Influence of Age on Pearl Production Performance, Enzymatic Activity, and Immune-Related Gene Expression of the Pearl Oyster Pinctada fucata martensii

This study evaluated the influences of age on the pearl production performance and innate immune responses of the pearl oyster Pinctada fucata martensii. Two age-groups (group A: 1.5 years of age; group B: 2.5 years of age) were subjected to a nucleus insertion operation. The immune- and antioxidant-related enzymatic activities and expression levels of immune-related genes in both groups were evaluated 3 d after the nucleus insertion operation. The survival rate, retention rate, and biomineralization capacity of the groups were examined when the pearls were harvested. The results showed that the activities of alkaline phosphatase, acid phosphatase, superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) and the expressions of the SOD, GPx, heat shock protein 70 (HSP70), and HSP90 genes were significantly higher in group A than in group B 3 d after the nucleus insertion operation (P < 0.05). Group A had a significantly higher survival rate than group B at 3, 7, and 30 d after the operation and at harvest. Group A had a significantly higher retention rate and pearl thickness than group B at harvest. The expression levels of the biomineralization genes for nacrein and pearlin were significantly higher in group A than in group B (P < 0.05), whereas expression of the biomineralization gene for Pif-177 was significantly higher in group B. Collectively, these results suggested that 1.5-year-old pearl oysters have better pearl production performance and innate immune response to nucleus insertion operations, so selecting young pearl oysters to use as host and donor oysters shows promise as a process for improving the quality of cultured pearls.