CALCIUM METABOLISM IN HYRIOPSIS CUMINGII DURING EARLY PEARL-FORMING STAGES
三角帆蚌(Hyriopsis cumingii)珍珠形成初期钙代谢的特征分析

Post-implantation Hyriopsis cumingii was studied for 57 days, to investigate calcium metabolism during early pearl-forming stages. The samples were taken every week, the values of diameters and weights of pearl-sac and pearl, temperature of water, calcium contents and specific activities of acid phosphatase and alkaline phosphatase of mantle, gill and heart, and gene expression of calmodulin in mantle were measured. The diameters and weights of pearlsac or pearl in H. cumingii increased with the increase of water temperature, periods of obviously rapid growth appeared at day 22 and 43, respectively. The specific activities of acid phosphatase and alkaline phosphatase were the highest in the mantle, and the lowest in the heart. The specific activity of acid phosphatase in mantle and gill reached the peak at day 8, and then decreased gradually. The specific activity of alkaline phosphatase in mantle reached the peak at day 15, maintained at similar levels until day 29, and then decreased gradually; in contrast, the enzyme specific activities in gill and heart increased after day 15, and reached the peak at the day 29. The calcium contents of mantle, gill or heart increased; the calcium content of gill was the highest and reached the peak at day 43. The RNA expression of calmodulin in mantle were enhanced significantly after implantation, especially at day 8 and 43. It is suggested that primary pearlforming in H. cumingii mainly depended on the calcium metabolism in gill and mantle. Acid phosphatase, alkaline phosphatase, and calmodulin all played important roles. The relevant metabolic events probably follows the order of up-regulation of the gene expression of calmodulin, activation of acid phosphatase and alkaline phosphatase, and the increasing of calcium contents in mantle and gill, leading to pearl growth. Day 8, 15 and 43 after implantation were the key stages of pearl-forming.