| There are many problems in the breeding of Procambarus clarkii.For example,iron-shell shrimp were produced under high-density culture,and the fishing and breeding of the seedlings led to stress.Dry dew stress occurred during dry transportation,accompanied by changes in body color,which was speculated to have a certain relationship with density and dry dew.In the process of indoor culture,it was found that the body color of Procambarus clarkii cultured in small size for a long time would partly turn blue,and astaxanthin could not be produced in the body of Procambarus Clarkii,so it could only be supplemented from the outside world.Some studies have shown that the addition of astaxanthin in feed can significantly improve the body color of crustaceans,which is presumed to be related to astaxanthin to some extent.Therefore,this paper studied the effects of density,dry dew stress and exogenous astaxanthin deficiency on the body color of Procambarus clarkii,as well as the relationship between the changes of pigment cells and pigment content.In order to provide some reference value for practical breeding experience.1.Effect of density stress on body color of Procambarus clarkiiThe aim of this experiment was to investigate the effects of different densities on the contents of lactate(LD),glucose(GLU),cortisol,total superoxide dismutase(T-SOD),malondialdehyde(MDA)in hepatopancreas and astaxanthin in cephalopastriae of Procambarus clarkii.Three density groups were set up in this experiment,which were300 animals/m~2,150 animals/m~2 and 50 animals/m~2 respectively.Samples were collected and pigment cells were observed at 0,2,4,8,12,24 and 48 h.The results showed that the change of redness(a*)value was the most obvious in the 300 female and male shrimp/m~2 group,and the change of redness value showed an increasing trend with the density,but a*value decreased at 12 h,and a*value reached the maximum at 48 h for both female and male shrimp.The morphology of red pigment cells changed before and after stress,and they were spot-like before stress.After stress,the diameter of red pigment cells gradually increased and overlated with each other.Yellow pigment cells,blue pigment cells and melanocytes had no obvious changes.The contents of glucose and cortisol in serum increased with the increase of density and time.The content of T-SOD in hepatopancreas decreased except for 50/m~2,and MDA content in all treatment groups was higher than that in non-stress group at all time points.Astaxanthin content in 300animals/m~2 treatment group was lower than that in control group.In conclusion,density stress can change the body color of Procambarus clarkii.The higher the density,the faster the body color turns red,and the faster the pigment cells change from spot to dendritic.2.Effect of density stress restoration on body color of Procambarus clarkiiIn order to study whether the body color would recover at the same time of monoculture recovery after density stress,the monoculture recovery in water after density stress of 300 animals/m~2,150 animals/m~2 and 50 animals/m~2 were set as HT300 group,HT150 group and HT50 group.Groups of 300 birds/m~2,150 birds/m~2 and 50 birds/m~2were recorded as HG300 group,HG150 group and HG50 group after recovering for 12 h after stress.The density recovery experiment shows that group HT300,group HT150 and group HT50 can all recover color,and the recovery time is lengthened with the increase of density,but they can all recover after 12 h under the condition of this study.After 12 h monoculture recovery in groups HG300,HG150 and HG50,the body color of Procambarus clarkii recovered and the red pigment cells in the side of the sternae recovered to be punctate.The contents of lactic acid,glucose and cortisol in serum did not return to the initial level.In conclusion,after short-term density stress and mono-culture,the body color could be restored within 12 h,and the red pigment cells in the side of the sternoplax subsequently returned to dot shape,but the stress index did not return to the initial level.3.Effect of dry dew stress on body color of Procambarus clarkiiTo study the effect of dry dew on the body color of juvenile Procambarus clarkii(5±0.8 g),four groups were set up:air humidity(48±5%,group A),(85±5%,group B),air humidity(48±5%,water level 0.2 cm,group C)and control group.And seven drying time(0.5 h,1h,2 h,4 h,8 h,12 h and 24 h)were set in each group.The results showed that the survival rates of male and female shrimps in groups A,B and C were 100%after 12 h of dry dew stress.After 24 h dry dew stress,all the patients in group A died,the survival rate in group B decreased,and all the patients in group C survived.With the extension of dry dew stress time,the a*value of individual body color in groups a,B and C increased gradually.The blood glucose concentration showed a trend of first increase and then decrease,and the serum lactic acid content showed a trend of first increase and then decrease.The damage of hepatopancreas and branchial tissue structure was gradually intensified with the extension of dry exposure time,and the damage degree of group C was lower than that of group A and B.The body color of the individuals under dry dew stress was restored to the original body color after 12 h monoculture in water.The morphology of red pigment cells in the side of the sternoplax was restored to point shape.The damage of hepatopancreas and branchial tissue recovered somewhat but not completely,and the recovery degree of hepatopancreas was better than branchial tissue.In conclusion,dry dew stress can cause the body color of Procambarus clarkii to turn red,and the red pigment cells change from spot-like to dendritic with the change of body color,and their diameters gradually increase.4.Effects of astaxanthin deficiency on body color,physiology and biochemistry of Procambarus clarkii with different body colorIn this study,two kinds of isonitrogenous and lipid-equal diets were prepared,which were supplemented with 0.9%Rhodococcus immaculata meal and the non-added group,respectively.The offspring of red shell shrimp and blue shell shrimp were fed with the non-added group diet(RC group,BC group),and supplemented with 0.9%Rhodococcus immaculata meal(RT group,BT group),respectively,for 60 days.The results showed that the survival rate of RT group was 100%,which was significantly higher than that of RC group,and the activities of antioxidant enzymes and digestive enzymes in RT and BT groups were higher than those in RC and BC groups.In hepatopancreas,muscle and cephaloperax,the pigment contents in RT group and BT group were significantly higher than those in RC group and BC group.The brightness(L*)values of the side and top of the sternplate and the whole shrimp in RC and BC groups were significantly higher than those in RT and BT groups.The a*value in the side,top and whole prawns addition groups was significantly higher in RT and BT groups than in RC and BC groups.In RC group and BC group,the color of red pigment cells became light and the body color became blue.The color of red pigment cells in RT group and BT group was darker and the body color was normal.Hepatopancreas were improved in addition group,but no changes were observed in intestinal tract.In conclusion,astaxanthin deficiency can lead to blue body color and light red pigment cell color of shrimp,and the normal body color can be restored and the survival rate and antioxidant capacity can be improved by feeding astaxanthin. |
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