Smilasterias irregularis

Irregular seastar
Smilasterias irregularis
Smilasterias irregularis, Port Stephens, NSW, Photo: Tom Davis


Temperate Australasia


Five-armed species with a similar general appearance to Allostichaster polyplax, but with proportionately longer and thinner arms and without the spinelets on the upper surface forming a regular pattern. The colour is generally light pink, mottled with maroon. It is a cryptic species, generally remaining concealed under rock rubble during the day. Its distribution is highly patchy; in some locations it occurs abundantly, but through much of its geographic range the species is absent from apparently suitable areas.


Max Size: 13 cm

Sea Temperature Range: 15.4-25.2°C

Depth: 1-30m

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: Rare (0.7% 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: Solitary (1 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