They’re Highly Toxic
The blue-ringed octopus produces tetrodotoxin, a neurotoxin found in pufferfish. They produce this toxin with a little help from the symbiotic bacteria in their salivary glands and all it takes is 1 milligram to kill a human. Unfortunately, there is no known cure for this venom that’s 1,000 times more lethal than cyanide and can kill within minutes. But they rarely bite humans unless they feel threatened.