by Ilene Polansky
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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.
Oysters Male or Female
There is no way of telling male oysters from females by examining their shells. While oysters have separate sexes, they may change sex one or more times during their life span. The gonads, organs responsible for producing both eggs and sperm, surround the digestive organs and are made up of sex cells, branching tubules and connective tissue.
What is that tiny crab we see in an oyster?
It is a species of crab (Pinnotheres ostreum) that has evolved to live harmoniously inside an oyster's shell. These dime-sized crabs, much sought after by gourmands, are not abundant.
How do pearls end up inside of oysters?
An oyster produces a pearl when foreign material becomes trapped inside the shell. The oyster responds to the irritation by producing nacre, a combination of calcium and protein. The nacre coats the foreign material and over time produces a pearl.
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The "R" Myth
Folklore says that oysters should be eaten only in months with "r's" in them—September, October, etc. Maestro S.V.P. educates people that oysters can be eaten 12 months a year. The notion that oysters should not be eaten in "r"-less months—that is, months that occur during warm weather—may have started in the days when oysters where shipped without adequate refrigeration and could spoil. But today all that has changed and we can enjoy oysters twelve months a year.
Oysters and Their Nutritional Value
Oysters are not only delicious, but they're also one of the most nutritionally well balanced of foods, containing protein, carbohydrates and lipids. The National Heart and Lung Institute suggest oysters as an ideal food for inclusion in low-cholesterol diets. Oysters are an excellent source of vitamins A, B1(thiamin), B2 (riboflavin), B3 (niacin), C (ascorbic acid) and D (calciferol). Four or five medium size oysters supply the recommended daily allowance of iron, copper, iodine, magnesium, calcium, zinc, manganese and phosphorus.
Because raw foods including oysters may carry bacteria, persons with chronic liver disease, impaired immune systems or cancer should avoid eating raw oysters.