Our favorite restaurant, although Pieter can't remember its name - Mr Wooby's. It was on Salamanca square. Great oysters!
From "Little Known Facts About Oysters" by Ilene Polansky
How Oysters Breathe
Oysters breathe much like fish, using both gills and mantle. The mantle is lined with many small, thin-walled blood vessels which extract oxygen from the water and expel carbon dioxide. A small, three-chambered heart, lying under the abductor muscle, pumps colorless blood, with its supply of oxygen, to all parts of the body. At the same time a pair of kidneys located on the underside of the muscle purify the blood of any waste products it has collected.