| In order to solve the technical problems in crayfish farming,such as the low efficiency of intensive seedling production caused by the present breeding mode,the difficulties in achieving the unification of large-scale artificial breeding and parent shrimp cultivation quality,the asynchronous holding of eggs,and the abnormal hatching of embryos caused by the death or abandonment of eggs during parent shrimp cultivation,experiments were conducted to investigate(1)Effects of feeding astaxanthin-enhanced black soldier fly(Hermetia illucens)larvae on the growth,body color,egg holding rate and antioxidant capacity of redclaw crayfish(Cherax quadricarintus);(2)Effects of replacement diet of black soldier fly larvae and different treatments of soybean on growth,digestive physiology,intestinal tissue structure and intestinal flora structure of juvenile crayfish;(3)Effects of different treatments of soybean on the growth,digestive enzyme activity and intestinal flora structure of juvenile redclaw crayfish;(4)Effects of in vitro incubation on embryonic hatching rate and total bacterial count of crayfish;(5)Morphological and transcriptome analysis of sex reversal redclaw crayfish.The results are as follows:1.Feeding astaxanthin enhanced the effects of black soldier fly larvae on growth,body color,egg holding rate and antioxidant capacity of crayfish.Adult shrimps with body length of 83.5 ± 8.39 mm and body weight of 25.56 ± 7.46 g were divided into four groups: group A,group B,group C and group D.They were fed with shrimp feed and 0,50 and 150 mg / L astaxanthin-enhanced black soldier fly larvae,respectively.The feeding experiment lasted for 40 days.The results showed that astaxanthin had no significant effect on the growth of crayfish.The body color brightness values of group C and group D were significantly higher than those of group A and group B(P<0.05);the total antioxidant capacity of group D was significantly higher than the other three groups(P<0.05).2.Effects of replacement of compound feed by black soldier fly larvae on growth,digestive physiology and intestinal tissue structure of juvenile redclaw crayfish.The crayfish larvae with body length of 37.77 ± 5.27 mm and body weight of 2.10 ± 0.66 g were divided into groups A,B,C,D and E.The proportions of feeding black fly larvae to replace compound feed were 0,25 %,50 %,75 % and 100 %(according to the wet weight of fresh larvae),respectively,and the culture lasted for 40 days.The results showed that the relative growth rate,weight gain rate,specific growth rate and hepatopancreas index of shrimp in each group increased first and then decreased,and the relative growth rate and specific growth rate of group C were significantly higher than those of group E(P<0.05).The hepatopancreas index of group A,B,C and D was significantly higher than that of group E(P<0.05).With the increase of larval replacement feed ratio,the trypsin activity of shrimp in each group increased gradually,and the lipase activity increased first and then decreased.The highest lipase activity in group B was 0.70 ± 0.18 U / gprot.The intestinal wall thickness and intestinal villus height of juvenile redclaw crayfish in each substitution group were significantly lower than those in the control group(P<0.05).With the increase of substitution ratio,ammonia nitrogen and nitrite in each group of aquaculture water decreased.3.Effects of different treatments of soybean on the growth,digestive enzyme activity and intestinal microflora of juvenile redclaw crayfish.The crayfish larvae with body length of 48.21 ± 1.86 mm and body weight of 4.61 ± 0.36 g were divided into five groups A,B,C,D and E,and fed with compound feed,raw soybean,cooked soybean,soybean sprouts and feed + raw soybean,respectively.Cultured for 30 days.The results showed that different treatments of soybean had no significant effect on the survival and growth of crayfish,but had significant effects on the fatness and hepatopancreas index.The fatness of group E was significantly higher than that of group A and D(P<0.05).The total free amino acids of shrimp meat in group D was the highest,and the total free amino acids in group D and group E were significantly higher than those in the other three groups(P<0.05).The total delicious amino acids in group A and E were significantly higher than those in group B and C(P<0.05).The total amount of sweet amino acids in group E was significantly higher than that in group A,B and C(P<0.05).The ACE index of intestinal flora structure in group A was the highest and significantly higher than that in group C(P<0.05).4.Effects of in vitro incubation on embryonic hatching rate and total bacterial count of crayfish.The experiment was divided into only incubation device(group A),biochemical cotton was placed at the bottom of the incubation device(group B),incubation device + ultraviolet sterilization lamp(group C),and biochemical cotton was added at the bottom of the incubation device + ultraviolet sterilization lamp(group D).20 shrimp eggs were placed in each device,3 in each group.The results showed that different in vitro incubation methods had significant effects on the hatching rate of crayfish embryos.The hatching rate of group D was the highest(80.00%),which was significantly higher than that of group A and group B,and the hatching rate of group C was significantly higher than that of group A(P<0.05).5.Phenotypic traits and transcriptome analysis of sex reversal redclaw crayfish.50 male crayfish(XX group),50 female crayfish(CX group)and 50 sex reversal crayfish(XC group)with body weight of 49.82 ± 11.85 g were selected,and the specific body parameters(full length X1,head and chest length X2,head and chest width X3,total abdominal length X4,first abdominal length X5,first abdominal width X6,metacarpal length X7,body weight Y1,hepatopancreas weight Y2 and gonad weight Y3)were measured,and gonad histological section observation and transcriptome sequencing analysis were performed.The results showed that the parameters of X2/X1,X3/X1,X4/X1,Y2/Y1 and Y3/Y1 of sex reversal shrimp were significantly different from those of female shrimp,and there was no significant difference with male shrimp(P<0.05).The X7/X1 of XX group was significantly higher than that of XC group and CX group,and the XC group was significantly higher than that of CX group(P<0.05).There were a large number of differential genes between female and sex reversal shrimps(7294),including 2528 up-regulated genes and 4766 down-regulated genes.The number of differentially expressed genes between male shrimp and sex reversal shrimp was less,which was 100,including 35up-regulated genes and 65 down-regulated genes.In the comparison of CX and XC,55 differentially expressed genes related to gonad development were screened out,of which 22 were up-regulated and 33 were down-regulated.In the comparison of XX and XC,5 differentially expressed genes related to gonad development were screened out,of which 1 was up-regulated and 4 were down-regulated.RLP24,kinesin heavy chain-like(KHCL),hemicentin-1-like(H1L)and BTF34 genes related to testis degeneration and ovarian development were speculated to be related to sexual reversal. |
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