This predatory species takes a range of marine prey including other echinoderms (sea urchins, starfish and brittlestars), worms and molluscs as well as carrion (3). It often prizes bivalve shells apart, using the suckers on the tube-feet. Once a small gap has been opened, the common starfish inserts the lobes of its stomach inside the shell, and starts to digest the bivalve (2). This starfish has a good sense of smell, which helps it to locate its prey and avoid predators (3). Some of its prey species are able to smell the starfish as it approaches and avoid it (3).
The sexes are separate, breeding occurs in spring and summer and fertilisation occurs externally (2). The early larval stage of the common starfish (called a 'bipinnaria' larva) is planktonic, transforming into a 'brachiolaria' larva before undergoing full metamorphosis and settling around 87 days after fertilisation (3). The life-span of a common starfish is between 5 and 10 years (3). Large aggregations occasionally form, of around 100 individuals per square metre (3). It is not known what triggers these aggregations (3).