Compensatory Growth Response Following Starvation In Juvenile Of Megalobrama Pellegrini

Megalobrama pellegrini,because of its high economic value and better growth performance, and due to the loss of habitat the population sizes of Megalobrama pellegrini decreased sharply,is become one kind of important breeding species gradually.Now,many researches focus on the biological characterization,life history type,disease control and artificial breeding,but studies on its starvation physiology have not been conducted.In this experiment,the effects of starvation and refeeding on the compensatory growth,the activity of digestive enzymes(including protease,lipase and amylase),the DNA,RNA contents and RNA/DNA ratio,feeding and growth,the biochemical composition were investigated.The tested Megalobrama pellegrini were divided into 5 experimental groups,each group having 3 replicates,and seting another group for starved sample. The fish were starved of food for 0day(control group,S0),2days(S2),4days(S4),7days(S7) and 14days(S14),then the fish of each group were refed(fed to satiation) for 28days,26days,24days, 21days and 14days.Test the bodyweight,the biochemical composition,the activity of digestive enzymes and the DNA,RNA contents,RNA/DNA ratio of the fish through measuring the samples of each group.The experimental results are shown as follows:1.Before starvation the body weight of fish was no significant difference(P＞0.05),after hungry processing,the fish body weight is dropping unceasingly along with the starved time extension.But each starved group not showed remarkable difference(P＞0.05).Body weight loss of starved 7days and 14days group was significantly greater than the starved 2days and 4days group(P＜0.05).Upon refeeding,the conversion efficiency of starved fish was higher than the control group, except the S14 group was significantly lower than the S0 group(P＜0.05).The specific growth rate of starved fish was significantly higher than the fed fish(P＜0.05).At the end of the experiment,the body weight of the fish of S2,S4 and S7 group was similar to that of fed fish(S0 group),and the fish of group S14 was significantly lower than the fed fish(S0 group)(P＜0.05).So we know that after recovery feeding,the fish deprived of food for 2days,4days and 7days got completely compensatory growth;the fish deprived of food for 14days got partially compensatory growth.The result suggests that the mechanism of compensatory growth in juvenile of Megalobrama pellegrini be due to the higher feeding rate and conversion efficiency after starvation.2.During starvation contents of moisture and ash increased step by step,but contentsnof glycogen,crude lipid and protein descended.During early starvation,the content of glycogen and crude lipid dropped markedly,but the change of crude protein was not significant.Later of starvation,it was changed,the content of crude protein dropped markedly that in the group of starved 14days.The results indicated that juvenile of Megalobrama pellegrini used glycogen as their energy origin firstly during starvation,and then used crude lipid,at last used the crude protein as energy.After recoveery feeding,the biochemical composition and glycogen were compensated to the level of fed fish.3.Along with starved time extension,the activity of trypsin enzymes and lipase enzymes in the liver and gut dropped,but the amylase activity has first raised and then droped again.During early starvation,the activity of trypsin enzymes and lipase enzymes desended markedly.At the 2day of starved it stepped down sharply.Later of starvation,trypsin enzymes and lipase enzymes desended slowly.Upon feeding,the acticity of digestive enzymes in the starved group rose quickly, and when the experiment ended,the enzymes all resume to the level of control group except the starved 14day group.4.With the prolonging of starvation,DNA content in the liver and muscle is elevating gradually,the contents of RNA and RNA/DNA ratio reduces gradually.Upon refeeding,contents of DNA,RNA and RNA/DNA ratio present different change rule.The content of DNA in each starved group resumed to the control group level,except the muscle of starved 14day group.The content of RNA in each starved group resumed to the control group level,except the starved 14day group.The starved 2day and 4day group's RNA/DNA ratio exceed the control group,and RNA/DNA ratio in the liver of starved 7day group upto control level when refeeding 12days.But the muscle of starved 7day and starved 14day group not upto control level until experiment eneded.