ShanaRae Lim Oysters are classified as shellfish, covered with a shell, or invertebrates, having no backbone. They are further classified as mollusks, mollusks are of soft structure and are either partially or wholly enclosed in a hard shell that is largely of mineral composition.
All shellfish have some carbohydrate in the form of glycogen.
Oysters have from 3 to 5 percent. Oysters also contain a somewhat higher percentage of calcium than other fish and meats, which are notably low in calcium. Marine fish are a dependable source of iodine. Oysters, clams, and lobster are the highest in iodine of all seafood. When alive, they have a tightly closed shell.