Ethological study about direction perception by magnetic sense of a fish

(1)在径向对称的水槽中考察了日本鳗在玻璃鳗阶段的定向偏好性。九州太平洋沿岸(东部种群)和东中国海岸(西部种群)在两个地点进行了测试。这两个种群在西海岸地点的西南S都表现出方向偏好，而东部种群在不同年份和测试地点表现出不一致的方向偏好。当地磁场被取消时，方向偏好消失了。似乎方向偏好随着玻璃鳗采集季节的不同而不同。(2)切断日本鳗的嗅束，然后在实验室用心脏条件反射方法测试它们的磁敏性。而对照和假手术标本都显示出明显的条件性对人工磁场的反应和嗅束切断的标本没有出现条件性反应，INDIC…对人工成熟的日本鳗的视网膜进行了组织学检查，并与野生黄鳗的视网膜进行了比较。视锥细胞消失在视网膜背侧，视杆密度没有随着成熟而改变，表明成熟鳗鱼的视网膜是半深海适应性的。根据鳗鱼的低温耐受性和黑潮洋流中水温的垂直分布，据推测，迁徙的成年日本鳗鱼在最大深度600m处穿过黑潮。(4)日本鳗鱼在没有条件的情况下，对地磁场的抵消表现出心电图反应。这一现象可用于鱼的磁敏试验。(5)在径向对称的测试水箱中，对特定的地磁场进行了训练，使日本鳗MUTSUGOROU对特定的地磁场做出反应，但条件反应并未完成。较少

(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 … More 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