• pearl colour;
  • imaging and colour-measuring system;
  • host oyster;
  • donor oyster;
  • Pinctada martensii.


Cultured free round pearls are produced by implanting a spherical nucleus with a small piece of nacre-secreting mantle graft from a donor oyster into the gonad of a recipient oyster (host). To examine the possible contribution of host and donor oysters to the colouration of the harvested pearls, the CSE-1 Imaging and Color-Measuring System were used to quantitatively measure the L*a*b* values of donor and host shells and the produced pearls in Pinctada martensii. Results showed that the colour of pearls had significant positive correlation (r = 0.1–0.22, P = 0.00) with that of donors, but had no correlation with that of host oysters, thus convincingly confirmed the contribution of nacre colour of donor to the realization of pearl quality of colour. To further clarify the relationship between the donor and the pearl colour, the donors from pearls of good and poor colour quality were further compared and the results demonstrated the significant difference in L* values (P < 0.05) and insignificant difference in a* and b* values, suggesting the necessity of selecting donors with bright and lustrous nacre in pearl production.