On the reverse side of the one thousand-peso bill, one finds the Pinctada maxima, the world’s largest pearl oyster and producer of the coveted South Sea pearl, superimposed against the Tubbataha Reefs Natural Park, which was declared a UNESCO World Heritage Site in 1993 for its pristine coral reef and high density of marine species.

By Patricia Calzo Vega

When the Bangko Sentral ng Pilipinas launched its New Generation Currency notes in 2010, it took the opportunity to feature some of the country’s most prominent indigenous species in their local environments. On the reverse side of the one thousand-peso bill, one finds the Pinctada maxima, the world’s largest pearl oyster and producer of the coveted South Sea pearl, superimposed against the Tubbataha Reefs Natural Park, which was declared a UNESCO World Heritage Site in 1993 for its pristine coral reef and high density of marine species. The park is located at the center of the Sulu Sea, within the Coral Triangle.

Region and habitat The species is present in twenty-two countries across Asia and Oceania; SeaLifeBase.org lists P. maxima as native to five tropical marine ecosystems: the Indian Ocean, Indonesia Sea, Pacific Ocean, West Philippine Sea (South China Sea), and the Sulu-Celebes Sea. P. maxima oysters grow in dense colonies and can inhabit a variety of habitats, ranging from sand and mud to seagrass beds, deep water reefs, or soft corals, for as long as these are within littoral (close to shore) and sublittoral (between low tide line and edge of continental shelf) zones. The species is known to thrive in clear water, under influence of currents, most commonly at depths of 5 to 30 meters, though there have been sightings at 60 meters.

Characteristics and behavior As can be inferred from the ‘maxima’ in its scientific name, this particular species of pearl is outsized, with a thick and large subcircular shell that reaches up to 30 cm in length; its posterior ear is short and ill-defined, while an anterior margin protrudes beyond the tip of its anterior ear. The outer surface of its shell is covered in overlapping, concentric scales with large, irregular blunt-tipped spines; these are arranged in radial rows along the shell margin.It bears a uniformly brownish color streaked with radial stripes in green, dark brown, or purple. Unlike other bivalves, the pearl oyster has a hinge devoid of teeth.

The P. maxima oyster comes in two varieties: silver-lipped and gold-lipped. These can be distinguished by the color proportions of its internal nacreous (mother of pearl) area, which is described as highly lustrous and silver in color, but with a variably extended golden border. Oysters are filter feeders, straining plankton, bacteria, and other nutrients from the water passing through their gills.

Like most bivalves, the pearl oyster functions as a protandous hermaphrodite; it first takes on male sexual characteristics in the first three to four years of its life (at 110-120 millimeters or mm in size), then transforms into a female. At 170 mm, half the population is male and female, but by the time the oysters reach 190 mm, all individuals of the population are female. Spawning primarily occurs between mid-October to December, with a secondary spawning period from February to March. Sperm and egg are spawned directly into water; fertilized eggs turn into veliger larvae and settle into the seabed within 28 to 35 days. If an appropriately hard surface is found, the veliger settles into the juvenile “spat” (larvae attached to a hard substrate) stage, forms a shell, and becomes a sedentary bottom-dweller. P. maxima can live for up to 40 years.

Pearl farming The lucrative South Sea pearl trade has ensured the continued breeding of P. maxima oysters for commercial purposes; in fact, the vast majority of P. maxima colonies are found in pearl farms off the northern coast of Australia, some islands in Indonesia and Polynesia, the southern tip of Myanmar, and off the island of Palawan. The pearl farming cycle consists of four stages, beginning with spat collection.

Juvenile oysters, or spat, may be collected from the wild, or from hatchery breeding programs; in Australia, there are strict guidelines in place regarding the collection of adult pearl oysters in the wild. The next step is the grafting process, which takes place when the pearl oysters have reached maturation: oysters are temporarily removed from their ocean baskets for seeding. A nucleus and piece of donor mantle tissue is inserted into the pearl pocket. Once the grafting process is completed, oysters are returned to the ocean farms and cared for until the pearl is ready for harvest; the healthier an oyster, the greater chances of it producing a high quality pearl. Oysters are cleaned on a regular basis to prevent faunal and floral overgrowth on the oyster shell. It takes at least four years to harvest a South Sea pearl. Oysters that have produced high quality pearls will be grafted subsequent times.

Pearls of Trivia

• The Philippine pearl trade can be traced as far back as the Sung dynasty (960-1127 AD). The accounts of Chao Ju-Ku describe the barter trade between the Chinese and the natives of Ma-i (Mindoro). The list of goods exchanged include silk, porcelain, colored glass, beads, and ironware for the Chinese and hemp cloth, tortoise shells, pearls, and yellow wax for the Filipinos.

• The Philippines’ sobriquet “Pearl of the Orient” (Perla del Mar de Oriente) was first coined by the Jesuit missionary Fr. Juan J. Delgado in 1751.

• The largest pearl in the world, known as the “Pearl of Allah” or the “Pearl of Lao-Tzu” was found in Brooke’s Point, Palawan; an American, Wilburn Cobb, transported it from the Philippines to the United States. The pearl, with dimensions of 24 centimeters in diameter (9.45 inches) and 6.4 kilograms (14.1 lb), is a non-nacreous pearl, having been created by a giant clam instead of a nacre-bearing pearl oyster. The second largest pearl was also discovered in Palawan and is called the “Palawan Princess.”

• On October 15, 1996, President Fidel Ramos signed Proclamation No. 905, which declared the South Sea Pearl, also known as the Philippine Pearl, as the country’s national gem. This proclamation was made upon the suggestion of the Department of Tourism

• Jewelmer, a Filipino-French South Sea pearl company, was the first company to successfully produce a consistently golden South Sea pearl. The high quality of its trademark pearls, along with an effective marketing campaign, led to the acceptance of gold pearls as a luxury item, and paved the way for the entry of other colored pearls in the luxury jewelry market.

This appeared in Animal Scene’s August 2015 issue.