Eastern Australia from southern Queensland to southern New South Wales (QLD, NSW).Features:
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, the common name comes from the pattern of short lines of blue on the body. The arms and webs show the more typical blue rings. 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 and rubble areas from intertidal reefs to at least 30 m deep. It mainly forages at night but can also be found active in rockpools during the day. Its diet consists mainly of 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.
Mating occurs by males approaching females and climbing on to their bodies. The male then 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. One human fatality has been linked to this species, the death of a 23-year-old man in Sydney. He was handling the octopus out of water, making the octopus display its blue rings by poking it. The octopus bit the arm of this man who died shortly after. 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.Further Reading:
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, map & photographs by Mark Norman, Museum Victoria.Sponsorship welcomed:
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