Allostichaster polyplax

Many-armed seastar
Allostichaster polyplax
Allostichaster polyplax, South Australia, Photo: Graham Edgar
Allostichaster polyplax
Allostichaster polyplax, South Australia, Photo: Graham Edgar
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Allostichaster polyplax
Allostichaster polyplax


Temperate Australasia


Small, long-armed seastar commonly found under rocks. The number of arms is generally eight, but ranges from six to nine, and several of these arms are usually noticeably smaller than others. This species reproduces by dividing asexually as well as by normal sexual means; each half of the original animal grows new arms to replace those lost. Occasionally an animal is found with a single large arm and seven small, recently formed stumps. A related species with five regular arms (Allostichaster regularis) is found from South Australia to southern Queensland.


Max Size: 9 cm

Sea Temperature Range: 10.6-25.5°C

Depth: 0-238m

Habitat Generalization Index: N/A

Also referred to as the SGI (Species Generalisation Index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here.

Conservation and Rarity

IUCN Status: Not Evaluated

Occurrence: Infrequent (1.9% of sites)

Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed

Abundance: Several (6 per transect)

Abundance is calculated as the average number of individuals recorded per RLS transect, where present.

Edit by: GJ Edgar. 2008. Australian Marine Life. New Holland, Sydney