Small Cushion Star

Asterina phylactica

Asterina phylactica is a small sea star characterized by its pentagonal shape and short, blunt arms. It typically grows to about 1.5 cm in diameter and displays an olive-green coloration with a distinct central brown star-shaped marking. The underside is pale, and there is a clear demarcation between the upper and lower surfaces. This species can be distinguished from the similar Asterina gibbosa by its smaller size and fewer plates surrounding its mouth. Both species were once thought to be the same, but they occupy different ecological niches and have different reproductive strategies. This starfish is found in various locations around the British Isles, particularly along the south-west coasts and the west coasts of Scotland and north-west Ireland. It inhabits rock pools on exposed coasts, often associated with encrusting coralline algae. Asterina phylactica is a tolerant species, capable of adapting to a range of salinities and temperatures, typically residing at depths of 0 to 2 meters. Feeding primarily on the film of bacteria and diatoms on rock surfaces, Asterina phylactica everts its stomach to digest its food externally. In its first year, this species is male, transitioning to hermaphroditism in the following year, where it produces both sperm and eggs. Breeding occurs in late spring, with individuals gathering to release sperm into the sea, where fertilization takes place. The developing embryos are brooded under the starfish for about three weeks before they emerge as juvenile starfish. While the conservation status of Asterina phylactica has not been evaluated, it is recorded in various marine environments, indicating its presence in different habitats.