Common starfish  (Asterias rubens)

Widespread in Britain (3).

The common starfish has 5 arms (although individuals may occasionally have just 4 or as many as 6) (2). The colour 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).

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). It 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 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 (called a 'bipinnaria' larva) is planktonic, it transforms 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).

Not currently threatened.

Conservation action has not been targeted at this species.

For more on this species see the Marine Life Information Network (MarLIN) species account, available from:
http://www.marlin.ac.uk/species/Asteriasrubens.htm

• Larval: of the stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
• Metamorphosis: an abrupt physical change from the larval to the adult form.
• Planktonic: aquatic organisms that drift with water movements; may be either phytoplankton (plants), or zooplankton (animals).

1. National Biodiversity Network Species Dictionary (January, 2003)
   http://www.nhm.ac.uk/nbn/
2. Fish, J.D. and Fish, S. (1996) A student's guide to the seashore. Second Edition.Cambridge University Press, Cambridge.
3. Budd, G., 2001. Asterias rubens. Common starfish. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. (August, 2002)
   http://www.marlin.ac.uk/species/Asteriasrubens.htm