Final Research Report Summary
Ethological study about direction perception by magnetic sense of a fish
| Project/Area Number |
17560045
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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 |
Applied physics, general
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| Research Institution | Kagoshima University |
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Principal Investigator |
NISHI Takaaki Kagoshima University, Faculty of Fisheries, Assistant professor, 水産学部, 講師 (30237656)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAMURA Gunzo Kagoshima University, Faculty of Fisheries, professor, 水産学部, 教授 (30041718)
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| Project Period (FY) |
2005 – 2006
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| Keywords | glass eel / orientation behavior / magnetic sense / unconditioned response / directional preference / retina |
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| Research Abstract |
(1) The directional preference of the Japanese eel at the glass eel phase was examined in a radially symmetric test tank.We use d two glass eel populations from two localities; Pacific Ocean coast (east population) and East China Sea coast (west population) of Kyushu.They were tested at the two locations.Both populations showed directional p reference in SW-S on the west coast site while the east population showed inconsistent direction preferences by year and test site.The directional preference disappeared when the geomagnetic field was cancelled.Itseemed that the direction preference differed depending on the glass eel collection season.
(2) The olfactory tracts of the Japanese eels were cut and then their magnetosensitivity was tested by the cardiac-conditioning method in a laboratory.While both the control and sham operated specimens showed clear conditioned responses to an artificial magnetic field and the specimens with olfactory tract cut presented no conditioned response, indic
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ating that the olfactory tract contains magnetosensitive nerve cells.Identification of the magneto sensitive nerve cells will be addressed in a future study.
(3) The retina of the artificially matured Japanese eels were histologically examined and compared with the retina of wild yellow eels.The cones disappeared in the dorsal retinal region while the rod density did not change with maturation, indicating a semi-deepsea adapted retina in the mature eels.Based on the low temperature tolerance of the eel and the vertical profile of water temperature in the Kuroshio Current, it is postulated that the migrating adult Japanese eel cross the Kuroshio Current at a maximum depth of 600 m.
(4) Japanese eel showed electrocardiogram responses in response to the cancellation of the geomagnetic field without a conditioning.This phenomenon could be applied to the examination of the magnetosensitivity in fishes.
(5) The mud-skipper, MUTSUGOROU which had been shown to be magnetosensitive, was trained to come a shelter in response to a specific geomagnetic field in a radially symmetric test tank, but the conditioning was not completed. Less
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