Let it shine

During this past week while conducting surveys in Bodega Harbor, I heard Eric say quietly, "You're not going to believe what I found."  I turned to look and could see this animal attached to the rock (it's ~3 cm wide):

 

The shells of these animals look like those of clams or scallops at first, but they have a distinctive shape that provides a hint that you're looking at something different.

This is the first time we've seen a live brachiopod in the Bodega Bay area.  Meet the North Pacific Lamp Shell (Terebratalia transversa)!  They're more common in deeper water (e.g., we've seen then come in on nets removed from Cordell Bank), but we found this one in the low intertidal zone.

Outwardly they look like bivalves, but internally brachiopods are more similar to phoronids.  Just like phoronids, they have a lophophore — a ring of coiled tentacles for feeding (see photos of phoronid lophophores here).  In brachiopods, the lophophore is not extended into the water, but is nestled between the two valves.  This body plan is unique, so these animals belong to their own phylum (Brachiopoda).

Here's another view:

 

P.S.  Brachiopods are sometimes called lamp shells because they're thought to resemble ancient Roman oil lamps.  Although you can't see it in these photos, one of the valves has a hole in it through which a stalk extends to attach to the rock.  The shape of the valve along with the hole look similar to a discus lamp with a hole for the wick (see examples here).