Common starfish

Asterias rubens, the common starfish (Asteriidae), has five arms, occasionally four to eight, and a radius usually of 10–30 cm, with a maximum of 52 cm. Four rows of suckered tube feet allow it to crawl and prise open bivalves; once the gap between valves narrows below 0.1 mm it everts its cardiac stomach and digests the prey within the shell. It ranges through the north-eastern Atlantic from Norway to Senegal and the north-western Atlantic from Labrador to the Gulf of Mexico, from the intertidal zone to 650 m. It has not been assessed by IUCN.