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Octopus tetricus (Family Octopodidae)

Common Sydney Octopus, Gloomy Octopus

Distribution

Distribution:

Eastern Australia from southern Queensland to southern New South Wales. Also found in northern New Zealand (QLD, NSW).

Features:

A large muscular octopus with an armspan that reaches over two metres. The body is oval-shaped and the eyes are large. The arms are long and muscular, the side pairs being the longest and broadest. The longest are around 3 to 4.5 times the body length, each with two rows of suckers. The webs are deep, the side webs being deepest. The colour is generally mottled orange-brown with orange to red faces to the arms. The iris of the eye is often white. The skin has texture of regular round patches separated by dark grooves. Spikes of skin can be raised over the entire body and arms, aiding in camouflage amongst weed or rocks.

Ecology/Way of Life:

This large octopus is very common on rocky reefs and sand habitats including intertidal rock pools. It is mainly active at night feeding on crabs, lobsters and shellfish. It occupies a permanent lair that is recognised by the scatter of fresh-drilled shells around the opening. Larger animals often sit in the mouth of the lair during the day showing the orange arm faces and white eye. The entrance to the lair is sometimes blocked by the octopus holding loose rocks on the suckers to form a brick wall. Shells are collected and returned to the lair where the octopus drills through the shell using its toothed tongue (radula) and acidic saliva.

Adult males have special enlarged suckers on the side arms which are used in displays to court females. Mating consists of males sending a long third right arm to the female and passing sperm packages into her oviducts. He has to be careful as females can eat the males after mating. This is known as sexual cannibalism. Females lay numerous tiny eggs that hatch into transparent young that travel in the plankton before settling down.

A similar octopus occurs in Western Australia where it is treated under the same species name. The two octopuses are separated by thousands of kilometres, being absent from South Australia, Victoria and Tasmania. They may represent two distinct species.

Preferred Image

Interaction with Humans/Threats:

This large octopus is collected as bycatch in trawl and lobster pot fisheries. It is sold for human consumption and as bait. Both the eastern and western forms take a heavy toll on lobster catches by raiding lobster pots, leaving behind the empty lobster shells.

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. 320 pp

Acknowledgments:

Text, map and photograph by Mark Norman, Museum Victoria.

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Images and Multi-media:  
Attached Image  
image/jpeg 193655 bytes Common Sydney Octopus
Attached Image  
image/jpeg 215364 bytes Common Perth Octopus
Distribution Map  
image/jpeg 31645 bytes Distribution of Common Sydney Octopus

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