First characterization report of natural pearl of Pinctada fucata from Gulf of Mannar

The present study is aimed to characterize the natural pearl of Pinctada fucata from Gulf of Mannar by Scanning Electron Microscope (SEM) and Energy Dispersive Studies (EDS). Pearl oysters (P. fucata) from Kayalpattinam, Gulf of Mannar, were landed as a by-catch in the bottom set gill net at a depth of 4 m and collected for tissue culture studies. During mantle tissue dissection, a good lustrous, round pearl of 1.5 mm size was found in the mantle fold of pearl oyster P. fucata. This evidenced the existence of natural pearl oyster beds and natural pearls in this region. It was analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to find out the composition of nacre. Parallel orientation of crystals to form the lamellar formation of nacre is clearly visible in SEM. Pseudo-hexagonal aragonite crystals arranged in a uniform layer and joined together to form a lamella with inter-lamellar matrix. Two forms of calcium (CaO and CaCO₃) obtained in EDS analysis. Calcium content in the natural pearl is 66.05% which is clearly reveals the aragonite form. Niobium (Nb) was attained at 6% in natural pearl which is the first report in its kind and it may also play a role in the formation of lustrous layer. There are so many characterization reports available about mother of pearl in shell of different species, but this is the first report of natural pearl from P. fucata.