Fast Facts: The Common Sydney Octopus

  • Cephalopod literally means ‘head foot’ and members of this group, including octopuses, cuttlefishes, squids and nautiluses, have their foot or tentacles connected to their head, not their body.
  • Cephalopods have the most advanced nervous system of all invertebrate animals and are active hunters.
  • They are carnivorous and use their strong beaks to bite into their prey of fishes, crabs and other molluscs, occasionally injecting venom.
  • They have excellent eyesight and can register shapes, textures and colour.
  • To escape from predators such as seals, dolphins and sharks, cephalopods may release an inky screen in the predator’s face and then make a jet-propelled getaway, using jet propulsion. But some octopuses use a truly extreme measure. They sever an arm and leave the wriggling, disembodied tentacle to distract the predator long enough for an escape – better to lose a limb than its life.
  • The immediate and most obvious difference between cephalopods and other molluscs is cephalopods’ apparent lack of a shell. Octopuses have no shell at all, while cuttlefishes have an internal shell and squids have the horny remains of a shell.
  • 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.
  • The octopuses’ fleshy mantle can be used for jet propulsion by sucking in water and squirting it out through the siphon above. Most of the time though, they use their eight suckered arms to creep about over rock surfaces in search of food. If the octopus is in a hurry to get somewhere, they’ll use jet propulsion for fast movement.
  • Most octopuses have relatively short life expectancies and reproduce only once. In fact, it is the act of mating that triggers the onset of death in almost all of them – females stop eating and survive just long enough to brood their eggs, while males slowly deteriorate and die a month or two after. They literally wait their whole life to grow bigger and stronger, so they can mate successfully.
  • A growing octopus faces a stressful existence, being on an almost permanent hunt for food whilst constantly on the lookout for predators. The solution is camouflage, aided by its intelligence, flexibility and incredible colour-changing skin.
  • There are many fascinating types of octopus, which use master mimicry to survive, such as imitating sea creatures, sea plants, or objects. I’ve seen the Common Sydney Octopus mimic many objects, such as rocks and sea plants very successfully.
  • The largest octopus commonly seen in Sydney; the Common Sydney Octopus is typically grey to mottled brown.
  • 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 under a rock ledge.
  • The Common Sydney Octopus is found on intertidal rocky shores and in the ocean. It has been suggested the Common Sydney Octopus is 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.
  • The Common Sydney Octopus is found in New South Wales and is commonly seen during Sydney shore diving, boat diving, freediving and snorkelling. You sometimes don’t even have to go that deep to see one. I’ve seen many octopus in less than 8 metres of water and many times, I’ve even seen them in not even 3 metres of water, on shore diving sites like Bare Island in La Perouse, for example.
  • The Common Sydney Octopus 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.
  • The Common Sydney Octopus is territorial and sits in its home during the day surrounded by shells, rocks and rubble that it has collected to defend its home. Homes can also be recognised by the scatter of freshly drilled shells of its prey.
  • Octopuses are protected and cannot be taken from ocean rock platforms or Sydney Harbour.
  • 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 the Common Sydney Octopus, where the female eats the male after mating. Ok, so not only do they eat their own kind, but they also eat their own mate!

References: and “Life Story” by Rupbert Barrington and Michael Gunton with foreword by David Attenborough.

Published by Karina Teuma Karina Teuma is a Passionate Marine Biology Enthusiast, Environmentalist, Snorkeller, Freediver, Scuba Diver and more.

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