Research On The Desiccation Stress Tolerance And Stress Response Of Procambarus Clarkii

Procambarus clarkii is usually called crayfish,which is an important freshwater products in Chinese aquaculture because of its fast growth,mixed feeding habits,and strong reproductive capacity.Crayfish are mostly transported by anhydrous transport and often suffer from desiccation stress during transportation in the aquaculture production,which has a significant influence on the survival rate of transportation and culture benefits.The effects of desiccation on juvenile prawn,parent prawn and prawn with eggs were studied in this paper.The results are as follows: 1 Effects of desiccation with different temperature and humidity on mortality and water metabolism of juvenile prawnIn order to explore the dry tolerance of Procambarus clarkii under the different desiccation condition,four temperature gradient(16℃,20℃,24℃,28℃)were set respectively in normal humidity(50%~55%)and high humidity(90%~95%).The mortality,water loss percentage,body water content and weight consumption rate were measured.The results showed that the desiccation time of 20%~30% humidity group was the shortest(12h).The longest desiccation time of 50%~60% humidity group was 38 h at 16℃,and the shortest was 15 h at 28℃.Showing the trend that the higher the temperature,the shorter desiccation time.The water loss rate and body weight consumption rate of 90%~95% humidity group were the lowest,and the water content was the highest(P<0.05).The longest desiccation time of 90%~95% humidity group was 372 h at 16℃,which was the longest in all treatment groups,and the desiccation time was 10 times that of the other two humidity groups(P<0.05).While there was no significant difference in desiccation time bet-ween different temperature groups(P>0.05).The desiccation time of CS group was significantly higher than ZS group(P<0.05).Therefore,the desiccation tolerance of larvae was more affected by humidity,and the condition of high humidity was beneficial to larvae survive longer.2 Effect of desiccation and resubmersion on the oxidative stress response of the juvenile prawnIn order to study the effects of air-exposure stress on Procambarus clarkii during crayfish seedling transportation.The oxidative stress activities and survival rate response crayfish to desiccation stress(6 h,12 h,18 h,24 h)and resubmersed in water(1 h,6 h,12 h)were studied.The experiment conditions were 20±1℃ and 50±5% RH and which can indicate the health status of crayfish were preliminarily discussed.The results show that desiccation time is not suitable for more than 18 h,the mortality of 24 h group is 53.3%,while the the mortality of all the resubmersion group is 0%.There is no significant of air exposure stress on T-AOC activities are observed(P>0.05).However,the level of SOD significantly reduced,the CAT activities and contents of muscle lactate significantly increased with time,MDA content reach peak level after 24 h and the blood sugar content rise in the form of steps(P<0.05).There are fluctuating changes of SOD activities and CAT activities to adapt the stress and without obviously law during the resubmersion period,MDA content basically restored to the levels of normal after 12 h and the T-AOC maintain a high level during the resubmersion period.The lactate content of 6 h and 12 h groups restore to the levels after water entry for 1 h.The blood sugar content of all exposure groups are higher than that of the control group(P<0.05).The research shows that MDA content and SOD activities are more sensitive to the oxidative stress,which could be used as immune indexes.Blood sugar content and lactate cooperate with MDA content could be used synergistically to indicate the physiology of crayfish during the resubmersion period.3 Effect of desiccation and resubmersion on immune activity of parent prawnThe oxidative stress activities response crayfish Procambarus clarkii to resubmersed in water(1 h,4 h,7 h,10 h)were studied.The results showed that the contents of CAT and MDA in adult prawn,NO content in hemolymph of male individual were significantly higher than those in control group(P < 0.05),the levels of SOD and T-AOC in female individual decreased significantly(P < 0.05).The NO content of male individual was significantly higher than that of control group and female individual group during the resubmersion period(P < 0.05).The NO content of female individual increased firstly and then decreased with the time.The T-AOC levels of male and female decreased significantly after water entry for 4 h,while that of male individual basically maintained the level of control group.The CAT activity of male and female adult prawn was significantly higher than that of control group(P < 0.05),and the SOD activity returned to the level of control group after water entry for 10 h.The MDA content of adult prawn decreased gradually after water entry,and male individual returned to the level of control group after water entry for 10 h(P > 0.05).The results showed that NO content in haemolymph could be used as a health indicator to monitor crayfish,and the water inflow recovery ability of male crayfish was stronger than that of female crayfish.4 Effects of desiccation stress on hatching of prawn with eggsThe effects of air-exposure(6 h,12 h,24 h)on survival and hatching of crayfish were studied.The results showed that the survival rate of eggbearing crayfish was significantly affected by desiccation stress.When the time was 6 h,the survival rate of reentry water of egg-bearing crayfish was only 50%,which was significantly lower than that of the control group(P<0.05).While the survival rate of water entry in desiccation 24 hours group was 0.Desiccation stress had no significant effect on the incubation time(P > 0.05)compared with the control group,the incubation time was about 10-11 days.There was no significant difference in hatching number between the treatment groups and control group(P > 0.05).The hatching number of each desiccation groups ranged from 110 to 115 tails.The results showed that the desiccation time stress had no significant effect on the hatching of egg-bearing crayfish.Strictly controlled transportation time is the key to ensure the survival rate of water intake in the actual transportation of egg-bearing crayfish.