(Health Secrets Newsletter) Bivalves are a type of Mollusk. There are four main types of bivalves including clams, oysters, mussels and scallops, under which there are many families and species. This article will briefly summarize the health benefits of bivalves and will provide an overview that covers nearly 40 of the most common species. Each is organized according to their type and family. Note that there are many ways to group bivalves and this is simply one attempt. Future articles will explore each of the four types of bivalves in detail.
June 14, 2012
Nutritional Content of Bivalves
Bivalves are an excellent source of protein and contain a number of vitamins and minerals including vitamin C, iron, manganese, phosphorous, selenium, and zinc. Bivalves are the #1 source of vitamin B12 (known as Cobalamin). Foods high in vitamin B12 help prevent anemia, fatigue, mania and depression. Bivalves are easily digested and commonly served raw. Bivalves should always be purchased and cooked (or consumed) when live. They should not be consumed when both frozen and raw. If steamed, they are cooked once they open. Never force open a cooked bivalve that remains closed as they are likely to contain rotten meat.
Outline of Bivalves
Clams – There are about 2000 types of clams, all of which are filter feeders. They are organized in many ways, but there are three main categories. Hard shell clams have a thicker shell that can withstand higher salinity. They are found on both coasts of north America which is how the two main types are organized.
East Coast Hard clam – These are the Northern Quahog clams that consist of Littleneck (small), Cherrystone (medium), Chowder (large), and the Southern Quahog clam.
West Coast Hard clam – These consist of Pacific Littleneck, Pismo, Butter, and Manila varieties.
Soft shell clams are not actually pliable but rather have a thinner shell that is more easily broken. They are best steamed open or fried, and are called Steamers. Varieties are Essex, Ipswich and Longneck.
The third category of clams is the non-native. These are the Pacific Razor that has an elongated oval-shaped shell, and the Geoduck which is a giant clam from the Pacific Northwest that is among the world’s largest.
Oysters – This is a common name for a number of distinct groups within the bivalve mollusks that have highly calcified valves. Oysters are filter feeders and play a critical role in water purification as they absorb and process toxins into their shells. Types include:
True oyster – This is the type most commonly eaten by humans and considered an aphrodisiac. There are many varieties including Belon, Eastern, Olympia, Pacific, and Sydney rock.
Pearl oyster – These are not related to either edible oysters or mussels. They have a strong inner layer composed of nacre or “mother of pearl”. Though edible, they are not often eaten by humans. There are many types of pearl oysters.
Thorny oyster – This type of oyster has many species and is known for sharp prongs along with a more advanced nervous system including optic lobes. Types include: Atlantic, European, Japanese, Nude, Pacific, Regal and Wright’s.
Saddle oyster – These have very thin, translucent, paper-like shells that often have holes from where the bivalve perched. The flesh is bitter and not palatable, but there are industrial uses such as making paint and shellac.
Mussels – Mussels is the common name that includes several families of the bivalve mollusks that are found in both fresh and salt water habitats. The word mussel normally means bivalves from the family Mytilidae, though other types such as Zebra mussels exist. Mussels are filter feeders that feed on plankton. Varieties are Mediterranean mussel, Blue mussel, and New Zealand Green-lip mussel.
Scallops – Scallops are cosmopolitan and found in all the world’s oceans. They are prized by shell collectors. The word scallop derives from the old French escalope which means shell. Scallops have up to 100 simple eyes around the perimeter of their ruffled shell. Most scallops are filter feeders. There are many types including Sea scallop, Atlantic Bay scallop, and Atlantic Calico scallop.
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