Origin of tetrodotoxin and toxification mechanism in juvenile puffer fishes

河豚的河豚毒素中毒是一个重要的课题。天然河豚的毒性因地区和个体的不同而不同，养殖的河豚是无害的，这可能是食物链机制引起的中毒。在岩手县奥基莱湾，夏季和秋季都会出现剧毒的幼河豚。然后，为了对食物链机制有实际的证据，我们在Okkirai Bay进行了饲养实验。将无毒养殖的草鱼幼鱼关在浸泡在海水中的塑料鱼笼(80×56×37 cm)中，通过狭窄的缝隙摄食从外部侵入的自然生物。饲养实验在奥基拉伊湾的两个地点进行了两到四周的时间。(女泽渔港和Sodenosawa)，并在夏季和秋季重复进行三年。每次饲养实验结束后，用小鼠检测所用标本的毒性，以监测是否发生了…中毒或多或少。在Sodenosawa进行的14项实验中，没有一项显示发生了中毒。另一方面，在小泽的14个实验中，从8月到10月进行的5个实验表明发生了中毒。上述结果表明，无毒养殖的河豚幼鱼在一定时间、特定地点被海水浸泡在网箱中饲养时会中毒。在上述实验中，养殖河豚的中毒可能是通过摄取自然生物而发生的，但没有鉴定出致病微生物。然后，在下一个实验中，我们试图缩小致病微生物的范围。在大泽渔港附近设置了装有无毒养殖幼鱼的养鱼箱。分别用2 mm、0.3 mm和0.1 mm滤网依次抽吸和过滤港口海水。用0.3 mm或0.1 mm的滤网将过滤后的和浓缩的微生物提供给养殖箱，并喂给草菇。在8月至10月进行的实验中显示发生了中毒。这表明致病微生物非常小。较少

The toxification of puffer by tetrodotoxin is an important subject. The facts that the toxicity in natural puffer varied regionally and individually, and that the cultured puffer was innocuous may suggest that the toxification was caused by the food chain mechanism. In Okkirai bay, Iwate prefecture, highly toxic juvenile puffer fish appear in summer and autumn. Then, to have actual proof of the food chain mechanism we conducted rearing experiments in Okkirai Bay. Non-toxic cultured juvenile kusafugu Takifugu niphobles were confined in a plastic fish cage (80x56x37cm) submerged in seawater and fed natural living organisms intruding into the cage from outside through narrow gap. The rearing experiments were conducted for two to four weeks at two spots in Okkirai Bay. (Onisawa fishing port and Sodenosawa) and repeated during summer and autumn for three years. After each rearing experiment, the toxicity of specimens used were assayed using mouse to monitor whether toxification had occurred … More or not. At Sodenosawa among total 14 experiments conducted none showed toxification occurred. On the other hand, at Onisawa among 14 experiments 5 experiments conducted from August to October showed toxification occurred. Above result suggest that non-toxic cultured juvenile kusafugu become toxic when reared in a cage submerged in seawater in certain times at certain spots.In the experiments described above, toxification of cultured juvenile puffer was supposed to be occurred by ingesting natural living organisms, but the causative organisms were not identified. Then, in the next experiment, we tried to narrow the range of the causative organisms. Fish rearing tanks containing non-toxic cultured juvenile kusafugu were set up near Onisawa fishing port. Seawater of the port was pumped up and filtered by 2, 0.3 and 0.1 mm mesh filters respectedly and sequentially. Filtered and condensed microorganisms with 0.3 or 0.1 mm mesh filters were provided to the rearing tanks and fed to the kusafugu. In the experiment conducted from August to October showed toxication occurred. This suggests that the causative organisms are very small. Less