Why is the blue-ringed octopus dangerous?
The blue-ringed octopus is dangerous because its saliva contains tetrodotoxin, a powerful nerve toxin that can paralyse and kill a person. Its bite is often painless, so victims may not notice it.
Blue-ringed octopuses are small, usually no bigger than a golf ball with arms spread to about 20 centimetres. They live in rock pools, reefs and shallow coastal waters around Australia, including near Sydney, Melbourne and Perth.
When calm, they are pale yellow-brown and well camouflaged. When threatened, they flash bright blue rings as a warning. Most bites occur when people pick them up from rock pools or step on them.
First aid
Tetrodotoxin blocks nerve signals, causing numbness, weakness and paralysis, including the muscles used for breathing. There is no antivenom, but victims can survive if they receive rescue breathing and hospital support until the toxin wears off.
If someone is bitten, apply a pressure immobilisation bandage, call an ambulance and be ready to start CPR.
The octopuses use their toxin to hunt crabs and shrimp. Despite their reputation, deaths are very rare, and the animals are shy. The simplest rule is never to touch or pick one up.
Did You Know?
The tetrodotoxin in blue-ringed octopuses is made by bacteria living in their salivary glands.