169
virginica are typically broadly oval and thick and grow to about 10–15 cm in length.
The lower valve is convex and upper valve flat, usually with concentric ridges and
lines. Exterior colour is dirty white to grey. The interior is bright white with a deep
purple or red-brown muscle scar (Eldredge and Smith 2001).
C. virginica are abundant in shallow saltwater bays, lagoons, and estuaries.
Oysters favour estuaries and embayments with low salinities and are intolerant of
prolonged exposure to fresh water or marine conditions. They are found in shallow
water of tidal to subtidal depth of constant turbidity and salinity but can withstand a
wide range of temperatures (Cabi 2019d).
The cupped Eastern oyster occurs in estuaries and marine coastal environments,
and is cultured in the United States, Canada, and Mexico. This species is marketed
fresh on the half shell and frozen, or incorporated into value added products, such
as soups and chowders (Heinonen 2014).
Saccostrea commercialis (Iredale and Roughley, 1933)
The Sydney rock oyster occurs in intertidal estuarine habitats, as well as on natural
subtidal dredge beds. The main producer country of this species is Australia. Sydney
rock oysters are cultured for the half shell market and are sold in supermarkets and
restaurants. The composition of oyster meat varies, depending on oyster type, breeding area, harvest season, feeding conditions at farms, spawning season, and oyster
size (Heinonen 2014).
Nutritive Composition of Oysters
The oyster contains vitamins A, B 1 , B 2 , C, D and E and a serving of 15 g of its meat
has the same amount of vitamin C as 3 g of lemon juice. Some important essential
amino acids (lysine, histidine, tyrosine) are also found in oyster meat. It is abundant
in minerals (Hasanspahić 2011).
It is reported that the main component of oyster meat is water, which is tightly
bound to proteins in the structure and is not easily released, even under high pressure, and is an index of freshness. The composition of oysters with high protein
content and low-fat levels is similar to the nutritional composition of other molluscs
(Table 3.3).
Carbohydrates that can be ignored in fish are found in significant amounts in
oysters (Asha et al. 2014). Energy stored in the form of glycogen prior to gametogensis is utilized during periods of high metabolic demand during the production of
gametes in oysters. Oysters begin to form and store glycogen after spawning and
glycogen content reaches a maximum a few months before the next spawning. It is
used as an energy source during the rapid proliferation of sex cells and by the end
of the reproductive cycle it is at a minimum (Linehan et al. 1999). It has been
reported that the glycogen content of the oyster changes seasonally (Berthelin et al.
2000). In a study, it was determined that the glycogen level of C. gigas was at the
maximum level in April before the gonad volume increased, and the lowest level in
August in relation to spawning (Perdue and Erickson 1984). Linehan et al. (1999)
3.1 Bivalves
virginica are typically broadly oval and thick and grow to about 10–15 cm in length.
The lower valve is convex and upper valve flat, usually with concentric ridges and
lines. Exterior colour is dirty white to grey. The interior is bright white with a deep
purple or red-brown muscle scar (Eldredge and Smith 2001).
C. virginica are abundant in shallow saltwater bays, lagoons, and estuaries.
Oysters favour estuaries and embayments with low salinities and are intolerant of
prolonged exposure to fresh water or marine conditions. They are found in shallow
water of tidal to subtidal depth of constant turbidity and salinity but can withstand a
wide range of temperatures (Cabi 2019d).
The cupped Eastern oyster occurs in estuaries and marine coastal environments,
and is cultured in the United States, Canada, and Mexico. This species is marketed
fresh on the half shell and frozen, or incorporated into value added products, such
as soups and chowders (Heinonen 2014).
Saccostrea commercialis (Iredale and Roughley, 1933)
The Sydney rock oyster occurs in intertidal estuarine habitats, as well as on natural
subtidal dredge beds. The main producer country of this species is Australia. Sydney
rock oysters are cultured for the half shell market and are sold in supermarkets and
restaurants. The composition of oyster meat varies, depending on oyster type, breeding area, harvest season, feeding conditions at farms, spawning season, and oyster
size (Heinonen 2014).
Nutritive Composition of Oysters
The oyster contains vitamins A, B 1 , B 2 , C, D and E and a serving of 15 g of its meat
has the same amount of vitamin C as 3 g of lemon juice. Some important essential
amino acids (lysine, histidine, tyrosine) are also found in oyster meat. It is abundant
in minerals (Hasanspahić 2011).
It is reported that the main component of oyster meat is water, which is tightly
bound to proteins in the structure and is not easily released, even under high pressure, and is an index of freshness. The composition of oysters with high protein
content and low-fat levels is similar to the nutritional composition of other molluscs
(Table 3.3).
Carbohydrates that can be ignored in fish are found in significant amounts in
oysters (Asha et al. 2014). Energy stored in the form of glycogen prior to gametogensis is utilized during periods of high metabolic demand during the production of
gametes in oysters. Oysters begin to form and store glycogen after spawning and
glycogen content reaches a maximum a few months before the next spawning. It is
used as an energy source during the rapid proliferation of sex cells and by the end
of the reproductive cycle it is at a minimum (Linehan et al. 1999). It has been
reported that the glycogen content of the oyster changes seasonally (Berthelin et al.
2000). In a study, it was determined that the glycogen level of C. gigas was at the
maximum level in April before the gonad volume increased, and the lowest level in
August in relation to spawning (Perdue and Erickson 1984). Linehan et al. (1999)
3.1 Bivalves