| The progress of endocrinology of the crustacean molting, environmental factors and nutritional factors that influence molting is summarized in this paper,it also descripts the physiological response of the crustacean's osmotic pressure and respiration after the a salinity mutation.The aim is to provide a reference for doing researches and guiding practices in this field.1. Effects of four kinds of salinity fluctuations on the synchrony molting of juvenile Litopenaeus vannamei is studied when the salinity is 18.The experiment is conducted in a cement pond(33 m2). The initial body length of the experimental shrimp is 4-5cm.The group that the salinity is 18 is considered as control (signed with S0),the other 4 groups which have different salinity fluctuations which are 2,4,6,8,are signed with S2,S4,S6 and S8, respectively.Each group has two parallels and the experiment lasts 30 days.The results shows that the group of S4 has the largest number of shrimp molting during the whole experiment, the group of S8 has the most days between the high molting rate and the low molting rate,besides, its number of molting that has a high molting rate takes up the largest proportion of the total number of molting. The group of S8 has the best synchronization of molting,then is S2,S4,C and S6, ordinarily.2. Effect of different salt-decreasing times on synchrony molting of shrimp Litopenaeus vannamei Boone is studied. In laboratory, shrimps (with wet weight of 3.63±0.76g) are reared at 18 ppt (control), the salinity was decreased on day 3,5,7,9 (labeled as D3,D5,D7,D9) at a rate of 4 ppt. The period of salinity fluctuation was 10 days. After a 50-day experiment, we found that treatment D9 had the most molting frequency, which was followed by the treatment D5, D3, D7 and the control. Treatment D3 had the best synchrony molting, treatment D9, D5, D7 and the control followed. 3. This study deals with the effect of rhythmic addition of calcium to the sea water on synchrony molting of shrimp Litopenaeus vannamei Boone. There were 5 treatments with different Ca2+concentration, that were 591,803,985,1155 and 2380 mg/L (labeled as C600, C800, C1000, C1200 and C2400), normal sea water with a Ca2+concentration of 385 mg/L as control. The results indicated that, treatments except C2400 all had higher molting frequency than control. C800 had the highest one, and C600 had the best synchrony molting, treatment C1200 and C800 followed.4. This study deals with the effect of rhythmic change of light color on synchrony molting of shrimp Litopenaeus vannamei Boone. There were 3 groups of constant light color, yellow, green and blue (labeled as Y, G and B),3 groups of rhythmic change of light color, blue to yellow, blue to green and green to yellow (labeled as BY, BG and GY). The photoperiod was 14 h light:10 h dark, and the illumination was controlled at 300 lx. After a 40-day experiment, we found that group BG had the highest molting frequency, which was followed by group GY, G, Y, BY and B. Group G had the best synchrony molting, then group B, YG, BY, Y and BG followed.5. This paper was conducted to investigate the effects of salinity fluctuation on the molt, oxygen consumption rate, ammonia-N excretion rate and urea-N excretion rate of juvenile Litopenaeus vannamei with initial wet body weight of (2.485±0.303)g. The salinity of the control treatment (C) was 29 throughout the experiment, while treatment S2, S4, S6 and S8 groups were subjected to different salinity fluctuation and the range was 2,4,6 and 8, respectively. Each treatment group had 10 replicates. The salinity was declined at Stage D1 of the shrimp, then samples were taken at different time. The salinity was increased to 29 at the 97th hour, and re-sampled. The entire experiment was lasted 7 days. The test shrimps in treatment S4, S6 and S8 groups molted for one day ahead of schedule after salinity decrease, and more concentrative molt was occurred in S6 treatment. The oxygen consumption rate of the test shrimps showed a decrease trend firstly, and increased gradually with the arrival of the molt stage in treatment C, S4, S6 and S8 groups. The oxygen consumption rate of treatments C and S4 were significantly lower than those at the 96th hour after the salinity increase. Ammonia excretion rate of the test shrimps also presented a decrease trend after the salinity fluctuation (except treatment S8). The urea-N excretion rates of the test shrimps in treatment S2, S4 and S6 groups were relative stable after 24 hours of salinity decrease. And the peaks of the oxygen consumption rate, ammonia excretion rate and urea-N excretion rate in treatment C and S8 groups occurred and coincided with the molt peak during the experiment.6. This paper was conducted to investigate the effects of salinity fluctuation on the hemolymph osmotic pressure, hemocyanins, blood glucose,HK and PK of juvenile Litopenaeus vannamei with initial wet body weight of (2.485±0.303)g. The salinity of the control treatment (C) was 30 throughout the experiment, while treatment S2, S4, S6 and S8 groups were subjected to different salinity fluctuation and the range was 2,4,6 and 8, respectively. The salinity was declined at Stage C of the shrimp, then samples were taken at different time. The salinity was increased to 30 at the 97th hour, and re-sampled. The entire experiment was lasted 7 days. The hemolymph osmotic pressure of the test shrimps showed a decrease trend in treatment S2, S4 and S6 groups after salinity decrease, and increased after the salinity increase. The hemocyanins of the test shrimps showed a decrease trend firstly, and increased gradually in treatment S4, S6 and S8 groups after salinity decrease, and decreased in S4 and S6 group after the salinity increase. The blood glucose of the test shrimps showed a decrease trend firstly, and increased gradually,then decrease again in treatment S4,but in S6 and S8 group was increased rapidly after salinity decrease,and decrease gradually. The HK activity in hepatopancreas showed a decrease trend firstly, and increased gradually in all treatment groups after salinity decrease,and inceased in 24h afer the salinity increase. The PK activity in hepatopancreas had difference only in S6 and S8 group.
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