The effects of different Ca 2+ concentration fluctuation on the moulting, growth and energy budget of juvenile Litopenaeus vannamei (Boone)

A 40-day experiment was conducted to investigate the effects of different Ca2+ concentration fluctuation on the moulting, growth and energy budget of juvenile Litopenaeus vannamei with an initial wet body weight of (1.20 +/- 0.01) g. The Ca2+ concentration of the control group C385 was 385mg L-1 throughout the experiment, while the Ca2+ concentration of the C591, C803, C1155 and C2380 groups periodically fluctuated from 385 to 591, 803, 1155 and 2380 mg L-1 respectively. The moulting frequency (MF) of the shrimp in the Ca2+ concentration fluctuating groups was significantly higher than those in the control group (P<0.05). The specific growth rates (SGR(d)) and feed intake of the shrimp in the C591 and C803 groups were significantly higher than those in other groups (P<0.05), but no significant differences in feed efficiency were found among all groups (P>0.05). The shrimp in C591 and C803 groups spent significantly less energy in respiration, while depositing significantly more energy for growth than those in other three groups (P<0.05). These results showed that proper Ca2+ concentration fluctuation could increase the MF and growth rate of the juvenile L. vannamei, and according to the regression formula made using SGRd and range of Ca2+ concentration fluctuation, periodically enhanced Ca2+ concentration of 295 mg L-1 in the seawater was suggested to be used in shrimp culture.