Effects of β-carotene supplement in bait on inner shell color, tissue total carotenoids content and growth of different color strains in Hyriopsis cumingii

Pearl and nacre share a similar mechanism of formation. It has been found that there is a significant correlation between the color of pearl and that of nacre. In this study, three stains of Hyriopsis cumingii in purple, golden and white were examined. Experimental groups and control groups with supplementation of β-carotene were set up. After 90 d of cultivation, the color of nacre of the three stains, total carotenoid content (TCC) of their organs, and their changes in growth were compared and analyzed. The results show that compared with the control group, for purple H. cumingii, the dE value increased by 21.48% (P<0.05); L^* value decreased by 15.72% (P<0.05); a^* value increased from 0.48 to 2.67 (P<0.05) and there was no significant change in b^* value (P>0.05). For golden H. cumingii, the a^* and b^* values increased from 0.07 to 1.52 and from 1.37 to 4.43, respectively (P<0.05), and there was no significant change in the dE and L^* values (P>0.05). For white H. cumingii, there was no significant change in any of the parameters (P>0.05). The hepatopancreas TCCs of the experimental groups of the three color stains were greater than those of the control groups (P<0.05). Compared with the control group, for purple and golden H. cumingii, the TCCs of edge mantle increased by 55.29% and 39.69%, respectively (P<0.05), while for white H. cumingii, there was no significant change (P>0.05). All the growth traits of the three color strains were larger than those of the control groups (P<0.05). The results confirm that supplementing β-carotene can enhance the color of nacre and growth of H. cumingii, which provides a theoretical basis for optimizing the pearl culture technology.