The black-lip pearl oyster, Pinctada margaritifera, has a wide geographic range extending from Baja California across the Indo-Pacific basin to the Red Sea, and northwards into the Eastern Mediterranean Sea. These regions enclose a number of suitable habitats for the oyster that feature coral reefs and lagoons. There are seven subspecies of Pinctada margaritifera; each has a particular local distribution within the range of the species.
typica: Ryukyus, Taiwan, Australia, Micronesia and Melanesia; cumingi: Cook Islands, French Polynesia; mazalanica: Panama Bay, Baja California; erythraensis: Red Sea; persica: Persian Gulf; zanzibarensis: East Africa, Madagascar, and the Seychelle Islands; galtsoffi: Hawaiian Archipelago. (Sims, 1993; Yukihira, et al., 1999)
Common habitats of Pinctada margaritifera include lagoons, bays, and sheltered reef areas to about 40 m depth. The oyster prefers oligotrophic coral reef waters with low turbidity. The oyster is epifaunal, using byssal threads to attach to hard surfaces such as rocks and the shells of conspecifics. The greatest density of P. margaritifera is in the atoll lagoons of eastern Polynesia, harboring some 7 million oysters with 5 million living in the Penrhyn lagoon and 2 million in Manihiki Lagoon. (Sims, 1993; Yukihira, et al., 1998)
Pinctada margaritifera features a black shell with a black, non-nacreous border, and is one of the largest species in its genus. In the Cook Islands and throughout most of French Polynesia, this species can grow to an average of 130 mm. From samples collected at Orpheus Island, Australia, individuals reached 146 mm in shell width, and had tissue mass ranging from 5.5 to 8.8 g. The oyster is known for producing black pearls cultured throughout a number of regions, including French Polynesia and the Cook Islands. (Sims, 1993; Yukihira, et al., 1999)
The larval stage of Pinctada margaritifera can last for 16 to 30 days with an average daily growth rate of 3.7 to 5μm; development time is largely dependent on factors such as temperature and nutrition. The planktonic larva is known as a veliger, which develops a type of swimming mechanism called a ciliated velum also used for food transfer. At some point, the veliger will grow an appendage used to move across hard surfaces. Within the first 2 years of life, the shell may grow between 100 to 120 mm. At two years of age, the oyster has matured into an adult capable of reproducing. (Sims, 1993; Van Dyke, 2011)
All bivalves are broadcast spawners; gametes released by an individual may combine with those of multiple conspecifics. (Sims, 1993; Van Dyke, 2011)
Pinctada margaritifera is a protandrous hermaphrodite. It begins life as a male and later changes into a female. Pinctada margaritifera reaches sexual maturity around 2 years of age which is also around the same time the animal changes its sex. Pearl oysters reproduce by spawning, releasing their gametes into the open water for fertilization. Spawning is dependent on a number of factors which include salinity, currents, air exposure, and temperature. Oysters in temperate regions show more distinct seasonality in spawning, while tropical oysters have more of a year-round, intermittent schedule. Timing of spawning varies greatly from region to region. In the Red Sea, spawning occurs from March through September. However, there are two spawning seasons in Australia, one between July to August, and one in November. (Sims, 1993; Thielley, et al., 1993; Van Dyke, 2011)
As broadcast spawners, there is no parental investment. Young develop independently in the water column, drifting as plankton. (Sims, 1993)
During the larval phase, Pinctada margaritifera is most vulnerable to predators and changing currents. After settlement, the rapid growth rate of the oyster significantly decreases its vulnerability to predators. On average, P. margaritifera has a lifespan of 15 years. (Sims, 1993; Van Dyke, 2011)
After settlement as a postlarva, P. margaritifera spends a large amount of time seeking a compatible substrate (usually in a dark area) to bind to with its byssal threads. If such a substrate cannot be found, the oyster will migrate to a different location using its foot. (Sims, 1993)
Black pearl oysters are sessile, and do not have a home range or territory.
Little is known about communication in Pinctada margaritifera. Marine invertebrates in general are known to detect the presence and spawning activity of conspecifics by sensing dissolved chemicals.
Pinctada margaritifera is a nonselective filter feeder that feeds mainly on plankton. It is found in oligotrophic coral reef atolls, where there is a low amount of productivity. Studies have found mud, inorganic materials, and other less than ideal items within its digestive tract. (Sims, 1993)
Despite the protection of their calcareous valves, P. margaritifera is especially vulnerable to predation by sharks and rays. Other predators include octopus, starfish and predatory gastropods. In particular, the gastropod Chicoreus virgineus is described as the most dangerous predator for unprotected P. margaritifera within the Red Sea. Mud worms were responsible for the majority of P. margaritifera deaths in Palau. Pearl oysters are most vulnerable as larvae, because they are eaten by planktivores and are easily swept away from desirable benthic areas by ocean currents. (Loret, et al., 2000; Sims, 1993)
Bivalves are important in influencing phytoplankton concentrations through “top-down” grazer control. This action reduces particle density within the water and increases the amount of light which can reach benthic organisms. Bivalve waste can be assimilated as food for phytoplankton growth. Furthermore, the oyster beds form a sheltering hard-substrate habitat, housing numerous epifaunal and infaunal invertebrate species, and the oysters themselves are food for higher-order carnivores. Several types of Sporozoa are common parasites associated with Pinctada margaritifera and responsible for a large number of mollusk deaths. A number of parasitic annelid worms of the genus Polydora have had a similar effect on oyster mortality in the Persian Gulf. (Chagot, et al., 1993; Mohammad, 1972; Newell, 2004)
Pinctada margaritifera has been cultivated into a major commercial species for the pearl industry. Tahitian black pearls, derived from P. margaritifera and from Pinctada maxima account for about half of the world market. The pearl industry earned $18 million in exports for the Cook Islands in 2000. However, these numbers have substantially decreased due to a decrease in international pearl prices and problem with disease in Manihiki. In 2002, revenue fell to less than $11 million which includes profit from other forms of jewelry. Oysters of the genus Pinctada are not typically harvested for food, as other oyster species are. (McKenzie, 2004; Van Dyke, 2011)
There are no known adverse effects of P. margaritifera on humans.
Pearls produced by P. margaritifera are valuable export items in the economies of Indo-pacific island nations. Because it is an important mariculture species, its farming locations are subject to environmental management to prevent negative human impacts on the oyster’s growth and health. Pinctada margaritifera has no special conservation status. (McKenzie, 2004; Van Dyke, 2011)
Albert Gamez (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Angela Miner (editor), Animal Diversity Web Staff.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
an animal that mainly eats plankton
condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products
structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
remains in the same area
non-motile; permanently attached at the base.
Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa
reproduction that includes combining the genetic contribution of two individuals, a male and a female
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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