Studies On Stress Resistance Of Different Ploidy Crucians Under Cadmium Stress

With the rapid development of industrialization,environmental pollution is increasingly serious.Among them,the pollution of heavy metal cadmium was especially prominent.As a kind of common aquatic organisms,crucian carp could absorb and accumulate heavy metals from water and enriched in hepatopancreas,kidney,gill,fin and other parts.A series of factors,such as exposure time,exposure concentration,environmental temperature,etc.,could affect the accumulation of carassius auratus.Triploid crucian carp(3n=150),a high quality new variety developed by the State Key Laboratory of Developmental Biology of Freshwater Fish,which has high adverse resistance and strong adaptability to harsh natural environment,mainly in low temperature resistance and disease resistance.Therefore,diploid red crucian carp(2n=100)and triploid crucian carp were used as materials to study the resistance of difierent ploidy crucian carp under cadmium stress in embryo,larvae and adult fish periods.The main findings were as follows:1.Acute toxicological experiments on different ploidy crucian carp embryo under cadmium stressDifferent ploidy crucian carp embryos were treated by Cd2+ gradient solution prepared separately from 3CdSO4·8H2O and CdCl2·2.5H2O in the acute toxicity test of embryos.The mortality rate of the embryos within 96 h was counted.No significant difference was found in the mortality rate of different ploidy crucian carp embryos,and mortality rate was lower when the concentration of these two different of Cd2+solution was 0?9 mg/L or 0?3 mg/L,separately.While high mortality rate of embryos,even all dead,when Cd2+ concentration added to 12 mg/L or 4 mg/L.The toxicity of CdCl2·2.5H2O to different ploidy crucian carp embryos was higher than that of 3CdSO4·8H2O.The cadmium content of embryo and egg membrane in the treated and control groups was determined by atomic absorption spectrophotometry,the cadmium content of egg membrane was far higher than that of embryo from diploid red crucian carp and triploid crucian carp in treated groups,even more than 11 times.In control groups,the cadmium content of egg membrane was 56 times higher than that of embryo in diploid red crucian carp,and 45 times higher in triploid crucian carp.After treated by 9 mg/L Cd2+solution,the cadmium content of egg membrane was far higher than that of embryo,324 times in diploid red crucian carp and 536 times in triploid crucian carp.Egg membrane could block effectively embryo from absorbing cadmium and to protect embryo.The abnormality rate of different ploidy crucian carp larvae was increased under cadmium stress.The deformity mainly manifested pericardial cavity edema,tail/spinal cord bend,yolk sac digestive abnormally,tail loss,melanin reduce and eye dysplasia.2.Acute toxicological experiments on different ploidy crucian carp larvae under cadmium stressIn the acute toxicity test,the mortality rate of different ploidy crucian carp larvae under cadmium stress within 96 h was counted.It was foirnd that the mortality rate of different ploidy crucian carp larvae correlated positively with exposure time under cadmium stress.The toxicity of cadmium to triploid crucian carp larvae was higher than to diploid red crucian carp larvae in 3?6 mg/L cadmium concentration.When cadmium concentration was 9 mg/L,the mortality rate at 96 h of diploid red crucian caip larvae was 94%and that of triploid crucian carp larvae was just 51.9%.Triploid crucian carp had stronger cadmium tolerance.The cadmium content of larvae was determined by atomic absorption spectrophotometry,cadmium content of diploid red crucian carp larvae increased with cadmium concentration increasing.Cadmium content of trip lo id crucian carp larvae treated by 3 mg/L Cd2+was very high,while decreased at 6?9 mg/L Cd2+solution,decreased first and then increased.3.Acute toxicological experiments on different ploidy crucian carp adult fish under cadmium stressCadmium exposure time,cadmium exposure concentration and organism development degree were confirmed to affect survival rate of different ploidy crucian carp.The mortality rate of small diploid red cruchan carp was 83.3%under 9 mg/L cadmium solution stress in 96 h,while the same size of triploid crucian carp were all alive.The mortality rate of small dip bid red crucian carp was 100%under 15 mg/L cadmium solution stress at 24 h,while the mortality rate of same size of trmloid crucian carp was 66.7%in 96 h.The cadmium content of larvae was determined by atomic absorption spectrophotometry and showed that there were differences in enrichment ability of cadmium among different tissues of crucian carp adult fish.The cadmium content was highest in kidney and hepatopancreas,lower in muscle and skin.The cadmium content in kidney or hepatopancreas of diploid red crucian carp was higher than of triploid crucian carp.Cadmium stress caused marked histological injury to both hepatopancreas and kidney of ploidy crucian carp dult fish.Hepatic cords disorder,ballooning degeneration,fatty degeneration were found in hepatopancreas,while kidney damage represented epithelial cellular swelling and coagulation necnosis of kidney.4.The expressions analyses of PP2A and HSP in tissue of different ploidy crucian carp under cadmium stressThe expression of PP2A-B,,y,PP2A-B,5a,PP2A-PR/B[R,HSP30,HSP40,HSP70 and HSP90 in hepatopancreas and kidney from control group and treated group were detected by RT-PCR.The expression of PP2A-B"a in hepatopancreas and kidney was significantly increased in both different ploidy crucian carps under cadmium stress,particularly in diploid red crucian carp.The expression of HSP30 and HSP70 in diploid red crucian carp and hepatopancreas of triploid crucian carp was also significantly increased.In conclusion,the response of diploid red crucian carp and triploid crucian carp to cadmium stress was studied,and the results showed that triploid crucian carp adult fish had stronger cadmium resistance than that diploid red crucian carp,which provided some ideas and basis for further study on molecular mechanisms of cadmium resistance and other environmental resistance in trip loid crucian carp.