| A series of indoor trials were conducted to investigate the effects and mechanism of the salinity fluctuation on the molting, growth, feeding, food conversion, energy budget, plasma osmotic pressure, Na+-K+-ATPase activity and HSP70 in juvenile Fenneropenaeus chinensis. The primary results were listed below.1 Effects of salinity fluctuation on the molt rate,growth and energy budget of juvenile Fenneropenaeus chinensisExperiment was conducted to examine the effects of salinity fluctuation range on the molt rate and growth in juvenile Fenneropenaeus chinensis with the initial wet body weight of 1.427±0.086g. The salinity of the control treatment (S0) was 20ppt throughout the experiment, while treatments S2, S4, S6 and S8 were subjected to different salinity fluctuation, and the range was 2, 4, 6 and 8ppt, respectively. After the 30 days feeding trial, the molt rate of treatment S4 was 8.3% higher than that of treatment S0, while no significant differences of the molt rate of shrimp were existed among all five treatments. The specific growth rate (SGR) was SGRS4> SGRS2> SGRS6> SGRS0> SGRS8, and the SGR of treatment S4 was 8.6%, 9.0% and 10.7% obviously higher than that of treatment S0, S6 and S8 respectively (P<0.05); The feed intakes (FI) was FIS2< FIS4< FIS8< FIS6< FIS0. The feed intake of treatment S2 was significantly lower than that of treatment S0, while no significant differences were seen among treatment S4, S6, S8, and S0; The feed conversion efficiency (FCE) was FCES2> FCES4> FCES6> FCES0> FCES8, and the FCE of treatment S2, S4 was 13.6% and 12.3% higher than that of treatment S0 respectively (P<0.05). Allocation of energy used for growth of treatment S4 was higher than that of other treatments and was 12.1% higher than that of treatment S0 significantly (P<0.05), there were obvious differences of energy deposited for exuviae among all five treatments (P<0.05), while no significant differences of energy used for molt and feces existed among all five treatments (P>0.05). 2 The effects of salinity fluctuation amplitude on osmotic pressure,Na+-K+-ATPase activity and HSP70 in juvenile Fenneropenaeus chinensisExperiment was conducted to examine the effects of salinity fluctuation on the plasma osmotic pressure, Na+-K+-ATPase activity and HSP70 expression in juvenile Fenneropenaeus chinensis with the initial wet body weight of 1.442±0.030g. The salinity of the control treatment (S0) was 20ppt throughout the experiment, while treatments of S2, S4, S6 and S8 were subjected to different salinity fluctuation, and the range was 2, 4, 6 and 8ppt, respectively. After 30 days trial, plasma osmotic pressure decreased with the increase of salinity fluctuation range. Plasma osmotic pressure of treatment S6 and S8 was 3.3% and 5.5% significantly lower than that of treatment S0 respectively (P<0.05). In gills, Na+-K+-ATPase activity of treatment S6 was the lowest, while treatment S2 was the highest. There were insignificant differences in all five treatments (P>0.05). The same trend of Na+-K+-ATPase activity occurred in hepatopancreas. The HSP70 expression level increased with the salinity fluctuation range (D8 was slightly lower). HSP70 expression level of treatment S4, S6 and S8 was 48.4%, 48.2% and 40.6% higher than that of treatment S0 in muscle respectively (P<0.05). In eyestalks, HSP70 expression level of treatment S2, S4, S6 and S8 was 38.3%, 40.4%, 25.0% and 34.4% higher than that of treatment S0 respectively, and there were no significant differences among all five treatments (P>0.05). The better growth of shrimp might relate to the higher level of HSP70 expression under periodic salinity fluctuation.3 Effects of salinity fluctuation frequency on the molt,growth and energy budget in juvenile Fenneropenaeus chinensisExperiment was conducted to examine the effects of salinity fluctuation on the molt rate, growth and energy budget in juvenile Fenneropenaeus chinensis with the initial wet body weight of 1.114±0.017g. The salinity of the control treatment (D0) was 28ppt throughout the experiment, while treatments D2, D4, D6 and D8 were subjected to different salinity fluctuation, and the frequency was 2, 4, 6 and 8 days, respectively. After the 32 days feeding trial, the molt rate of treatment D2, D4, D6, D8 was 12.8%, 14.9%, 15.5% and 13.4% respectively, and the molt rate of treatment D4 was 12.9% higher than that of treatment D0, and treatment D6 was 17.4% higher than that of treatment D0 significantly (P<0.05). The specific growth rate (SGR) of treatment D4 was 3.79?%-1?d-1 which was obviously higher than that of other treatments (P<0.05). The feed intakes (FI) was D6> D0> D2> D4> D8, and there were no significant differences. The feed conversion efficiency (FCE) of treatment D2, D4, D6 and D8 was 6.1%, 26.9%, 3.7% and 10.2% higher than that of treatment D0 respectively, and there were obvious differences between treatment D4 and D0 (P<0.05). Allocation of energy used for growth of treatment D2, D4, D6 and D8 was 6.7%, 25.6%, 1.2%, 9.5% higher than that of treatment D0, and there were obvious differences between treatment D4 and D0 (P<0.05). The energy used for molt of treatment D4, D6 and D8 was 22.4%, 33.9% and 21.9% higher than that of treatment D0, and there were obvious differences between treatment D6 and D0 (P<0.05). There were significant differences among treatments with the energy used for respiration and excretion (P<0.05), but the obvious differences were not found with the energy used for feces.4 The effects of salinity fluctuation frequency on osmotic pressure,Na+-K+-ATPase activity and HSP70 in juvenile Fenneropenaeus chinensisExperiment was conducted to examine the effects of salinity fluctuation on the plasma osmotic pressure, Na+-K+-ATPase activity and HSP70 expression in juvenile Fenneropenaeus chinensis with initial wet body weight of 1.460±0.091g. The salinity of the control treatment (D0) was 28ppt throughout the experiment, while treatments D2, D4, D6 and D8 were subjected to different salinity fluctuation, and the frequency was 2, 4, 6 and 8 days, respectively. After 32 days trial, the plasma osmotic pressure of treatment D2, D4, D6 and D8 was significantly lower than that of treatment D0 (P<0.05). The Na+-K+-ATPase activity level of salinity fluctuation treatments were insignificantly differences with the control treatment both in gills and in hepatopancreas (P>0.05). HSP70 expression level of salinity fluctuation treatments were higher than that of the control treatment. HSP70 expression level of treatment D4 was 61.3% and 57.0% higher than that of treatment D0 significantly both in muscle and eyestalks (P<0.05). The better growth of shrimp might relate to the higher level of HSP70 expression under periodic salinity fluctuation.5 Effects of salintiy fluctuation frequency on the change of ecdysteriods extent in juvenile Fenneropenaeus chinensisExperiment was conducted to examine the effects of salinity fluctuation on the ecdysteriod extent in juvenile Fenneropenaeus chinensis with the initial wet body weight of 2.038±0.061g. The salinity of the control treatment (D0) was 28 throughout the experiment, while treatments D2, D4, D6 and D8 were subjected to different salinity fluctuation, and the frequency was 2, 4, 6 and 8 days, respectively. The ecdysteriod extent of shrimp kept low level and increased gradually in intermolt period, and increased rapidly and reached peak value in premolt period, then decreased suddenly and the lowest level occurred in postmolt period. In postmolt period, the ecdysteriod extent of treatment D2 was significantly higher than that of treatmen D0, D6 and D8 (P<0.05), but there were no significant differences between treatment D2 and D4 (P>0.05). There were no significant differences of ecdysteriod extent among all five treatments in intermolt period (P>0.05). The ecdysteriod extent of treatment D6 was the highest and was 17.6% significantly higher than that of treatment D0 (P<0.05), while treatment D2 was significantly lower than that of other treatments (P<0.05).
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