The blue-ringed octopus has blue blood, three hearts and enough poison to kill 26 humans. The same nerve toxins injected by a blue-ring are found in the flesh of fugu fish - a pricey delicacy beloved by the Japanese. The ingestion of fugu that's not been expertly prepared leads to more hospitalisations than blue-ringed octopus bite. The blue-ringed octopus has only been attributed with causing three known deaths, but there have been no deaths since the 1960s and hospital admissions are exceedingly uncommon.