Inheritance of White Coloration of the Prismatic Layer of Shells in the Japanese Pearl Oyster Pincada fucata martensii and its Importance in the Pearl Culture Industry

Abstract

Breeding experiments revealed that the white coloration of shell (prismatic layer) of the Japanese pearl oyster is inherited under the control of a recessive gene. Three matings were made: in two of them white female mated to white male in the other white female with brown (most common type) male. All the offsprings from the matings with white parents had the white coloration of prismatic layers with the few exceptional brown type which might have been introduced accidentally from other matings. Meanwhile only brown type of shells were obtained from the cross of white female × brown. The ratio of 3: 1 in brown and white specimens were obtained from F2 of the last mating. These are expected ratios in crosses of brown heterozygous and white homozygous for a simple Mendelian character and it was estimated that the white coloration may be inherited under the control of recessive gene. Preliminary observation of the pearl layer (nacre) showed that the amount of yellow pigments seemed smaller in white specimens than in brown ones. The former would be useful for the production of pearls without yellow pigments that are less valuable than others although the shells were heavier in the brown specimens than in the white one. © 1990, The Japanese Society of Fisheries Science. All rights reserved.