What is Venerupin?

a photo of oyster As this is an extremely lethal toxin, there are reports of cases of poisoning in some types of oysters and Asari (short-necked clams). The source of the Venerupin is said to be the intake of toxic dinoflagellate. This only occurs in early Spring in Nagai, Kanagawa prefecture and Lake Hamana in Shizuoka prefecture and in one instance over 100 people died. However, as there have been no incidents of poisoning since 1950, it’s still not clear if the shellfish actually become toxic or not.

In most cases, the toxic symptoms appear within one to two days and start with abdominal pain, vomiting, constipation, etc., followed by blood spots on the skin and bleeding from the mouth and nose. Liver function also significantly decreases and the patient suffers from mental derangement. They then fall into a coma and die within a few days.


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Revision date: January 5, 2023

What is Palytoxin?

a photo of Figured leather jacket
Colorful-looking fish are often poisonous.

Figured leather jacket (luterus scriptus) is a type of large filefish that lives in the warm seas of the world. The meat is used to make kamaboko (boiled fish paste), but there have been cases of poisoning from this fish in various places including Okinawa, Saipan and Tahiti. The toxin found through research was given the name Palytoxin.

With Palytoxin, Palythoa tuberculosa is generated and it is a highly toxic substance that accumulates in various sea creatures through the food chain. It is considered to be even more toxic than that of blowfish. Even heat does not break down this toxin

The toxicity symptoms suddenly appear between 3 to 36 hours after consumption. However, vomiting and diarrhea are not normally occurring symptoms. The main symptoms of this poisoning include intense muscle soreness starting in the trunk near the limbs, followed by muscle weakness. Finally, coronary artery spasms occur, causing death. Cases of poisoning in Japan are well-known to be caused by the intake of Scarus ovifrons, and there are also reports of Epinephelus bruneu, Ostracion immaculatus, Lactoria diaphana, Aluterus scriptus, etc. Cases have occurred in Kyushu and Shikoku, such as Kagoshima, Miyazaki and Kochi prefectures.


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Revision date: December 1, 2022

What is Saxitoxin?

a photo of Midgut gland hotategai
The black area of the Scallop is the midgut gland.

Scallops sometimes eat a type of toxic dinoflagellate (known as the cause of the red tide), accumulate this toxin in their bodies and become poisonous. This toxin is called Saxitoxin and it has a high fatality rate.

Symptoms of poisoning start with numbness in the lips, tongue and side of the face as well as a burning sensation that eventually spreads to the ends of the limbs and causes loss of sensation. When it gets even worse, the victim loses the ability to move their body. Even in end stage, the victim maintains consciousness until breathing ceases and then finally dying from suffocation. There have been a number of cases of death from Saxitoxin on either coast of the North American continent, but there are very few cases of poisoning in Japan.


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Revision date: November 25, 2022

What is Ichthyohemotoxin?

a photo of anago blood
Fillet Anago and then make nigiri sushi.

Among the fish that belong to the Anguilliformes order such as Eel, Conger eel, and Moray eel, some contain toxic components in their blood serum. This type of serotoxin is called Ichthyohemotoxin and indicates lethal and hemolytic actions. However, this is not the official name of the toxin, and the chemical structure is also not clear.

If a human were to drink a large amount of fresh blood from these fish, they would suffer from symptoms such as diarrhea, constipation, vomiting, cyanosis, arrhythmia, paresthesia, paralysis and respiratory distress, and it would then sometimes result in death. If the blood gets in your eyes, it causes an intense burning sensation, swollen eyelids, and a foreign body sensation that last for days. Sufficient caution must be practiced when preparing these fish, but there is no concern for toxicity if it is cooked. Incidentally, in case of Ichthyohemotoxin, found in eel’s blood, the toxicity completely disappears when cooked for 5 minutes at 60℃, so there are no issues with eating eel Kabayakai.


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Revision date: November 15, 2022

What is Ciguatera fish poisoning?

a photo of Star snapper

Ciguatera fish poisoning is a type of food poisoning caused by consuming certain fish that live in tropical and subtropical coral reef areas such as Moray eel, Grouper, Star snapper, Japanese scavenger and Parrot fish.

It is caused by toxins such as ciguatoxin, but it mainly generates from dinophyceae that are stuck to algae. The process of ciguatera occurring involves the food chain. Even if a fish itself doesn’t originally contain toxins, an herbivorous fish may eat algae that turns it toxic. That fish may be eaten by a carnivorous fish, which then accumulates high concentrations of ciguatera in its body. When a human consumes the carnivorous fish it can cause food poisoning in the human. There are as many as 300 species of fish that contain ciguatoxin. The ciguatoxin, which causes the food poisoning, cannot be killed by boiling or grilling, so it can’t be prevented through food preparation.

Symptoms of this food poisoning mainly consist of sensory nerve abnormalities, muscle soreness, itchiness and abdominal pain, but it is rarely fatal. However, it takes quite a long time to recover from compared to other toxins and the average recovery time is said to be two to three weeks. It is vital to diagnose ciguatera fish poisoning as soon as possible. Most symptoms develop within one or two hours and up to to 24 hours after consumption and one unique symptom is dysthermesthesia. This is a form of dysesthesia in which touching cold things feels like its burning. It occurs one to two days after the poisoning and is a known characteristic of ciguatera fish poisoning. Another characteristic symptom of ciguaterafish fish poisoning is joint pain within 24 hours after consuming the fish. In any case, it is important to be seen by a specialist as soon as possible.

Incidentally, the name ciguatera came from Spanish immigrants to Cuba as a name for food poisoning caused by the cigua shellfish in that region. Later it was also used to describe fish poisoning, which causes similar symptoms.


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Revision date: May 9, 2022

What is Fugu poison?

In most cases, Fugu (blowfish) poison is found in non-meat parts of the fish such as the liver, ovaries, stomach, intestine, skin and eyes. There are Fugu that do not contain poison in these parts, but most of the Fugu in the waters near Japan are poisonous. A mistake in preparations that allows the meat to touch the poison of the liver or ovaries results in immediate death. Therefore, the general rule is to only eat Fugu at restaurants with an expert licensed in Fugu preparation. Cases of poisoning by Fugu are nearly always a result of an amateur trying to prepare the fish.

The toxin in Fugu is a chemical substance called tetrodotoxin and even heat from boiling or frying can’t detoxicate it. Even Torafugu (Japanese pufferfish) that we find so delicious (we eat the meat, skin and testes) has poison in the liver, ovaries and intestines. The toxicity is said to be at least 1,000 times that of potassium cyanide. They say 10 people would die from the organs of a single Torafugu. In the case of Fugu poisoning, the first poisoning symptoms occur between 20 minutes and three hours after eating the Fugu. It starts with numbness in the lips, the tip of the tongue and fingertips. This is followed by headache, stomachache and severe vomiting. The victim will stagger when trying to walk. Soon they will experience sensory paralysis, speech disturbance and difficulty breathing, accompanied by a decrease in blood pressure. After that, the entire body becomes paralyzed and the victim can no longer move even a finger. Finally, they will fade out of consciousness and eventually both breathing and heartbeat cease, resulting in death. If the consumer doesn’t notice they are experiencing poisoning symptoms, they will surely die.

The strength of the toxin of the fugu also varies depending on the season. Even on an individual basis, some fish have toxins while others don’t. It’s not possible to determine this based on appearance, so it’s better to never eat the organs and eyes, which have a high probability of containing poison.

Fugu has already been successfully farmed and is on the market. No toxins have been found in this farmed Fugu. If farmed Fugu has no toxins, it’s only natural to question what factors generate toxins in wild Fugu and apparently it‘s a cumulative effect of toxins from the food chain. Fugu’s main sources of nutrition are starfish and shellfish. Starfish and shellfish accumulate poison in the body by eating zooplankton with vibrio attached to them. This vibrio creates poisons. Then, Fugu accumulates toxins in the body by eating starfish and shellfish that have toxins accumulated in their bodies. Therefore, farmed Fugu are raised on man-made feed that doesn’t contain Fugu toxins, and since they don’t ingest Fugu toxins and there is no bioconcentration, so the Fugu does not contain poison.


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Revision date: February 1, 2021