Perhaps more commonly known as a pumpkin pansy or the sea potato, the heart urchin Echinocardium cordatum is a beautiful irregularly oval urchin which is usually 4-5 cm in length, but can grow up to 9 cm. The body is covered in short spines, which are mostly directed backwards, unlike other sea urchins found in our waters. However, by the time they have washed up they have mostly lost their spines, and an interesting pattern of small holes on the rounded top, and a scoop-like lip on the flattened underside can be seen. Besides being found in South Africa, this species is found in temperate waters around Australia, New Zealand, the Gulf of California, and the British Isles. Heart urchins burrow beneath the sand to a depth between 8-15 cm, and can be found subtidally to a depth of 200 m. The burrow is made with a respiratory channel which leaves a funnel-like depression in the sand, showing the location of the individual. Living in the sand this species feeds on detritus within the sand, using its tube-feet to pick up particles, even extending tube-feet up the respiratory channel to pick up detritus which collected in the entrance to the respiratory channel.
Written by: Minke Witteveen
For further reading:
- Branch, G.M., Griffiths, C.L., Branch, M.L. and Beckley, L.E. 2010. Two Oceans: A guide to the marine life of southern Africa. Pp. 236. Random House Struik Publishers, Cape Town.
- Fish, J.D. and Fish, S. 1989. A Student’s Guide to the Seashore. Pp 384-385. Unwin Hyman Ltd, London.