Effects of short-term starvation and refeeding on the survival, growth, and RNA/DNA and RNA/ protein ratios in rock carp (Procypris rabaudi) larvae

The ability of rock carp (Procypris rabaudi) larvae to resist and recover from starvation was examined by measuring their survival, growth rate, RNA/DNA and RNA/protein ratios during starvation and refeeding. At water temperature of (19.50.5)℃, sixteen days after hatching the larvae were randomly separated into six feeding treatments: a control treatment (food was always available) and treatments starved for 1, 2, 3, 4, and 5 days, and then refed. Whole experiment lasted for 10 days. wet weight (WW), body length, and contents of RNA, DNA and protein were measured in 9 Larvae from each treatment everyday. The results, in general, showed that survival and growth indicators above decreased as the starvation period increased. Larvae in all starvation treatments exhibited different extents of compensatory growth after refeeding. Larvae starved for 1, 2, and 3 days showed full compensatory growth that almost counteracted the effects of starvation and attained mean final WW similar to the control treatment. Larvae starved for 4 and 5 days showed partial compensatory growth that slightly abated the effects of starvation and their final WW was significantly different from the control. For larvae starved for 1-3 days and 4-5 days, it took 1-2 days and 4 days respectively, after refeeding to attain RNA/DNA ratios not significantly different from the control. Growth rates ranged from -0.59% to 8.00% WW/d and the regression equations between RNA/DNA and RNA/protein ratio and GR of larvae were GR=3.63RNA/DNA-1.74 (R2=0.80) and GR=120.14RNA/protein-2.33 (R2=0.31) respectively. The two ratios were significantly correlated with GR and RNA/DNA ratio fitted the growth variability better. Findings from the present study indicate that available food shortage is likely major factor to impair survival and growth during larval stage. The rock carp larvae were able to recover from less than 5 days of starvation. The RNA/DNA ratio was a more reliable indicator nutritional condition and growth in rock carp larvae.