An initiative of Earthwatch Institute

  1. Pin_cushion_seastar_by_al_burberry Up to 20mm in diameter by AL Burberry

Pin-cushion Seastar

Parvulastra exigua


  • Five-armed seastars normally have five arms (some can be found with six) that are webbed or joined by skin which radiate out symmetrically from a central disc, giving them a pentagon-shaped appearance. 
  • They are usually grey-blue, grey-green, olive or khaki green in colour, with a paler version of the colour on their underside (ventral side).
  • Size:  up to 20mm in diameter

What to Observe

Search area for 30 minutes and record under the following categories:

  • Abundant - found easily with little searching
  • Frequent - found with minimal searching
  • Rare -  only 1 or 2 individuals found with intensive searching
  • Not found - not present during search

ClimateWatch Science Advisor

As a result of climate change, warm tropical ocean currents are expected to strengthen and persist for longer periods in southern coastal area normally dominated by cooler waters. The consequent increases in water temperature are likely to result in unfavourable growing conditions for seastars. 

When To Look

Throughout the year.

Where To Look

  • Common on rocky shores, from mid to high tide levels. Usually found in rock pools, crevices and wet areas, often near Neptune’s necklace (Hormosira banksii).
  • Port Lincoln SA, TAS, VIC, up to Northern NSW. 


Davey, K. (1998). A Photographic Guide to Seashore Life of Australia. New Holland Publishers Australia Pty Ltd.

Edger, GJ. (2008). Australian Marine Life. The Plants and Animals of Temperate Waters [2nd Ed]. New Holland Publishers Australia Pty Ltd.



  1. Search Species

  1. What Else?

    The pentagon shape distinguishes the five arm sea star from most other seastars in the intertidal areas, with the exception of Meridiastra species which can look similar. Meridiastra species have six arms and are only occasionally found amongst low tide rock around the southern coastline Australia.  

  1. Did You Know?

    Five-armed seastar are hermaphrodites, which means they have both male and female sexes.

    They lay their eggs on the rock platform unlike the other seastars which produce swimming larvae.