Small Cushion Star

Asterina phylactica is a pentagonal starfish with short blunt arms and a flattened shape. It grows to a diameter of about 15 mm (0.6 in) and is olive-green with a central brown star-shaped marking, a pale underside, and a clear cut edge between the upper and lower surfaces. It can be distinguished from the closely related Asterina gibbosa by the fact that it has fewer plates surrounding its mouth, its smaller size and its characteristic colouring. At one time the two were believed to be the same species but it was realised in 1979 that besides the differences in appearance, the two occupied different ecological niches and had different reproductive methods.

Asterina phylactica is native to the northwestern Atlantic, the Mediterranean and Adriatic Seas. Around the British Isles, Asterina phylactica is found around the south-west coasts but also occurs on the west coasts of Scotland and north-west Ireland. In Wales, the typical habitat for this species is rock pools on exposed coasts with much encrusting coralline algae. It is a tolerant species and able to adapt to a range of different salinities and temperatures.