More about the starfish



The starfish is common all along the Swedish west coast. It is found on rocky and stoney substrate as well as on soft bottoms, notably on mussel and oyster banks. Mobility is attained by a unique hydro-vascular system of tube-feet that enable the starfish to move at speeds of between 3-5 metres an hour.

What it eats

The starfish is commonly known for its ability to open large mussels. To open a mussel the starfish places itself over the mussel, rather like an umbrella and places a great number of tube-feet on the two shell halves. An adult starfish using this technique can exert a traction force of 4 kg. It was thought that the starfish secreted a substance that paralysed the mussel, but it appears that traction is enough to open the mussel. It is enough that the shell is opened 1 mm for the starfish to get its stomach into the mussel shell and come into contact with the mussels softer parts, and accordingly break it down.

Can eat alot at one time

Because the starfish everts its stomach and encompasses its prey when it eats, it is able to digest rather large prey. It is able to prey on organisms that have a diameter equal to the length of its arm.
    The starfish has the ability to smell its prey over long distances. A young starfish (radius 3,5 mm) that had recently fallen to the bottom, ate during its first 6 days, 56 small mussels (1,5-3,5 mm long) per day, which equals about 25-30 % of its own weight. As the starfish gets older, its consumption decreases, adults eat about 3-4 % of their body weight daily. It is the young that are most gluttonous and appear in large numbers. During the winter, consumption decreases markedly, and ceases totally at 2-3 °C.

Eating starfish
Common starfish eating.

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What it eats

Can eat alot at one time


When young


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Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson