Ethological study about direction perception by magnetic sense of a fish

(1)在一个径向对称的实验池中，研究了日本鳗鲡在玻璃鳗阶段的方向选择性。太平洋海岸（东部人口）和东海沿岸（西种群）。他们在两个地点进行了测试。两个种群在SW-结果表明，在西海岸的地点，东方种群的方向偏好随时间和地点的不同而不同，当地磁场取消后，东方种群的方向偏好消失，这似乎是由于采集季节的不同而不同。(2)在实验室条件下，切断日本鳗鲡的嗅束，用心脏条件反射法测定其磁敏感性。对照组和假手术组对人工磁场均表现出明显的条件反射，而切断嗅束组则无条件反射。结果表明，在人工磁场作用下，日本鳗鲡嗅束的磁敏感性随磁场强度的增加而增加，但在人工磁场作用下，嗅束的磁敏感性随磁场强度的增加而增加。 关于我们 说明嗅束中含有磁敏感神经细胞，磁敏感神经细胞的鉴定有待于进一步研究。(3)对人工成熟的日本鳗鲡视网膜进行了组织学观察，并与野生黄鳗视网膜进行了比较。随着成熟，视网膜背侧区的视锥消失，视杆密度没有变化，表明成熟的日本鳗鲡视网膜具有半深海适应性。根据日本鳗鲡对低温的耐受性和黑潮水温的垂直分布，据推测，洄游的成年日本鳗鲡穿越黑潮的最大深度为600 m。(4)日本鳗鲡在没有条件反射的情况下，对地磁场的抵消产生心电反应，这一现象可用于鱼类磁敏感性的研究。(5)已被证明具有磁敏感性的弹涂鱼MUTSUGOROU在径向对称的试验箱中接受了训练，以应对特定的地磁场，但条件反射尚未完成。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