Common starfish  (Asterias rubens)

The common starfish is widespread in Britain (3).

The common starfish (Asterias rubens) has five arms (although individuals may occasionally have just four or as many as six) (2). The colour of the common starfish varies from red to yellowish-brown and more rarely violet (2). The upper surfaces of the arms feature a row of spines along the centre, and the underside has rows of 'tube-feet', which have suckers at the tips (2).

The common starfish is common and widespread around the coasts of Britain and Ireland, and throughout the northeast Atlantic from Norway to Senegal (3).

Found on a range of marine substrata including fine sand, rock and gravel (3). The common starfish can often be found amongst mussel beds and barnacles on British shores (2).

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).

The common starfish is not currently threatened.

Conservation action has not been targeted at the common starfish.

For more on the common starfish, see:

• Marine Life Information Network (MarLIN) - Common Starfish, Asterias rubens:
  http://www.marlin.ac.uk/species/Asteriasrubens.htm