The Genus Pinctada

Pinctada History and Discovery

Historically there is a large amount of duplication among the names of pearl producing mollusks. This is partly due to independent geographical discoveries that were later found to be the same oyster. Furthermore the crossover between a subspecies and a unique species is vaguely defined. Discoveries may originally be noted as a subspecies and then later revised to belong to a unique species and vice versa. Due to these reasons, there are numerous synonyms for most of the pearl producing mollusks. Other names for Pinctada are Avicula (aviculides), Meleagrina and Margaritifera . Although the name Pinctada first appeared in 1798 as part of J.F. Bolten's classification, it did not resurface until 1915, and was not widely accepted until the 1970's.

Pinctada shells serve as the main identifier of the Pteriidae family. Though it is their thick, nacreous lining that distinguishes the pearls of a particular species, the shells serve as a main tool for identification. The hinge that connects the two halves of a Pinctada shell can either have small ridges (“teeth”) or a smooth lip. In 1901, English zoologist Jameson classified 34 species of Pinctada and divided them into two groups: those with teeth (such as those producing Akoya and Mabe pearls) and those without (such as those producing Tahitian and White South Sea pearls). Jameson's method was revised and clarified by G. Ranson in 1961. Ranson provided detailed descriptions and measurements of the shells that clarified what constituted “teeth” in a shell. He also included information on habitat, geographical distribution and synonyms. Though there has been considerable disagreement on his nomenclature and classification, Ranson's work is the most comprehensive classification to date.

Pinctada Habitat & Ecology

Most Pinctada shells are found in the Carob-Pacific and Indo-Pacific. They have never been reported on the west coast of Africa or around the islands of the eastern Atlantic. The two major pearl-mollusk regions are known as the Western (Carib-Pacific) and Eastern (Indo-Pacific). In both regions, all precise locations for Pinctada have water temperatures that rarely fall below 20 degrees C (68 degrees F) and are usually higher. The size and growth rate of Pinctada corresponds directly to water temperature. In warmer waters, shells are generally larger and grow faster. The size of a pearl is often an indication as to what region the pearl originated (larger pearls generally come from larger shells). Though there may be regional differences in a species' shell size and shape, the inner soft body that produces the pearl of a particular species is the same throughout. For this reason, a geographical discovery of a different looking shell sometimes leads to falsely creating a new subspecies when the inner soft body, and thereby the pearls, had previously been recorded.

Pinctada generally cluster in large, dense colonies. Sometimes they are found in shallow water but generally thrive in 30-120 feet water. Although water temperature and food supply contribute to the ultimate depth, seabed conditions is the primary factor. Pinctada require a firm foundation for the mollusk to adhere to through a web of organic threads called byssus. Main hazards for Pinctada farming include pollution, natural predators, overcrowding and shifting currents/weather.

The Pearls of Pinctada

The genus includes most of the pearls that are found in fashion. From the exotic South Sea pearls (Pinctada maxima) to the classic Akoya pearls (Pinctada fucata), shells from the genus Pinctada inspire the majority of pearls' fashion portfolio. Some shells of Pinctada maxima are so large that they are of “dinner plate” diameters and were historically critical to the Mother of Pearl industry. Also included within Pinctada are Tahitian pearls (Pinctada margaritifera) and tiny natural Pipi pearls found from the Indian Ocean to the Central Pacific (Pinctada maculata).