Description

 A small starfish (up to 5 cm) with 5 (rarely 4 or 6) very short, broad-based arms. Upper surface covered with groups of short stiff spines. Colour variable but usually brown, green or orange; mottled individuals are present in some populations. The predominant colour pattern varies from area to area and with habitat, specimens from lower shore situations generally being paler in colour.Asterina gibbosa is a protandrous hermaphrodite: small or young individuals are males but as they become older and increase in size they develop into females. Asterina gibbosa may be distinguished from the morphologically similar Asterina phylactica which has a consistent colour pattern with a brown central star typically overlying the general background colour. There are rarely spines on the mouth plates of Asterina phylactica.