Southern Octopus, Hammer Octopus
Eastern Australia from southern Queensland to southern New South Wales (QLD, NSW).
A moderate-sized muscular octopus with an armspan that reaches around 40 cm. The body is oval in shape and is rimmed around the sides by a raised skin ridge. The arms are around 3-4 times the body length, each with two rows of suckers. The webs are deep, particularly between the side arms. The colour is generally sandy brown with a scattering of small black and white spots. There is a peanut-shaped white patch on the head between the eyes. The skin is covered in regular small low bumps and horns can be raised above the eyes.
Ecology/Way of Life:
This octopus lives on sand and mud substrates in coastal waters to depths of at least 134 m. It emerges at night to forage over the sand for crabs and other crustaceans. During the day it buries in the sand or hides in shells or human refuse (such as bottles). The ridge of skin around the edge of the body is also found in other octopuses that bury in the sand. It may aid in gliding the octopus under the sand when it buries. This octopus buries close to the sand surface so that it can still draw clean water in to its gill cavity in order to gain oxygen. When alarmed this octopus darkens the skin around the eyes to give the appearance of a head of a larger animal.
The common name of this octopus comes from the modified arm tip on the third right arm of adult males. This tip is a large swollen club that is used to pass sperm packages in to the female's oviducts during mating. Its large size may mean it is used in courtship displays or may be used to scoop the sperm of previous suitors out of the female's oviducts. Females lay large single eggs that are attached singly to hard surfaces such as shells. The large eggs would hatch into bottom-living juveniles.
Interaction with Humans/Threats:
This octopus is caught in low quantities as bycatch in commercial trawls. It is sold for human consumption and as bait.
Stranks, T. and M.D. Norman. 1992. Review of the Octopus australis complex (Cephalopoda: Octopodidae) and description of a new species. Memoirs of the Museum of Victoria, 53(2): 345-373.
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 by Mark Norman; photographs by David Paul.
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|Images and Multi-media:|
|Hammer Octopus showing the ridge of skin around the edge of the body|
|Swollen modified arm tip of adult male Hammer Octopus|
|Distribution of Hammer Octopus|