Pinctada margaritifera mollusc is
cultivated in French Polynesia for the production of black pearls.
For this study, the colour of juvenile samples (48 days old) was
investigated in the visible range spectra (430–700 nm) using spectrophotometry.
A first measurement was done with the soft parts still inside the
shell (entire animal). Then, the soft parts were removed in order
to do a second measurement on the growing edge of the shell. Comparison
of the two measurements shows that the estimation of the living
animal colour with unaided eye is strongly influenced by the colour
of the soft parts. The use of the International Commission on Illumination
(ISI) chromaticity diagram shows that at this growth stage, the
shells are “white”; i.e. present no absorptions to the visible part.
Multivariate statistical analyses based on the intensities of 6 wavelengths
show that the shell colour is less variable than the colours of
the entire animals. Wavelength intensities of the shells are similar,
so no colour trend is visible. On the other hand, the colours of
the entire animals are darker, and more variable. At this growth
stage, the shell colour is not predictable for a potential selection
of receiver or donor.