Common Sydney Octopus

Introduction

The distinctive white eye pupil and orange-rust red arms of this octopus species is often the first thing you notice as they emerge from their lairs under rock ledges.

Identification

Octopus tetricus is typically grey to mottled brown with orange-rust red arm faces that taper to the tip. The eyes are usually white, and its skin consists of many small pavement-like patches and large papillae which can be raised over the body to produce a spiked appearance, common when imitating seaweed.

Habitat

The Common Sydney Octopus is found on intertidal rocky shores and in the ocean. It has been suggested Octopus tetricus are associated more commonly with rocky reef habitats during the breeding season, but tend to spend a considerable portion of their life in soft-sediment habitats.

Distribution

O. tetricus is found throughout Subtropical eastern Australia and northern New Zealand, including Lord Howe Island. A closely-related species or subspecies occurs at similar latitudes in Western Australia.

Feeding and diet

O. tetricus primarily emerges at night to feed, using its sharp beak to feed on crabs and molluscs, such as snails and bivalves. It has been known to feed on its own species.

Other behaviours and adaptations

It can change the colour of its skin (normally mottled brown) and shape to imitate seaweed.

Octopus tetricus is territorial and sits in its lair during the day surrounded by rocks and rubble that it has collected to defend its home. Lairs can also be recognised by the scatter of freshly drilled shells of its prey.

Most of the time O. tetricus use their arms to creep about rock surfaces but it can also use jet propulsion for fast movement.

Breeding behaviours

Females produce numerous small eggs (1-2mm) that it attaches in strings to the roof of rock crevices, which hatch into planktonic young. Sexual cannibalism has been observed in Octopus tetricus, where the female eats the male after mating.

Economic impacts

May be caught as bycatch in trawl and lobster-pot fisheries and sold for both human consumption and bait.

References

• Norman, M., (2000) Cephalopods- A World Guide, ConchBooks, Germany (Hackenheim)
• Norman, M & A. Reid., (2000) A Guide to Squid, Cuttlefish and Octopuses of Australasia, CSIRO Publishing, Victoria (Collingwood)
• Anderson, Tara, J. (1997) Habitat selection and shelter use by Octopus tetricus, Marine Ecology Progress Series, (150): 137-148.