Southern blue-ringed octopus (Hapalochlaena maculosa)
|Also known as:||lesser blue-ringed octopus|
|Size||Typical arm span: less than 15 cm (2)|
Average weight: 38 g (3)
- The southern blue-ringed octopus is named for the small, iridescent blue spots it develops when alarmed.
- The southern blue-ringed octopus is one of the world’s deadliest venomous animals, although it is not normally aggressive towards humans.
- The toxin in the southern blue-ringed octopus’s venom is 1,000 times more powerful than cyanide.
- The female southern blue-ringed octopus carries its eggs until they hatch, and dies shortly afterwards.
The southern blue-ringed octopus has yet to be classified by the IUCN.
The southern blue-ringed octopus (Hapalochlaena maculosa) is one of three closely related species belonging to the genus Hapalochlaena (4). Despite its small size, it is considered to be one of the world’s deadliest venomous animals (3).
The upper surface of the southern blue-ringed octopus has a rough texture and is covered in wrinkles. At rest, this species is well camouflaged, being grey to beige with light brown patches on the body and arms (3). However, when the octopus is disturbed or threatened, special pigment cells in the skin called ‘chromatophores’ become activated to display as many as 60 iridescent blue rings on the mantle and arms, which act as a warning signal (2) (3) (5). It is these blue rings which give the southern blue-ringed octopus its common name (4).
The range of the southern blue-ringed octopus extends across the entire south coast of Australia (6), from Western Australia to eastern Victoria (3).
Like other blue-ringed octopuses, the southern blue-ringed octopus is often sighted in coastal waters at depths of up to 50 metres. Members of this genus are commonly found in shallow pools, under rocks and corals, or among clumps of sea squirts, particularly after storms. These soft-bodied animals often conceal themselves within crevices, seashells or coral rubble for protection (3).
The life cycle of the southern blue-ringed octopus, from mating through to the eggs hatching and the young reaching maturity, lasts for approximately seven months. The eggs are carried by the female throughout their development, which lasts for around two months, and the female does not eat during this time. Once hatched, the young grow rapidly and begin hunting live prey within one month (6). Young southern blue-ringed octopuses are thought to be venomous from birth (2), and their blue rings appear when they are about six weeks old (6).
This species reaches sexual maturity at just four months old (3) (6), and may begin laying eggs a month after that. The adult female southern blue-ringed octopus dies shortly after the eggs have hatched (6), and both sexes are unlikely to live for more than one year (3).
Like all cephalopods, the southern blue-ringed octopus is an active predator (2). This species is equipped with powerful venom which is secreted from the posterior salivary glands and is used to immobilise and kill the octopus’s prey of crabs and other crustaceans (2) (3) (6). The southern blue-ringed octopus may also consume small fish (2) (3).
Despite the southern blue-ringed octopus’s small size, its bites have been known to cause human fatalities (3) (5) (7), and the soft tissues of this species are also extremely poisonous if consumed (4). There is no antidote to the octopus’s venom (3) (5), but this species is not generally aggressive, preferring to hide rather than confront a potential attacker (2) (3).
Like other cephalopods, the southern blue-ringed octopus is considered to be one of the most intelligent of all invertebrates (2) (8).
Little information is available on the potential threats to the southern blue-ringed octopus. However, members of its genus are sometimes collected for the aquarium trade, despite the risk posed by their venomous bite. The habitats these species occupy are also being degraded and fragmented by human activities, and blue-ringed octopuses may potentially be affected by overfishing and by human disturbance in the form of divers, tourists and beach-goers (3).
There are currently no known conservation measures in place for the southern blue-ringed octopus. However, any conservation efforts for this and other blue-ringed octopus species would also benefit other marine species with which they share their habitat. The southern blue-ringed octopus is likely to play an important role in its ecosystem, and might also help to control invasive crustaceans in parts of its range. In addition, its venom could have potential medical uses (3).
Suggested conservation actions for the southern blue-ringed octopus and other blue-ringed octopus species include increasing the size of Marine Protected Areas and enforcing laws to reduce run-off of pollutants into coastal waters. It will also be important to educate the public, not only on the dangers posed by these species, but also on the important role they play in the marine environment. More information is needed on the populations of this small octopus, and measures to regulate its export for the aquarium trade should also be considered (3).
Find out more about the southern blue-ringed octopus and other blue-ringed octopus species:
MarineBio - Blue-ringed octopuses:
More information on marine conservation in Australia:
Australian Marine Conservation Society:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
- Cephalopod: from the Greek for ‘head-foot’, a class of molluscs that occur only in marine habitats. All species have grasping tentacles, and either an internal or external shell. Includes nautiloids, cuttlefish, squids, octopuses, and extinct ammonites and belemnites.
- Crustaceans: diverse group of animals with jointed limbs and a hard chitinous exoskeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Gland: an organ that makes and secretes substances used by the body.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Mantle: in molluscs, a fold of skin that encloses a space known as the mantle cavity, which contains the gills. The mantle is responsible for the secretion of the shell.
Integrated Taxonomic Information System (ITIS) (July, 2013)
- Norman, M. and Reid, A. (2000) A Guide to Squid, Cuttlefish and Octopuses of Australasia. CSIRO Publishing, Collingwood, Australia.
Lambert, W.A. (2011) A Review of Blue-Ringed Octopus Conservation. M.A. Thesis, Prescott College, Arizona. Available at:
- Kim, J.H., Suzuki, T., Shim, K.B. and Oh, E.G. (2012) The widespread distribution of the venomous and poisonous blue-lined octopus Hapalochlaena spp., in the East/Japan Sea: possible effects of sea warming. Fisheries and Aquatic Sciences, 15(1): 1-8.
- Nimorakiotakis, B. and Winkel, K.D. (2003) Marine envenomations. Part 2 - Other marine envenomations. Australian Family Physician, 32(12): 975-979.
- Tranter, D.J. and Augustine, O. (1973) Observations on the life history of the blue-ringed octopus Hapalochlaena maculosa. Marine Biology, 18(2): 115-128.
- Williams, B.L. (2010) Behavioral and chemical ecology of marine organisms with respect to tetrodotoxin. Marine Drugs, 8: 381-398.
- Mather, J.A. (2012) Cephalopod intelligence. In: Vonk, J. and Shackelford, T.K. (Eds.) The Oxford Handbook of Comparative Evolutionary Psychology. Oxford University Press, Oxford.