Inheritance and characteristics associated with growth of the thickness of the nacreous elemental lamina of pearl oysters Pinctada fucata

Abstract

　Inheritance and seasonal variation of the thickness of the nacreous elemental lamina (TNEL) of shells of Akoya pearl oysters Pinctada fucata were investigated. Nine full-sib families were produced from two parental populations selected on the basis of three colors (red, green, and other) of shell nacre in May 2012. TNEL was estimated by measuring the maximum peak of the spectrophotometric reflectance wavelength for selected parents and offspring (at ages 14 and 16 months) at a hatchery. We analyzed the data to compare the mean TNEL values among families and the relationship between mid-parental values and mean values of the offspring. Also, seasonal fluctuations in TNEL and the relationship between TNEL and shell size and weight were observed in 2 families and in an additional 4 families (produced in March 2013) during a two-and-a-half-year period from 2013 to 2016. The results suggested that TNEL was significantly different between families. The TNEL of the parents had a strong positive correlation with the TNEL of the offspring. TNEL decreased as the shell grew and a negative relationship was observed between shell size or weight and TNEL in individuals during periodical long-term observation.