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Reef starfish (Stichaster australis) is a species of starfish found in the South Pacific Ocean around New Zealand. A keystone species, this carnivorous starfish plays an important role in local biodiversity by reducing the size and spread of mussel populations.

Reef starfish
Starfish orgy (Stichaster australis).jpg
Scientific classification
S. australis
Binomial name
Stichaster australis
(Verrill, 1871)



S. australis is pink or purple in colour, occasionally orange,[1] with 11 arms although rare individuals have 10 or 12.[2]

Ecological impactEdit

S. australis rising from the rock near Auckland

Found throughout New Zealand, S. australis is a keystone species in both the North and South Islands, playing an important role in mussel predation.[2][3] In one study on the west coast of the South Island conducted in the 1970s, S. australis was found to have removed a majority of transplanted mussels within two or three months of their placement, while the mussels expanded within six months to cover 20-30% of the low zone when S. australis was removed.[3] Without their predation, the mussels overwhelmed the area, threatening biodiversity.[4][5]

The juveniles of the species are detritivores.[6]


  1. ^ Miller, Michael; Gary Batt (1 January 1973). Reef and Beach Life of New Zealand. Collins. p. 25.
  2. ^ a b Dorfman, Eric (25 April 2006). Sanctuary: New Zealand's Spectacular Nature Reserves. Penguin. p. 28. ISBN 978-0-14-301993-0. Retrieved 29 April 2011.
  3. ^ a b Kareiva, Peter M.; Simon A. Levin (2003). The importance of species: perspectives on expendability and triage. Princeton University Press. p. 29. ISBN 978-0-691-09005-4.
  4. ^ Bayne, Brian Leicester (1976). Marine Mussels, their Ecology and Physiology. Cambridge University Press. p. 54. ISBN 978-0-521-21058-4. Retrieved 29 April 2011.
  5. ^ British Ecological Society (1980). The Journal of Animal Ecology. Blackwell Scientific Publ. p. 674. I have removed a starfish, Stichaster australis Verrill, from an intertidal shoreline in New Zealand, producing rapid domination by a mussel (Perna) at the expense of other resident-space-requiring species (Paine 1971).
  6. ^ Morton, Brian (1993). The marine biology of the South China Sea: proceedings of the First International Conference on the Marine Biology of Hong Kong and the South China Sea, Hong Kong, 28 October-3 November 1990. Hong Kong University Press. p. 369. ISBN 978-962-209-355-3.

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