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

Go East - Where the fossils lie!

Happy as a piddock in a rock

A huge fossil

A sea potato (Echinocardium cordatum)

Another crinoid (from Garryvoe)

Covered in fossils

Rugosa coral

and another

Rock from Ballybrannigan

Bryzoan fossil

Brachiopod fossil

Gastropod fossil

Showing to 2 parts of the rock found in Ballybrannigan....

....reavealing a crinoid fossil

A guest post by Ken.

Date 190210

Today we decided to go East. Two beaches we visited there, one in Ballybrannigan and the other in Garryvoe.

Ballybrannigan is near Cloyne, Co. Cork and is a really beautiful strand. We found brilliant specimens of crinoids and one particular coral species. We can see the segmented strands so maybe it could be a graptolite. In one rock I found the bryzoan, a little brachiopod and possilby a gastropod.

In Garyvoe, Ballycotton Bay we found another great crinoid specimen. Also we discovered a huge boulder covered in brachiopod fossils aswell as a few horn-coral fossils (Order Rugosa). Overall the day was a boon for fossils.

In Garryvoe we noticed that a lot of the limestone rocks were riddled with holes. These were caused by piddocks (Pholas dactylus). Pinn et al. 2005 note that these bivalves bore into the substratum and suggest that, because of this cryptic lifestyle, we know very little about their biology or ecology. However we do know that early naturalists were fascinated by their luminescence and boring ability. The luminescent properties even while being eaten was noted as early as AD77 by Pliny the Elder. And the Romans were reported to have eaten them. [Pinn et al. 2005 Burrow morphology, biometry, age and growth of piddocks (Mollusca: Bivalvia: Pholadidae) on the South coast of England Marine Biology 147 pp. 943-953].

See picture above of the piddock happily nestled in the rock (he's dead btw!).

We found a lovely specimen also of a sea potato (Echinocardium cordatum), a heart-shaped sea urchin adapted for burrowing.

Anyway, another great day for the 21st Century Naturalists.

Goodnight.