The habitat of the venomous blue-ringed octopus (Hapalochlaena fasciata), which has a toxicity level ten times higher than that of cyanide, is expanding along the east coast of South Korea. In particular, May is the month during which blue-ringed octopuses have been found most frequently in South Korea in the last 11 years, so people living near the coast should be cautious.
The blue-ringed octopus is a species that is widely distributed in tropical and subtropical rocky reef habitats in Southeast Asia, Australia, and elsewhere, and is about 10cm in size with blue rings on its back and arms. It contains tetrodotoxin (TTX), a neurotoxin known as pufferfish poison, which is ten times stronger than cyanide. The toxin can kill 26 adults in just a few minutes and can cause symptoms such as respiratory arrest, heart failure, paralysis, blindness, and suffocation. The blue-ringed octopus stores the toxin in its salivary glands and uses it to paralyze its prey.
The distribution range of the blue-ringed octopus is spreading from the tropical regions to Japan, the Korean coast, and elsewhere. A spokesperson for the National Fisheries Research and Development Institute said, “It is believed that the blue-ringed octopus is moving northward as ocean temperatures rise due to global warming.”
In fact, a paper compiled by a research team from the National Fisheries Research and Development Institute, which summarizes the cases of blue-ringed octopuses found in Jeju, South Korea, from 2012 to 2021, shows that they were confirmed about 26 times in 11 years. The number of reports increased each year, with one report in 2018, five in 2019, four in 2020, and eight in 2021. They were caught throughout the year except in January, March, and April, and the months with the most catches were May and November. The research team said, “Since 2017, they have been found not only in Jeju Island but also in a wide range of areas from Geoje, Busan, Yeosu to Busan Gijang, and recently, they have been frequently observed off the coast of Ulsan in the East Sea.”
The research team obtained three blue-ringed octopuses and analyzed the concentration of tetrodotoxin, which was detected at an average of 6.5µg/g throughout the body. The highest concentration was found in the salivary glands, which contained an average of 22.4µg/g. In a safety assessment of food and pharmaceuticals, tetrodotoxin was found to be distributed in the salivary glands at levels ranging from 259.4 to 883.5µg/g. In addition, toxins of 5.1µg/g and 3.6µg/g were detected in the arms and head, respectively, confirming that the blue-ringed octopus is not safe to consume. Tetrodotoxin can cause poisoning if exposed to more than 200µg and can be fatal if exposed to more than 2000µg.
