Pearl oysters are members of the phylum Mollusca and belong to the class Bivalvia. Bivalve mollusks are distinguished by having two shells (two valves), a soft body with a small foot, a byssal gland and paired gills. Pearl oysters are protandric hemaphrodites, which means that most are first male, then female. The male phase usually occurs during the first 2-3 years of life, with the change to the female phase in later years. Pearl oysters have been reported to live as long as 25 years.
Fig. Anatomy and life cycle of Pearl oysters.
Pearl oysters reproduce by releasing millions of eggs or sperm into the water column, where fertilization occurs randomly. In less than 24 hours, the fertilized egg develops into a trocophore larva, a free-swimming organism (Figure). The larvae remain suspended in the water column for 2-3 weeks before undergoing metamorphosis, changing into an attached juvenile “spat.” Shortly before metamorphosis, the larva develops an enlarged foot and an eye-spot. The foot remains after metamorphosis, and the young spat retains the ability to move about for several months even after it attaches itself to a hard substrate. Pearl oysters can attach and reattach themselves using the byssus. Pearl oysters feed on small algae found in the water column. The gills in bivalves are large, and tiny hair-like cilia on the gills are used to remove small particles from the water. Both adults and larvae feed on algae and other small organisms. Clear tropical waters contain limited amounts of algae. Therefore, a large amount of water must be filtered daily in order for the pearl oyster to obtain sufficient food. This is the reason that importance is placed on not crowding pearl oysters on the farm and for keeping the shells clean of organisms that compete for food.
Fig. Anatomy and life cycle of Pearl oysters.
Pearl oysters reproduce by releasing millions of eggs or sperm into the water column, where fertilization occurs randomly. In less than 24 hours, the fertilized egg develops into a trocophore larva, a free-swimming organism (Figure). The larvae remain suspended in the water column for 2-3 weeks before undergoing metamorphosis, changing into an attached juvenile “spat.” Shortly before metamorphosis, the larva develops an enlarged foot and an eye-spot. The foot remains after metamorphosis, and the young spat retains the ability to move about for several months even after it attaches itself to a hard substrate. Pearl oysters can attach and reattach themselves using the byssus. Pearl oysters feed on small algae found in the water column. The gills in bivalves are large, and tiny hair-like cilia on the gills are used to remove small particles from the water. Both adults and larvae feed on algae and other small organisms. Clear tropical waters contain limited amounts of algae. Therefore, a large amount of water must be filtered daily in order for the pearl oyster to obtain sufficient food. This is the reason that importance is placed on not crowding pearl oysters on the farm and for keeping the shells clean of organisms that compete for food.
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