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Facts about Blue-ringed Octopus

Kashmira Lad
Although the blue-ringed octopus is rather small in size for the amount of venom it produces, this beautiful and elegant-looking cephalopod is surely not to be taken lightly.

Did You Know?

Blue-ringed octopus has developed a symbiotic relationship with the bacteria that produce the venomous toxins strong enough to kill up to 26 adults at once. The anti-venom for this poison is not developed till date.
Kingdom - Animalia
Phylum - Mollusca
Class - Cephalopoda
Order - Octopoda
Family - Octopodidae
Subfamily - Octopodinae
Genus - Hapalochlaena
A blue-ringed octopus is characterized by its distinguished appearance (when agitated) and its near-perfect camouflages. Being cryptic against its surroundings, it's not always that you encounter an octopus while wading through the azure waters. There are certain qualities that make this octopus different from the rest.


Confirmed species --
» The Greater blue-ringed octopus (Hapalochlaena lunulata)

» Blue-lined octopus (Hapalochlaena fasciata)

» Southern blue-ringed octopus or lesser blue-ringed octopus (Hapalochlaena maculosa)

Debatable --
» Hapalochlaena nierstraszi


» Like all octopuses, blue-ringed octopus is a mollusk, has eight arms, and three hearts. It also has the ability to regenerate a lost arm.

» The average size of this octopus is 5-8 inches and weighs 0.92 oz.
» When at rest, the octopus is light gray to beige having light brown circular blobs or patches. The octopus derives its common name from the iridescent blue color that appears on its rings when it is flustered. The base colors of the individual species are given as follows:

The Greater blue-ringed octopus - dark brown to gray

Blue-lined octopus - charcoal black, brown to slate gray

Southern blue-ringed octopus or lesser blue-ringed octopus - gray to beige with brown patches
» They spend most of their life camouflaged in their nest or crevices of rocks. They achieve this camouflage by using their dermal chromatophore cells.
» The salivary glands of a blue-ringed octopus contain bacteria that produce tetrodotoxin. A single bite can result in the death of a human due to paralysis or cardiac arrest, often within minutes.
» Tetrodotoxin obstructs the sodium channels in the body causing motor damage and reduced supply of oxygen. If not treated immediately, this leads to feeling of nausea, suffocation, paralysis, and cardiac arrest.


» Blue-ringed octopuses hunt mostly during the day feeding on shrimp and crabs including hermit crabs.

Range and Habitat

» Blue-ringed octopuses are found mostly in crevices and cracks of rocks. They also reside in reefs between rubble and bottom of sandy areas.
» The recorded range is given as follows:
The Greater blue-ringed octopus - Northern Australia, Philippines, Indonesia, the Solomon Islands, Papua New Guinea, and even near Sri Lanka (rarely).

Blue-lined octopus - South and southeastern Australia, south of Queensland and New South Wales.

Southern blue-ringed octopus or lesser blue-ringed octopus - temperate waters of south and in waters ranging from southwestern Australia to eastern Victoria.
*Note: The blue-ringed octopus has not yet been evaluated by the IUCN.
Since these cephalopods stay in hiding most of the time, the only way you can protect yourself is by not prodding or provoking them in case you notice any movement. Appearance of the blue rings is always a sign of agitation, so make sure you do not annoy them further by poking them with an object or clicking photographs without prior preparation.