Ethological study about direction perception by magnetic sense of a fish

(1)在径向对称试验池中研究了日本鳗鲡在玻璃鳗期的方向偏好。我们使用了来自两个地方的两个玻璃鳗种群；太平洋沿岸（东部人口）和东海沿岸（西部人口）的九州。他们在这两个地点进行了测试。西海岸种群对SW-S均有方向性参考，而东部种群对SW-S的方向性偏好在不同年份和试验点表现出不一致。当地磁场取消后，方向性偏好消失。根据玻璃鳗采集季节的不同，其方向偏好似乎有所不同。(2)切开日本鳗鲡的嗅束，在实验室用心脏调节法测定其磁敏感性。而对照组和假手术标本对人工磁场均表现出明显的条件反应，而嗅觉束切断标本则没有条件反应，进一步说明嗅觉束中含有磁敏感神经细胞。磁敏神经细胞的鉴定将在未来的研究中进行。(3)对人工成熟日本鳗鲡的视网膜进行了组织学检查，并与野生黄鳝视网膜进行了比较。视锥细胞在视网膜背侧消失，而视杆细胞密度不随成熟而变化，表明成熟鳗鱼视网膜已适应半深海环境。根据鳗鲡的低温耐受性和黑潮水温的垂直剖面，假设成年鳗鲡洄游的最大深度为600 m。(4)日本鳗鲡在不加任何条件的情况下，对地磁场的消除表现出相应的心电图反应。这一现象可应用于鱼类的磁敏性检测。(5)跳泥鱼MUTSUGOROU已被证明是磁敏感的，在径向对称的试验槽中，训练它在特定的地磁场下进入避难所，但条件调节尚未完成。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