| The Red claw crayfish(Cherax quadriarinatus)is a large freshwater precious shrimp which is similar to lobster.It has high ornamental value because of its beautiful appearance.Therefore,body color is one of the key traits that affect the value of C.quadricarinatus.The body color of aquatic economic animals is not only regulated by genetic material,but also affected by environment and food.The body color change of C.quadricarinatus is also the result of the interaction of the three factors.However,there is little research on the change of body color of red claw crayfish at present.This study(1)compared the differences of growth,body color and high temperature tolerance between two kinds of C.quadricarinatus with stable body color heredity;(2)studied the effects of background color,p H and diet on the growth and body color of C.quadricarinatus with normal body color.The results are as follows:There are differences in the growth performance,carotenoid content and heat resistance of C.quadricarinatus with blue and brown-green shell colors.(1)After 56 days of feeding,The PWG(145.18)of blue C.quadricarinatus group was significantly higher than that of the brown-green C.quadricarinatus(121.05)(P<0.05).The survival rate was only 65%,which was significantly lower than that of brown green crayfish(72.5%);(2)The astaxanthin content in the blue C.quadricarinatus is 18.62 mg/kg wet weight,which is significantly lower than that in brown-green C.quadricarinatus(83.23 mg/kg wet weight);(3)The survival rate of the two kinds of C.quadricarinatus was 100%after 7 days of culture at the temperature lower than 34℃.When the temperature rose from 35℃to 38℃,the survival rate of the brown-green C.quadricarinatus was higher.(4)After acute heat stress,superoxide dismutase(SOD)activity of C.quadricarinatus in brown-green group was 74.67U/mg prot at 6h,which was significantly higher than that of C.quadricarinatus in the blue group(61.72 U/mg prot)(P<0.05).CAT activity of C.quadricarinatus in the brown-green group was 1.40,6.49 and 8.77 U/mg prot at 0,3 and 6h after stimulation,respectively protein,which was significantly higher than that in blue group(1.07、4.79、4.45 U/mg prot)(P<0.05),but there was no difference in total antioxidant activity(T-AOC)and malondialdehyde(MDA)content between the two groups.In conclusion,the Blue C.quadricarinatus has better growth performance and more beautiful body color,but its tolerance to high temperature is poor.2.In order to explore the effects of different background colors on the growth and body color of C.quadricarinatus.The effects of five different background colors(white,red,green,blue and black)on the growth,survival,body color and habitat behavior of C.quadricarinatus were compared.The results as follows:(1)After 56-day of rearing period,C.quadricarinatus of black background group showed the highest increase in body weight,specific growth rate and survival rate(32.66g,1.74%and 76.4%),followed by the green,blue and red background groups,and the white group was the lowest(P<0.05);(2)The feed coefficient of black and red background C.quadricarinatus was the lowest(3.73-3.80);(3)The body color of C.quadricarinatus reared in black condition was showed bluer than other groups.Image J analysis showed that the R and G values of black background group were significantly lower than those in other groups;(4)The content of astaxanthin in the black group was 20.233 mg/kg,which was significantly lower than other groups(69.338-82.152mg/kg)(P<0.05);(5)the probability of C.quadricarinatus distribution outside the shelter was significantly higher in black background group than that in other groups(P<0.05).The results show that background color can significantly affect the growth,survival,body color and behavior distribution of C.quadricarinatus.It would be helpful for improve the growth and survival rate,as well as body color,of C.quadricarinatus under black background.3.The effects of p H 6.0,7.0 and 8.5 on growth,survival,body color and environmental stress kinase activities of C.quadricarinatus were compared.The results showed that:(1)After 56 days of culture,the weight gain,specific growth rate and survival rate of crayfish reared in p H 8.5 were the highest(19.18g,2.12%and 85%,respectively),followed by in p H7.0 and 6.5,and significant differences were observed among different streatments(P<0.05);(2)The body color of crayfish at p H 6.5 was yellow,while brown green and dark blue body color were observed at p H 7.0 and 8.5,respectively.RGB analysis by Image J showed that the R value of crayfish at p H 6.5 was the highest(53.59),and the B value was the lowest(23.12),while the R value crayfish at p H 8.5 was the lowest(42.24),and the B value was the highest(41.95).There was significant difference in R and B values between these two groups(P<0.05);(3)The astaxanthin content reared at p H 6.5(49.166 mg/kg)was significantly higher than that at p H 7.0(32.827 mg/kg)and 8.5(26.369 mg/kg)(P<0.05);(4)The activities of SOD and CAT in hepatopancreas of crayfish reared at p H 7.0 were the lowest,which were 30.01 U/mg prot and 0.66 U/mg prot,respectively,and significant differences were found in the activities of SOD and CAT,compared to other two treatments(P<0.05),while the activity of T-AOC at p H 8.5 was 0.20 mmol/prot,which showed significantly higher than that at p H 7.0 and 6.5(P<0.05);(5)Furthermore,the activities of Na~+K~+-ATP in gill at p H 6.5 were the highest(7.41 U/mg prot),followed by at p H 8.5(4.19U/mg prot)and p H 7.0(1.92 U/mg prot),and there were significant differences among different treatments(P<0.05).In conclusion,the growth,survival,body color and environmental stress kinase activities of crayfish are related to p H.During culturing process,it is more conducive to the growth and survival of crayfish at p H 8.5,and blue individuals could be cultivated.4.In order to explore the effects of different diets on the growth,survival and body color of C.quadricarinatus of different sizes,the effects of four diets-formula feed(FF),papaya 50%+formula feed 50%(PMFF),tilapia meat 50%+formula feed 50%(TMFF),and papaya 25%+tilapia meat 25%+formula feed 50%(PTMFF)-on the growth,survival and body color of C.quadricarinatus(0.51g,10.51g and 30.70g)were studied.The results showed:(1)As for the small size group,the TMFF group had the largest body weight increase(10.81g±1.20g)and the highest specific growth rate(5.47±0.11),which were significantly higher than the body weight increase and growth rate of the other groups(P<0.05),and the survival rate was 100%among all groups.(2)As for the medium-sized group,the PTMFF group had the largest weight gain(23.70±1.32g)and specific growth rate(2.11±0.08),which were significantly higher than the weight gain and growth rate of the other groups(P<0.05),and the survival rate of TMFF group is the lowest and significantly lower than that of the other groups(P<0.05).(3)As for the large size group,PMFF group had the highest weight gain(27.96±0.94g)and a specific growth rate(1.16±0.13),which were also significantly higher than the weight gain and growth rate of the other groups;(4)The group with the deepest body color of red claw crayfish of all sizes was PWFF group with the lowest L value(12-16),which was significantly lower than that of other groups.The content of astaxanthin in shrimp shell was 84.64 mg/kg-87.12 mg/kg,which was significantly higher than that of other groups(P<0.05).To sum up,C.quadricarinatus has different preferences for food on different growth stages.Feeding with different proportion of feed in different growth period can achieve a better growth rate,survival rate and body color. |
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