Blue-ringed octopus

This unassuming, shy little octopus is lauded as one of the most lethal creatures of the sea. We’ll reveal how to spot one, why they turn blue, and what to do if bitten. And you might want to find that out, because the salivary glands of one individual octopus could contain enough venom to paralyse ten men. To find out more, read on.

What does it look like?

Measuring 12 - 20cm across its stretched tentacles, the Hapalochlaena lunulata, or greater blue-ringed octopus, is a small sea creature weighing between 25 - 80g. There are more than one species of this octopus, but the Hapalochlaena lunulata is the most prevalent in Tropical North Queensland.

When resting, the octopus will look dark brown and yellow. And while they may look harmless and certainly aren’t actively aggressive, the blue-ringed octopus is highly venomous, with a bite that is poisonous to humans, resulting in paralysis and possibly cardiac failure.

Is it always blue?

No, it will only turn blue when provoked. The body will darken and its 50 – 60 rings will glow an electric blue. This is when it is most likely to bite, using its two beak-like jaws to release a toxin from its salivary glands known as tetrodotoxin, also found in the flesh of the pufferfish. The beak of the octopus is located on the underside of the middle of the body.

Where do they live?

A reclusive creature, rarely seen in water deeper than 10ft, this little cephalod (octopus) lives in shallow reef waters, at the bottom of coral rock pools, and under shells.

Are they only found in Queensland?

No, they are found in the tropical and subtropical waters of Sri Lanka, the Philippines, other areas of Australia, and south Japan.

What should I do if I see one?

If you see one, do not touch, as there is no known antidote.

What is the likelihood of being bitten by one?

Most incidents of bites occur through accidental handling. One of the biggest dangers are with small children who are attracted to the bright colours of the octopus.

What are the symptoms of a bite?

  • Most bites will cause minimal pain initially, but after approximately five minutes the bite will begin to throb and may cause the extremity bitten to go numb.
  • Bleeding from the bite may occur, as well as nausea, vomiting, change in vision, numbness of the lips, tongue and mouth, and difficulty swallowing, seeing, and speaking.
  • After approximately 10 minutes the victim may have difficulty breathing, becoming paralysed and requiring artificial ventilation.
  • If medical care is not provided immediately, respiratory failure may occur, which could lead to cardiac arrest. 

How do you treat a bite?

  • Dial 000 for medical assistance as it is critical help is sought immediately.
  • Try to keep the bite victim as calm as possible, keeping them still.
  • Apply pressure to the wound with a firm bandage.
  • If the patient is having trouble breathing, prolonged CPR will be required until medical attention is received. Otherwise, the victim may fall unconscious and die from lack of oxygen.

What else can you tell me about this small but dangerous creature?

The female lays approximately 100 - 200 eggs. They are firm and capsule-like, and the female guards the eggs at all times. She carries her eggs in a cluster under her tentacles. Once the eggs have hatched after 3 - 6 months, the female dies. This is because the female stops eating while looking after her eggs. Now that’s commitment!

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