Effects of Ca2+ and Mg2+ concentrations on growth,SOD and CAT enzymatic activity of juvenile Paralichthys olivaceus

Abstract:

The effects of Ca2+ and Mg2+ concentrations (1∶3) in artificial seawater on growth, superoxidase dismutase（SOD）and catalase（CAT） enzymatic activity of juvenile Paralichthys olivaceus were investigated at 20℃ and salinity of 30. Five concentrations of Ca2+ and Mg2+ were set as follows, 700 (group A), 1 100 (group B), 1 600 (group C), 2 200 (group D), and 2 800 (group E) mg/L, respectively. It was found that stress response occurred including bend of fish body and reduction of ventilation rate and food intake in juvenile fish under high Ca2+ and Mg2+ concentrations and the fish recovered after a week. After 60 d experiment, the survival rates of all groups were over 90%, and there were no significant differences in food conversion efficiencies (FCE) among different groups (P>005). However, the effects of Ca2+ and Mg2+ concentrations in artificial seawater on specific growth rates (SGR) and food intake (FI) at 0~20 d were significant (P<005). After 20 d, there was no significant difference in FI (P>005). During 40~60 d, the SGRs in low Ca2+ and Mg2+ concentrations groups were lower than that in high concentrations groups. The SGR and FI of all groups decreased when Ca2+ and Mg2+ concentrations increased. At 60 d, the SGR and FI of group A were 113 and 104 times as that of group E, respectively. Significant influences were also observed in immuno enzymatic activity of liver among these groups (P<005). The activity of SOD and hepatosomatic index of group D were significantly higher than those of other groups . However, the activity of SOD of group E was lower than other groups. The activity of CAT of group E was also lower than other groups but no significant difference (P>005). The results indicated that the concentrations of Ca2+ and Mg2+hindered the growth of juvenile P. olivaceus by changing their food intake. The fish in low Ca2+ and Mg2+ concentration groups grew fast and those in high Ca2+ and Mg2+ concentration groups grew slowly. There were no significant differences in the SGR of all the groups except for group E after 60 d rearing experiment. High Ca2+ and Mg2+ concentrations could restrain immuno enzymatic activity of juvenile P. olivaceus. It is suggested that high concentration of Ca2+ and Mg2+ should be avoided in the culturing of juvenile P. olivaceus.