[Effects of starvation and re-feeding on survival rate, growth and digestive enzyme activities of juvenile Sepia pharaonis.]

To investigate the effects of starvation and re-feeding on survival rate, behavior, growth and digestive enzyme activities of juvenile Sepia pharaonis, the manipulative laboratory experiments were conducted with 0-6 days of starvation and 15 days of re-feeding to reveal the mechanism of compensatory growth. The results showed that starvation exerted a significant negative effect on the survival rate, growth, hepatosomatic index and digestive enzyme activities (P<0.05). The survival rate and digestive enzyme activities declined during the whole starvation process. After 3 days, the survival rate began to decline significantly, the decrease rate of body mass increased obviously and juveniles experienced some abnormal behaviors, such as inkjet, fighting and so on. The effects of starvation on digestive enzyme activities of juveniles were significant, and the digestive enzyme activities declined and then rose during the whole starvation process. The lowest amylase activity occurred after 4 days of starvation (0.07±0.02 U·mg ^-1 ·prot ^-1 ). The lowest lipase activity occurred after 2 days of starvation (18.47±2.07 U·g ^-1 ·prot ^-1 ), and the highest after 6 days (57.60±3.98 U·g ^-1 ·prot ^-1 ). The lowest pepsin and trypsin activities occurred after 5 days (1.98±0.59 U·mg ^-1 ·prot ^-1 ) and 4 days (186.68±20.72 U·mg ^-1 ·prot ^-1 ) of starvation, respectively. The effects of re-feeding on survival rate, growth, hepatosomatic index and digestive enzyme activities of juveniles were significant. The survival rate, specific growth rate, hepatosomatic index and feeding rate were negatively correlated with hunger processing duration. The survival rate, specific growth rate and hepatosomatic index showed no significant difference between 1 day starvation group and 2 days starvation group (P>0.05). The survival rate, specific growth rate and hepatosomatic index of 3 days to 6 days starvation groups were significantly lower than the control group. The feeding rates of 1 day and 2 days starvation groups were obviously higher than that of the control group. The feeding rate of 6 days starvation group was significantly lower than that of the control group. The amylase and lipase activities were not significantly different among different starvation treatments, whereas the pepsin and trypsin activities were significantly different, with the highest value in the control group (pepsin 7.06±0.64 U·mg ^-1 ·prot ^-1 , trypsin 914.67±26.54 U·mg ^-1 ·prot ^-1 ) and the lo-west value in the group with 6 days of starvation (pepsin 3.21±0.57 U·mg ^-1 ·prot ^-1 , trypsin 660.04±37.92 U·mg ^-1 ·prot ^-1 ). Six days of starvation would be the point of no-return for the juveniles, without any compensatory effect after starvation and re-feeding.