Surely a very rare glimpse of the secret life of a Heart Urchin or Sea Potato. These photographs show a specimen of Echinocardium cordatum (Pennant) emerging from its burrow in the wet sand at low tide on the shore at Port Eynon, Gower.
Its movements, as it surfaces, describe a circular path because it can only travel forwards and not backwards or sideways. The spines are coated with a layer of wet sand but you can see a clear channel is maintained for the tube feet or podia to move in and to assist with the passage of water. The channel or tunnel is formed by the spines over-arching the central ambulacral groove.
For more information about Sea Potatoes or Heart Urchins, look at the earlier posts: Sea Potatoes from Gower and Living Sea Potato sea urchin at Port Eynon.
Revision of a post first published 21 October 2009
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Jessica,
How rare are these and are they only present in Europe? We found hundreds of the shells on a beach near our home in Ireland at the end of August and sent some shells to family in the US. They collect but have never seen these urchins on their Eastern coast.
Any thoughts?
John
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Hello, John
I don’t think the Sea Potato type of sea urchin is particularly rare and its distribution is not confined to Europe. Echinocardium cordatum (Pennant) – as is illustrated in my blog – is said to be common to abundant on all British coasts and is almost cosmopolitan from Norway to South Africa, the Mediterranean, Australia, and Japan – being absent from North America. Although this particular species of burrowing sea urchin is not mentioned as occurring on the coasts of North America, a related species called Brissopsis lyrifera (Forbes) commonly lives, sometimes in abundance, on the east coast of North America as well as on all British coasts except in the south, from Norway and Iceland (but not Greenland) to South Africa and the Mediterranean. Brissopsis lives buried in mud, sublittorally (off-shore) in depths of water from 5-500m. Echinocardium lives in sand, mainly intertidal on shores but also sublittoral to depths of 230m.
[This information was found in Handbook of the marine fauna of north-west Europe Edited by P.J.Hayward & J.S.Ryland, Oxford University Press, 1998, ISBN 0 19 854055 8]
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The foot-wounds from the spikes take about three weeks to heal.
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OUCH!! Sounds like you’re speaking from experience.
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