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May 10, 2013

Meet the Spiny Seastar

© OCEANA Sergio Gosálvez


We thought it was high time to bring back a Friday tradition we started a while ago, to introduce our readers to some interesting sea creatures. This week, we are featuring the spiny sea star (Marthaasterias glacialis).

Sea stars belong to the Echinodermata phylum, which also includes sea urchins, sea cucumbers and brittle stars. Most sea stars typically have five rays or arms, which radiate from a central disc. The spiny sea star is large, reaching up to 70 cm across, but is more commonly found at 25-30 cm. It has 5 narrow arms, each boasting 3 rows of spines, which are white, and usually with purple tips. Its color can range from brown to pale greyish green.

The spiny sea star can be found in a variety of habitats, from sheltered muddy areas to wave-exposed rock facades,  and at depths that range from extremely shallow down to about 200 m.

It voraciously feeds on various animals, dead or alive, such as mollusks, shellfish or fish, which can cause damage in mussel and oyster farms.

Sea star populations can grow very quickly because of their ability to regenerate limbs that have been cut off from their bodies. Regularly caught in nets, they are often torn to pieces and thrown back to sea by fishermen firmly believing that the sea stars would die, when in reality they were just creating more of them. While many sea stars have the ability to regenerate lost arms so long as the central disc is attached, some species can regrow a complete new disc from a single arm.

Oceana came across some of these sea stars during our 2012 Baltic expedition and we have proposed the creation of several MPAs that include its habitat, such as Marstrandsskärgården and the Kattegat Trench.