On pearl formation in the venerid bivalve, Gafrarium tumidum Roding

Abstract

Bolman (1941) in his work ' The Mystery of the Pearl ' has elaborately dealt with all aspects of the pearl as the pearl producing molluscs, the structure of the pearl, its classification, chemical composition, culture, pearl fisheries of the world, the fossil pearls and the vegetable pearls. The marine lamellibranchs, gastropods, and freshwater bivalves of the superfamily Unionaceae are known to produce pearls in nature. Among these, the species under the genus Pinctada Roding are well known -as the gem pearl producing molluscs and welI-established and traditional fisheries exist for these species in some parts of the world. Other marine bivalve molluscs from which pearls have been obtained are Modiolus, Mytilus, Malleus, Pinna nigra, P. squamosa, P. nobilis, Placuna placenta, Tridacna gigas, Venus margarifia and Ostrea edulis (Bolman, 1941 ; Alexander, 1951 ; Cooke, 1959). Other genera which do not possess any mother-of-pearl layer, but in which sometimes po~(x1lanous pearls are found are Spondylus, Pecten, Anomia, Cytherea, Lutraria, Tellina, Mya,) Hippopus, Solen, Arca and Glycymeris (Bolman, op.cit.). The present communication records a case of pearl formation in the bivalve species, Gafrarium tumidum Roding.