Oyster is a name common to several families of fresh-water bivalve mollusks that dwell in brackish or marine habitats.
A good number of oysters are in the Ostreoidea superfamily, though not all.
Oysters generally have health benefits as they are rich in zinc, which is crucial for producing testosterone and maintaining healthy sperm.
Even though men have more testosterone than women, oysters also help in maintaining and increasing the level of libido in women.
They are great dopamine (the hormone responsible for increasing the libido level in men and women) boosters.
Various oysters are either eaten raw or cooked. In some instances, they are used as ornaments or pearls for decoration.
Scientific Classification
- Scientific Name: Ostreidae
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Bivalvia
- Subclass: Pteriomorphia
Types
There are different types of oysters, but we will consider only two major types: Pearl and True.
Pearl Oysters
Pearl oysters are those types that secrete pearls, though some are sometimes not valuable.
Two types of pearls, natural and cultured pearls, can be obtained from pearl oysters, although freshwater mussels, which are also mollusks, also produce pearls that are valuable commercially.
Notably, marine Pinctada maxima is the largest pearl-yielding Oyster, about the size of a dinner plate. Naturally, pearl oysters usually produce pearls by covering small incursive objects with nacre. The pesky object has covered nacre layers for years to become a pearl.
Different colors, types, and shapes of pearls are contingent on the original irritant’s shape and the nacre’s natural pigment.
A pearl can be cultured by pearl farmers simply by placing the nucleus inside the Oyster, usually of polished mussel shell. Oysters can produce a perfect pearl within 3 to 7 years.
True Oysters
True oysters belong to the Ostreidae family, consisting of edible oysters, primarily Crassostrea, Magallana, Ostrea, Ostreola, and Saccostrea.
Eastern oysters, Pacific oysters, Sydney rock oysters, etc, are good examples.
Anatomy
Oysters are regarded as filter feeders; by beating their cilia, oysters can draw water in over their gills.
Trapped particles in the mucus of a gill, as well as plankton that are suspended, are transported to the mouth, where these particles are eaten, digested, and excreted as waste products (pseudo feces).
They mostly feed at a temperature of 10°C and above. They can filter water up to 5 liters per hour. Surplus nutrients, algae, and deposits can cause a body of water to become eutrophic and become subject to eutrophication.
There also exists an interchange of gases across the mantles of oysters, in addition to their gills, lined with thin-walled, small blood vessels.
A minute heart with three chambers beneath the adductor muscle pumps colorless blood to all body parts.
Also, two kidneys, located directly beneath the muscle, expel waste products from the blood. Oysters also have a nervous system that comprises two pairs of nerve cords and three pairs of ganglia.
Some oysters have two reproductive systems (both sperm and eggs), which makes it technically possible for them to fertilize their eggs; an example of these is the European and Olympian oysters.
The digestive organs are surrounded by gonads, which are made up of branching tubules, sex cells, and connective tissue. When the female oyster fertilizes, she dispatches millions of eggs into the water.
The larvae of the Oyster then become suspended in the water column as veliger larvae for about three weeks, after six hours of developing into the larvae, before settling on a bed and then maturing into sexual adulthood within a year.
Habitat and Behavior
Oysters, being a linchpin species, provide habitat for several marine species. Species of oysters like Saccostrea and Crassostrea mainly dwell in the intertidal zone.
The corners between the hard surfaces of oyster shells provide shelter and a habitat for other small animals. The Oyster reefs are inhabited by barnacles, sea anemones, etc.
The reef of an oyster can increase the surface area of a flat bottom by 50-fold. The mature shape of an oyster is contingent on the type of bottom to which it is attached originally, though it usually aligns itself with its flared outer shell tipped upward. Usually, oysters attend a state of maturity within a year.
They breed as males by releasing sperm into the water during the first year. Next, they breed as females by discharging eggs. This occurs as they grow over two or three years and develop greater energy reserves.
Another type of oyster, known as bay oysters, mostly breeds from the end of June until mid-August.
An increase in the temperature of water causes some oysters to breed. As a result, a female oyster can discharge 100 million eggs and above yearly.
Spats are attached oyster larvae fertilized and settle in another oyster’s shell. These spats are 1 inch long.
Oysters are believed to filter large amounts of water to feed and breathe (exchange O2 and CO2 with water) but are not open permanently. They constantly close their valves to enter a dormant state, even permanently immersed.
Their behavior follows strict circulated and circadian rhythms according to the relative sun and moon positions. They have much longer closing periods during low tide than during spring tide.
Mangrove oysters, which dwell in the tropics and are part of the family Ostreidae, grow best on mangrove roots.
As Food
Oysters can be eaten steamed, stewed, fried, broiled, baked, or roasted with various drinks. In countries like Malaysia, fried oysters with egg and flour are a common delicacy.
Poached oysters can be served with cream roux on toast.
