Cryptic Species of Sea Potato

The Sea Potato, Echinocardium cordatum

A member of the Heart Urchin family (Loveniidae), the Sea Potato (Echinocardium cordatum) is probably most familiar to most people from the testsof the dead animal washed up on seashores. Live specimens can be quite elusive as the animal burrows into fine sand using the dense mat of spines that cover its body (1). It burrows to between 10 and 20 cm from the intertidal to the subtidal and the offshore (2), where it acts as a deposit feeder, using its tube feet to collect particles (3).

Empty Test of Echinocardium cordatum

E. cordatum is found in temperate oceans all over the world, and was considered a cosmopolitian species (2). However sequencing of ribosomal DNA from individuals from Atlantic and Mediterranean populations showed that two distinct monophyletic groups exist, and suggests that the species may be actually represent several taxa, a complex of cryptic species (4). Using fossil data, it was estimated that divergence between the two groups occurred c. 6 million years ago.

Echinocardium cordatum Burrowing into Sandy Substrate

References:

1. Sterry, 2004 Collins Complete Guide to Irish Wildilfe p. 176
2. Egea et al., 2011 Comptes Rendus Biologies (In Press, Uncorrected Proof)
3. Challinor et al., 1999 A Beginner's Guide to Ireland's Seashore p. 167
4. Chenuil and Feral, 2003 Echinoderm Research 2001 pp. 1-7