Biological characteristics and muscle nutrition components analysis of three cultured populations of Pinctada maxima

【Objective】This study aimed to investigate the differences in external morphological characteristics and muscle nutrition components among different cultured populations of Pinctada maxima，providing a scientific basis for the classification，management and rational utilization of germplasm resources of P. Maxima from different geographical origins，and a theoretical reference for the management and protection of germplasm resources of wild P. maxima. 【Method】Cultured populations of P. maxima were collected from Beihai of Guangxi，Sanya of Hainan，and Xuwen of Guangdong. Their body weight，shell length，shell width，shell height and hinge length were measured. The nutrition components of muscle were detected，and the quality was evaluated according to the amino acid scoring model recommended by the Food and Agriculture Organization of the United Nations and the World Health Organization（FAO/ WHO）.【Result】The shell length，shell width，shell height and hinge length of Beihai（BH）population were all higher than those of Sanya（SY）population and Xuwen（XW）population. Except for body weight and shell width，other morphological traits of SY population were significantly lower than those of BH population and XW population（P<0.05，the same below）. The difference coefficient for all traits were less than 1.28，except for the shell width between the BH and XW populations（1.50），indicating that the morphological differences among the three cultured populations of P. maxima did not reach the subspecies differentiation level. Both principal component analysis and hierarchical cluster analysis showed that the distribution of the three populations was not completely separated and they overlapped with each other to some extent. The crude protein content of fresh muscle samples in XW population was significantly higher than that in BH and SY populations，but there was no significant difference in crude fat content （P>0.05）. A total of 17 amino acids were detected in the three populations，with the contents of aspartic acid（Asp），glutamic acid（Glu），glycine（Gly）and arginine（Arg）being the most abundant，accounting for 41.15%-45.56% of the total amino acids. The essential amino acid index（EAAI）of SY population was 73.23%，higher than that of BH population（64.48%）and XW population（45.53%）. A total of nine fatty acids were detected in the three populations，with α-linolenic acid being more abundant in the SY population，and oleic acid being more abundant in the BH and XW populations. No n-6 polyunsaturated fatty acids（n-6 PUFA）were detected in the muscles of the three populations，and only three kinds of n-3 polyunsaturated fatty acids（n-3 PUFA）were detected［eicosapentaenoic acid（EPA），docosahexaenoic acid（DHA）and α-linolenic acid］，with the highest content in SY population（0.0443%）.【Conclusion】P. maxima is rich in amino acids and has a balanced amino acid profile，making it a high-quality protein with high nutritional value. The comprehensive nutritional value of SY population is better than that of BH population and XW population.