COMBINED EFFECTS OF Cd2+ AND Zn2+ ON THE FERTILIZATION RATE IN PINCTADA MARTENSII (DUNKER)
Cd2+与Zn2+的联合效应对马氏珠母贝（Pinctada martensii）受精率的影响

Using the central composite face-centered design(CCF) and response surface methodology,the combined effects of Cd2+(0.030—20.000mg/L) and Zn2+(0.100—20.000mg/L) on the fertilization rate in Pinctada martensii were studied under laboratory conditions.The results showed that the effects of two factors Cd2+ and Zn2+ on the fertilization rate in P.martensii were highly significant(P<0.01),and effect of Cd2+ was more significant than that of Zn2+.The interaction between the two factors was also highly significant(P<0.01).Based on the response surface plots,it was found that with the increased concentration of Cd2+ and Zn2+,the fertilization rate was decreased.When Zn2+ concentration was at its lowest level(0.100mg/L),the fertilization rate decreased with the increased Cd2+ concentration.When Cd2+ concentration was at its lowest level(0.030mg/L),the fertilization rate was first decreased and then increased as the concentration of Zn2+ increased.The model equation of the fertilization rate towards Cd2+ and Zn2+ was established,with R 2 = 0.996,Adj.R 2 = 0.987 and Pred.R 2 = 0.887(P<0.01).The model equation could be practically used for forecasting the effects of Cd2+ and Zn2+ on the fertilization rate in P.martensii.