The pufferfish is a type of marine fish, with over a hundred species found worldwide, and about 40 of which are found in China. The main species that often cause human poisoning include the starry puffer and the leopard puffer.
The toxicity of the pufferfish is caused by tetrodotoxin present in its body. The chemical name of tetrodotoxin is 6-hydroxy-8-(hydroxymethyl)-4-methoxyazepane-2-carboxylic acid, and it is a highly toxic substance. The amount of toxin contained in pufferfish varies by gender, part of the fish, and season. Generally, the ovaries and liver contain the highest amount of toxin, making them the most poisonous, followed by the kidneys, blood, eyes, gills, and skin. The fresh, cleaned flesh of most species can be considered non-toxic. However, after the fish dies and is stored for a period, the flesh can become contaminated with the toxin. Spring is the ovarian development period for female pufferfish, when the ovarian toxicity is at its peak. Combined with the highest liver toxicity in spring, this is the season when pufferfish poisoning is most likely to occur. In summer and autumn, after the female fish have spawned, the ovaries degenerate and their toxicity decreases.
Tetrodotoxin is a non-protein, highly active neurotoxin that is slightly soluble in water and easily soluble in vinegar. It is stable at a pH of 3-6, but is easily destroyed when the pH is greater than 7. It is extremely stable to light and heat; it cannot be completely destroyed after 6 hours at 100°C. Pufferfish flesh soaked in a 2% sodium carbonate solution for 24 hours and then washed can be considered non-toxic.
After entering the human body, tetrodotoxin inhibits the permeability of nerve cell membranes to sodium ions, thereby blocking the conduction of nerve impulses and causing nerve paralysis. The incubation period is generally 0.5-3 hours. The main symptoms of poisoning include: initial facial flushing, headache, severe nausea and vomiting, abdominal pain, and diarrhea. This is followed by sensory nerve paralysis, such as numbness and tingling in the lips, tongue, and fingers. Then, motor nerve symptoms appear, such as muscle weakness and difficulty moving in the hands, arms, and legs, causing the body to sway, a numb tongue, unclear speech, and even paralysis due to numbness of the whole body. In severe cases, blood pressure may drop, bradycardia (slow heart rate), and difficulty in breathing may occur, leading to death from respiratory failure. Due to the extreme toxicity of pufferfish, national regulations prohibit the sale or consumption of pufferfish.