Eleven Armed Seastar, native to Port Phillip

Eleven Armed Seastar

Scientific Name: Coscinaterias muricata

  • Native to Australia
  • Colour brown
  • Round tipped arms, usually 11 arms (maybe less)
  • Large well spaced spines

The Eleven Armed Seastar is native to Port Phillip and is one of the largest seastars found in Victorian waters. It can also be found in other Southern Australian waters. They tend to inhabit rock and sandy areas and have been found in depths up to 150 metres.

Colour can vary depending on location but in the bay the Eleven Armed Seastar tends to be a mottled brown (other places it may be blue, grey, green & even orange). It's length can be up to 25 cm, measured from the centre to the arm tip. Arms may vary in length and often there are less than eleven because of regeneration due to loss or damaged arms. When attacked by a predator (eg. a Triton Conch) that pins down an arm, the Eleven Armed Seastar are known to voluntarily sever their arm to escape. It reproduces by fission system which means that it splits into two to create new individual seastars. It is an invertebrate, that is it has no back bone.

The Eleven Armed Seastar feed on animal matter such as molluscs (eg. mussels), sea urchins and other small seastars. These wonderful creatures have been known to eat young juvenile Northern Pacific Starfish (the Port Phillip pest).

Unfortunately the Eleven Armed Seastar are often mistaken for the Great Barrier Reef's 'Crown of Thorn Starfish' by uneducated fishermen and often left to die on piers. Victorian waters are far too cold for these northern pests.

The Eleven Armed Seastar plays an important role in our marine ecosystem so if you seen one out of the water, please carefully pick it up and return it to the sea.

(Source: Victorian fishing guide 2016, Port Phillip Bay Marine Life & Bay Fish N Trips)