Oysters are loved by millions of people but most people know them only by their appearance and taste, at the dinner table. Or, they know that oysters produce the beautiful pearls that many women long to wear. Not many people know that oysters really breathe like a fish, using gills and mantle. The oyster also has a heart with three chambers and colorless blood.
There are over 400 species of oysters known to man. Only one oyster in over a million will live to see adulthood. There are records dating back to ancient Roman times proving that they also ate oysters, often smoking them over fires. There’s actually proof that oysters have been around for about 15 million years. Fossils of oysters have been found in certain places that are 50 feet thick, showing that the mollusk was plentiful then as now.
There is no known way of telling a female oyster from a male oyster, at least not by looking at their shells. And if you could tell the difference it wouldn’t really matter since, in fact, oysters can change between the two sexes at will. Although usually born male an oyster will likely change its sex a few times during its life.
A small species of crab, called the Pinnotheres ostreum, often lives in the shell with an oyster. Although the crabs don’t live in every oyster, it’s not unusual to find one, on occasion, living harmoniously inside the oyster’s shell. No one knows exactly why the crab is permitted to move in but the oysters seem okay with the arrangement.
When a minuscule piece of foreign material enters the oyster’s shell, and the oyster can’t seem to repel it, the oyster begins coating the object with calcium and protein, called nacre. After awhile the layers of nacre become what is known as a pearl. Although the white pearl is the most common, pearls have also been found in colors from yellow to pink to black.
Oysters filter water by sucking it in and spitting it back out again. By doing this they can gather food particles from the water. An average oyster can actually filter over 50 gallons of water per day! While filtering the water they remove such things as gold, mercury, arsenic and lead.
One myth about oysters is that you should never eat them in months that do not have an “r” in the name of the month. So, September through April would be safe months to eat them, but eating them in other months would make you sick. This is simply not true. Oysters can be eaten any time but the myth began many years ago. Before refrigeration, summer months (month without “r’s”) would be a risky time to eat oysters that hadn’t been kept chilled.
Oysters are healthy foods, too. They contain protein, carbohydrates and lipids and are ideal for low-cholesterol diets. They also contain vitamins A, B1, B2, B3, C, and D. In addition, eating five average-size oysters provide the daily allowance of magnesium, calcium, iron, copper, zinc, iodine, manganese and phosphorus.