Southern Blue-ringed Octopus
Southern Australia from Victoria and Tasmania to southern Western Australia (VIC, TAS, SA, WA).
A small muscular octopus with an armspan of up to 20 cm. The body is oval in shape often with an extended pointed tip at the rear. The eight arms have two rows of suckers, none of which are enlarged. The webs are fairly deep. The most distinctive feature of these small octopuses is the patterns of brilliant iridescent blue markings over the body, head and arms. In this species, small blue rings are scattered over the body, arms and webs. These octopuses can also do excellent camouflage, hiding the blue markings. The skin can push up small bumps and spikes to aid in camouflage.
Ecology/Way of Life:
This small octopus lives in shallow coastal waters on rocky reefs, rubble areas and seagrass meadows from intertidal reefs to at least 50 m deep. It mainly forages at night mainly feeding on crustaceans, particularly crabs. As in all blue-ringed octopuses, this species has large salivary glands that produce very strong toxins. It is thought that the toxins are produced by symbiotic bacteria that live in the salivary glands. The toxins are used to quickly paralyse their crab prey but also act as a good defense against attackers. The brilliant blue displays warn potential predators to keep away.
This species of blue-ringed octopus has lost the ability to produce ink. It is possible that the strong toxins are enough to protect this octopus. Other members of the group can still produce ink.
Mating occurs by males approaching females and climbing on to their bodies. Where animals occur in larger numbers several males can attempt to mate at the same time causing a female to walk around with several males in a row hanging off her body. The male inserts his third right arm into the female's gill cavity and passes sperm packets into her oviducts. The female lays the large eggs in strings and carries them with her in her webs, rather than attaching them to rocks or shells. The large young hatch with full colour patterns and immediately settle to the seafloor.
Interaction with Humans/Threats:
These small octopuses pose a direct threat to humans. No human fatality has been linked to this species, but several biting incidents caused serious paralysis in the victims who may have died if they had not received immediate first aid. In one case, a fisherman accidentally sucked an octopus into his flooded gumboot and unwittingly squashed the animal until it bit. The saliva of this octopus contains the powerful neurotoxin, tetrodotoxin, the same toxin that is found in pufferfishes. It acts by blocking muscle action causing the victim to suffocate due to the inability to breath. In any suspected case of blue-ringed octopus bite, apply mouth-to-mouth resuscitation if breathing stops. The heart generally continues to function and the patient is conscious and aware of his surroundings. To be safe, people should avoid handling any small octopuses. The only human harvest of these octopuses is for aquariums.
Norman, M.D. and A. Reid. 2000. A guide to the squid, cuttlefishes and octopuses of Australasia. Gould League/CSIRO Publishing, Melbourne. 96 pp.
Norman, M.D. 2000. Cephalopods: A world guide. ConchBooks, Hackenheim, Germany.
Text and photographs by Mark Norman, Museum Victoria.
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|Images and Multi-media:|
|Warning colour pattern of poisonous Southern Blue-ringed Octopus|
|Distribution of Southern Blue-ringed Octopus|