The Blue Ringed octopus looks small and even a little cute……..

The smaller creatures like the Blue Ringed octopus, do not cause many of us to think, while Scuba diving, about the danger they may present. Certainly I am sure, most people think of Sharks and Rays as being the animals to watch out for!

Pause for a moment and consider the Blue Ringed octopus.

It starts life the size of a pea and is fully grown at about the size of a golf ball.

They are skilled at concealing themselves and carry enough poison in their poison sacs to kill up to 25 adults in a very short period of time.

Of course for it to get hold of and poison 25 adults in one ‘sitting’ would involve some kind of furious activity on the part of the little chap!

There are 10 species of Blue Ringed Octopus with two being the most common:

Hapalochlaena maculosa

This is the lareger of the two which grows up to 20cm (8 in) across its extended tentacles.

Hapalochlaena lunulata

The more common and smaller, weighing about 28 grams (1 oz).


They are soft-bodied animals, with a sack-like body and eight arms covered with suckers.

The Blue Ring octopus is usually a pale brown to yellow colour.

Its behaviour patterns are much the same as other octopus, in that it changes colors to suit its surroundings, hiding in holes and crevices in the reef or rocky tidal pools, due to its small size it also secures itself inside empty shells.

The blue rings on its body only show when the animal is threatened forming a warning.
When the Blue Ringed octopus is agitated, the brown patches darken dramatically, and iridescent blue rings or clumps of rings appear and pulsate within the maculae.

Typically 50 to 60 blue rings cover the dorsal and lateral surfaces of the mantle when this happens.

It should be understood that by the time you see the rings it may be too late!

The Blue Ringed octopus have a beak quite similar to a parrot's beak and this one is strong enough to go through a wetsuit….


  • The Blue Ringed octopus male dies after mating and the female then lays between 50-100 eggs guarding them by carrying them under her tentacle until they hatch about 50 days later. The female then dies as she has been unable to eat while she guards her eggs.

  • It is diurnal (active during the day) and feeds on invertebrates and injured or disabled fish.

  • They have three hearts and blue coloured blood.

  • They apparently do not see colour and octopus in general are said to be highly intelligent.

  • They live for up to two years.

Why its dangerous

The bite is relatively painless.

The poison is not injected but is a neuromuscular paralyzing venom with maculotoxin and tetrodotoxin, contained in the octopus's saliva, coming from two glands each as big as its brain.

The poison has no comparison in land based animals and is in two forms, one is used on its main prey, crabs, and is relatively harmless to humans, the other is used as a defence against predators and is deadly to humans. It blocks the nerve conduction and neuromuscular paralysis is followed shortly by death.


  • Onset of nausea.
  • Hazy Vision progressing rapidly into blindness .
  • Loss of sense of touch, speech and the ability to swallow.
  • Within 3 minutes, paralysis sets in and your body goes into respiratory arrest.
  • Though with fixed dilated pupils, the senses of the patients are often intact. The victims are aware but unable to respond

There is no known antidote for the venom and the only way to treat it currently is to conduct heart massage and artificial respiration as long as artificial respiration starts before marked cyanosis and hypotension develops then continues until the poison has passed out of the system – this needs about 24 hours.

The bottom line is:

There is very little chance of survival and the rule of thumb is: DON’T TOUCH IT, OR POKE IT…… you’ll be sorry, at least for a short time.

Where is it found?

The blue-ringed octopus, Hapalochlaena maculosa, is found only in southern Australia, from southern Western Australia to eastern Victoria in tidal rock pools as well as depths up to 50m.

Hapalochlaena lunulata is found anywhere from Northern Australia to Japan, including Papua New Guinea, Solomon Islands, Philippines, and Indonesia and as far west as Sri Lanka at depths up to 20 m.

For more on creatures like the Blue Ringed octopus, click here

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