Abstract: In order to explore the role of calmodulin（CaM）gene in the formation of freshwater mussel，Hyriopsis cumingii was cultured in water environment at 5 different Ca2+ concentrations of 0 mmol/L，0.5 mmol/L，1.25 mmol/L，2 mmol/L，and 3 mmol/L. At 0 d，20 d，50 d，90 d，and 120 d after nucleus inserted，mantle and visceral were sampled，then the CaM expressions in the tissues were detected using fluorescent quantitative PCR. The results showed that：1）The expression level of CaM gene in mantle and visceral mass were always low at 0 mmol/L Ca2+ concentration，decreased and then increased and remained stable at 0.5 mmol/L，decreased at the 20 d in visceral mass，then rose to level at 0 d and remain stable at 1.25 mmol/L，significantly increased at 20 d，reached the highest which was maintained at 2 mmol/L among all 5concentrations，increased at 20 d after nucleus inserted，and decreased in the later period（P < 0.05）at 3 mmol/L. 2）There was no obvious difference among different concentrations at 0 d，and the expressions differentiated along different days after 0 d. 3）Under the same culture conditions，the expression of CaM gene in visceral mass was higher than that in mantle. It was found that the concentration of 0.5 mmol/L and 2 mmol/L promoted the expression of CaM gene，but the concentration of 0 mmol/L and 3 mmol/L inhibited the expression of CaM gene. Visceral mass was more conducive to the formation of pearl.

Key words: Hyriopsis cumingii, calmodulin, calcium concentration, visceral mass, mantle