Questions and Answers > Common Questions > General Q: Why pufferfish is poisonous? A: Pufferfish is the second most poisonous vertebrate in the world. It produces the deadly tetrodotoxin which around 1 to 2 mg for already lethal to human beings. It is estimated that a single pufferfish has enough poison to kill 30 adult humans. Although pufferfish is so toxic, it actually cannot produce toxin itself. Tetrodotoxin is produced by marine bacteria, such as Vibrio, within the pufferfish. These bacteria exist in common marine water. Some lower trophic organism, such as shellfish, sea star and angle fish also acquired these marine bacteria, but their toxin level is below the lethal amount. On the other hand, pufferfish prey commonly on these lower trophic organisms. The bacteria go up with the food chain and accumulated in the fish body. The amount of bacteria accumulated becomes hundreds times higher and toxin secreted can thus becomes lethal. This is known as the bioaccumulation and biomagnification processes. Simular processes occur in ciguatera fish poisoning in reef fish. Tetrodotoxin mainly accumulates in the liver, intestines, skin, and ovaries(eggs) of pufferfish, while their flesh are less toxic. The puffer itself has immunity to the poison due to a mutation in the protein sequence on the cell membranes. Some pufferfish can utilize their toxicity as a means of defense to predators. Since the toxin-releasing bacteria are only acquired through food, theoretically, puffers raised in captivity do not contain tetrodotoxin. Japanese are famous for eating pufferfish. Need not to mention, there are non-poisonous pufferfish maricultural researchs ongoing in Japanese. GROUPS Common Questions Misunderstandings Technical Questions CATEGORIES General Beach Fishery Red-tide Enviornmental Protection Water Treatment Scientific