The Upside Down Under
A deadly blue-ringed octopus


What has 8 legs, 3 hearts and enough venom to kill 26 scuba divers? The blue-ringed octopus, one of Australia's many deadly animal attractions!

The blue-ringed octopus is recognized as one of the world's most venomous marine animals. Despite their small size—12 to 20 cm (5 to 8 in)—and relatively docile nature, they are dangerous to humans if provoked and handled because of their venom which contains the powerful neurotoxin tetrodotoxin. (more on that later)

Blu-ringed octopus

They can be identified by their yellowish skin and characteristic blue and black rings that change color dramatically when threatened. They eat small animals, including crabs, hermit crabs, shrimp, and other crustaceans.

If they are provoked, they quickly change color, becoming bright yellow with each of the 50-60 rings flashing bright iridescent blue within a third of a second as a warning display.

Blue-Ringed Octopus

A Venomous Cocktail

The octopus produces venomous cocktail  that contains tetrodotoxin, 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine.

The major neurotoxin, a component of its venom was originally known as maculotoxin but was later found to be identical to tetrodotoxin, a neurotoxin which is also found in pufferfish that is 10,000 times more toxic than cyanide.  The toxin is produced by bacteria in the salivary glands of the octopus and is more violent than any found in land animals.

Tetrodotoxin blocks sodium channels, causing motor paralysis and respiratory arrest within minutes of exposure, leading to cardiac arrest due to a lack of oxygen.  The nerve conduction is blocked and neuromuscular paralysis is followed by death.

Dangers of the blue-ringed octopus
There is no blue-ringed octopus antivenom available.

Even though they might seem like a cute little creature, be warned that they have a beak that can penetrate a wet-suit and inject a poison that is powerful enough to kill an adult in just under minutes. As there is no known antidote to save you, the only treatment is hours of heart massage and artificial respiration until the poison has worked its way out of your system.

Blue-Ringed Octopus
It may look cute but the blue-ringed octopus can kill you in just minutes!

Symptoms of a blue-ringed octopus bite

  • Onset of nausea
  • Hazy Vision. (Within seconds you are blind.)
  • Loss of sense of touch, speech and the ability to swallow
  • Within 3 minutes, paralysis sets in and your body goes into respiratory arrest.


Figure 1 attribution: By Roy Caldwell - Huffard CL, Caldwell RL, DeLoach N, Gentry DW, Humann P, B. MacDonald, B. Moore, R. Ross, T. Uno, S. Wong. 2008. Individually Unique Body Color Patterns in Octopus (Wunderpus photogenicus) Allow for Photoidentification. PLoS ONE 3(11): e3732., CC BY 2.5,

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