The Basic Methods of Pearl Farming: A Layman's Manual - CTSA

Basic biology and ecologyBasic biology and ecology of pearl oystersPearl oysters are members of the phylum Mollusca and belong to the class Bivalvia. Bivalve mollusksare distinguished by having two shells (two valves), a soft body with a small foot, a byssal gland andpaired gills. Although the common name of “pearl oyster” suggests a close relationship with othertypes of oysters, pearl oysters are actually a distinct genus from the edible oysters, Crassostrea andOstrea and have important anatomical and behavioral differences. The internal anatomy of a pearloyster is shown in Figure 3.Pearl oysters are mostcommonly found in tropicalareas. The Black-Lippearl oyster (Pinctadamargaritifera) is widelydistributed throughout thetropic Indo-Pacific area(Figure 4). There are severalsubspecies and strainsof P. margaritifera, includingthe Hawaiianstrain, P. margaritiferagalstofii, and the closelyrelated P. mazatlantica,which was considered astrain of the Black-Lip formany years.Figure 3. Internal anatomy of the pearl oyster (modified from George, 1978).Figure 4. Distribution of the major pearl producing species (adapted from Gervisand Sims, 1992)Black-Lip pearl oysters aregenerally found in areaswhere water temperaturesrange from 25 to 30°C. Below23°C, tropical speciesof pearl oysters stop breedingand may die. Whilepearl oysters can tolerate arange of salinities, they aremost common in water withhigh salinities (around 33ppt). They appear to growbest in clear waters that arefree of large amounts ofsediment since pearl oystersmay have difficulty feedingin turbid water.Page 9