Oysters encompass a number of bivalve mollusk species which live in the ocean and around reefs. They are identified by their mottled rock-hard shells, which may be shaped like teardrops or ovals. They're are also known to change genders during the course of their lives. Oysters have great value both as a food and as part of a healthy ecosystem.
Oysters are a good choice of food for health conscious diners. You can eat them raw under certain conditions, as well as cooked. They are loaded with omega-3 fatty acids which fight bad cholesterol. In addition, oysters contain zinc, a vitamin that reduces the risk of certain vision disorders and is also necessary to the immune system. They also contain tyrosine, an amino acid that is useful to the brain and for improved mental performance. Oysters are high in vitamin D, calcium, vitamin B, protein, healthy cholesterol and iron, while also being low in saturated fat.
Since the time of Cleopatra, people have used oysters as an aphrodisiac. According to legend, eating raw oysters boosts your sex life. While there is still a raging scientific debate over whether this is true, recent studies do suggest that unique types of amino acids found in these shellfish--D-aspartic acid (D-Asp) and N-methyl-D-aspartate (NMDA)--may boost sexual performance. The high zinc content in oysters may also be helpful in raising the libido of men who eat them. Therapists recommend eating oysters to help with sexual disorders because of their high iron content.
Oysters filter water through their vents, consuming algae in the process. Given large enough numbers of oysters, they can clear up the water and allow underwater plants to receive sunlight, which results in the plants creating more underwater oxygen that fish need to live. Oysters create spawning grounds as well as habitats for other animals like fish and blue crabs, which come there to hide from predators.
Certain oysters are farmed and valued for their ability to make pearls. Known as "pearl oysters," they are not the same oysters as the ones that people eat. While edible oysters can produce pearls along with most other mollusks, the ones used to produce gemstones of commercial value are more closely related to clams than oysters. Pearls form when the mollusk reacts to an intruder or other irritant by coating it in layers of calcium carbonate, which typically forms into a smooth and round enclosure.