ASTERIAS RUBEN

Common Starfish

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Common Starfish

 

Description

The common starfish has 5 arms (although individuals may occasionally have just 4 or as many as 6). The colour varies from red to yellowish-brown and more rarely violet. 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.Place a live starfish on a wet surface, it will quickly attach itself to it using its strong suction cups. Try removing it, it won't be easy. It can even break open mussels with these strong suctions. Starfish use seawater to steer the feet. A smooth spot on top of the starfish is for filtering water. Its anus is also on top, precisely in the middle. Its mouth is exactly opposite, on the underside of the body.

This predatory species takes a range of marine prey including other echinoderms (sea urchins, starfish and brittlestars), worms and molluscs as well as carrion. 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. This starfish has a good sense of smell, which helps it to locate its prey and avoid predators. Some of its prey species are able to smell the starfish as it approaches and avoid it. The sexes are separate, breeding occurs in spring and summer and fertilisation occurs externally. 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. The life-span of a common starfish is between 5 and 10 years. Large aggregations occasionally form, of around 100 individuals per square metre. It is not known what triggers these aggregations.

 

Geography

The Asterias rubens settles in the Northern Atlantic region on rocky, temperate shores. Most sea stars, including the Asterias rubens, may live in a variety of depths, including shallow shores to up to 200 fathoms.

 

 

 

 

Ecosystem

Settlement of the Asterias rubens occurs along the rocky shores of the Atlantic Ocean. Studies performed along the coast of Nova Scotia show the tendency of these starfish to be found in kelp beds; they were the only echinoderms found on the kelp fronds. Further studies have shown that the population density of the Asterias rubens is correlated with subtidal blue mussel, Mytilus edulis, beds. These Mytilus edulis beds are short-lived due to intense predation; therefore, this influences the location of the Asterias rubens. (Barbeau, et al 1996)

Conservation

No special concervation status.

 

Threats

Not currently threatened.

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