Greater blue-ringed octopus
The greater blue-ringed octopus is a small sea creature that lives in the warm shallow waters of the Indo-West Pacific, including around Australia. It is one of the most venomous marine animals in the world, so knowing what it looks like matters.1
🔍 How to recognise it
- A small octopus, up to 10 cm with its arms included, weighing about 80 grams on average.1
- Electric blue rings, about 7 to 8 mm across, roughly 60 of them, spread over its whole skin.1
- The rings flash iridescent blue as a warning signal, each flash lasting about a third of a second.1
- Its body colour varies from yellow ochre to light brown, or whitish when inactive.1
- Blue lines run through its eyes.1
Venom power
Venom comes out through its fangs or teeth when it bites.
What does its venom do?
Its venom contains tetrodotoxin (TTX), a powerful neurotoxin, which is a poison that attacks the nerves. It paralyses the muscles needed for movement, and in people it can lead to death through respiratory paralysis, which means the breathing muscles stop working. Symptoms include tingling and numbness of the face and lips, sweating, severe headaches, dizziness, speech problems, weakness and vomiting. Symptoms can appear between 15 minutes and four hours after a bite, and the victim stays conscious throughout.1
How dangerous is it to people?
Danger to people: DeadlyOne of the most dangerous animals in the world.The bite is capable of being fatal to humans. The text says the bite is painless, so a person may not notice it. Children are more sensitive to the toxin. Death can occur between 20 minutes and 24 hours after symptoms begin.1
What does it do when it is scared?
It flashes its blue rings as a warning to predators, and it uses its venom to defend itself.1
🚑 If it bites or stings
- Pressure immobilisation: wrap a firm elastic bandage over the bite and then up the whole limb, splint it, and keep the person completely still until help arrives.
- A blue-ringed octopus or cone snail can stop a person breathing while they are still awake: call for help and be ready to give rescue breaths until the ambulance takes over.
Always call your emergency number first (112, 000, 911). This is general first aid guidance, not medical advice. First aid basics
⛑️ Stay safe
- Never touch, catch or tease a wild animal, even a small one, and even if it looks asleep or dead.
- Give it space. If you meet one, stay calm, step back slowly and let it go its own way.
- If one bites or stings you: stay calm, keep still, call your emergency number (112, 000, 911) or get to a hospital fast. Remember what it looked like, a photo helps.
It is not out to get you. It uses its venom to catch food or to protect itself, and it would much rather hide. More about staying safe
Where in the world?
How big is it?
How long is it?
How big is Greater blue-ringed octopus compared to YOU?
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How fast is it?
Facts
The greater blue-ringed octopus is one of the most venomous marine animals in the world, despite being small.1
Its venom contains tetrodotoxin, the same toxin found in pufferfish.1
There is no known antidote or antitoxin for tetrodotoxin, and the toxin does not break down when heated or boiled.1
Its blue rings are a warning signal to predators, showing that it is highly venomous.1
Males die after mating, and females die after guarding their eggs because they refuse to eat.1
Myth buster
Myth: A small octopus is harmless.
Truth: Despite its small size, its bite can be deadly to humans.1
For venom experts
- Scientific name
- Hapalochlaena lunulata
- Group
- Cone snails & octopuses
- Also called
- Blue-ringed Octopus1
- Family
- Octopodidae2
- Order
- Octopoda
- Continents
- The oceans
- Babies
- The female lays 50 to 100 eggs, which she carries under her arms for about a month. The young hatch as tiny planktonic paralarvae, about the size of a pea.1
- Lifespan
- about 2 years1
- Danger to people
- 5 / 5: Deadly3
Where the facts come from
- Greater blue-ringed octopus (Wikipedia (CC BY-SA 4.0))
- Hapalochlaena lunulata (iNaturalist): names and classification.
- Venom Wiki: the danger level, the typical size and the speed guess are our own. See how we work them out: How we rate danger.
Every fact on this page has a number that points to its source. If we got something wrong, sorry, we are animal fans, not a science journal. Tell us at [email protected] and we will fix it.
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Geography cone
Southern blue-ringed octopus
Blue sea dragon
Common octopus
Giant Pacific octopus
Blue-lined octopus
Australian box jellyfish
Japanese pufferfish
Hawksbill sea turtle
Irukandji jellyfish
Reef stonefish
Crown-of-thorns starfish