| The effects of the cadmium exposure on the reproductive capacity and offspring development of zebrafish were studied by using semi-static toxic test method.According to 96 h LC50 values and the National Fisheries Standards of China,we set five Cd treatment groups(0.058 mg·L-1,0.116 mg·L-1,0.232 mg·L-1,0.580 mg·L-1,1.160 mg·L-1)and one control group without Cd.Firstly,after cadium exposure for 21 d,mating success rate,fecundity,fertilization rate of female zebrafish and survival rate,hatching rate,heart rate,deformity rate,body length indexes of their offspring were studied by statistical analysis to explore the effect of low concentrations of cadmium on the reproductive capacity and offspring development of zebrafish.Secondly,on the basis of this experiment,we examined the activities of antioxidant enzymes and the level of lipid peroxidation in ovaries,analysised changes of the ovary and oocyte,revealed the effects of low concentrations of cadmium on the oxidative damage of zebrafish ovary and the changes of its structure.At last,we further assessed the antioxidant enzymes related genes expression level of sod?cat?gpx and the reproductive gene expression level of dazl?vasa?nanos1 by rael time PCR to explore the effect of cadmium on the molecular level of ovary.The results showed that:1.Effects of low concentration cadmium exposure on the reproductive capacity and offspring development of zebrafish The mating success rate,production,fertilization rate of female zebrafish decreased after cadmium exposure,even in the high concentration group 1.160 mg·L-1 were sterile;These indexes of their offspring embryos such as survival rate,hatching rate,heart rate,malformation rate,body length compared with the control group,were significantly changed with a concentration-dependent manner;Embryos development appeared several deformity morphology included melanin growth retardation,pericardial and yolk sac edema,bladder developmental abnormalities.2.Effects of cadmium exposure on ovarian tissue and cell of mature female zebrafishMicroscopic observation showed that cadmium exposure caused severe damage to ovarian tissue,oocyte membrane folding,cell shrinkage and oocyte atresia.Compared with those in the control group,the activities of antioxidant enzymes SOD,CAT and GPx were decreased significantly and the content of MDA was increased significantly in each Cd-treated group with a concentration-dependent manner.3.Effects of cadmium exposure on the molecular level of ovarian tissue in mature female zebrafish The results showed that: the expression of sod gene in each concentration group were significantly decreased compared with the control group,and the expression of sod gene in 1.160 mg·L-1 also appeared significant difference compared to other cadmium concentrations.Compared with the control group,the expression of cat gene appeared a trend of increased firstly and then decreased secondly and above all concentration groups existed a significance differences.The expression of gpx gene were decreased compared with the control group,there was a significant difference in middle and high concentration groups.Compared with the control group,the expression of dazl gene in the Cd treatment group was significantly lower than that in the control group,and there was a significant difference in the 0.058 mg·L-1 concentration group.The expression of vasa gene was decreased compared with the control group,in the low concentration group(0.058 mg·L-1,0.116 mg·L-1)had no significant changed,in the high concentration group(0.232 mg·L-1,0.580 mg·L-1,1.160 mg·L-1)showed a significant difference.The expression of nanos1 gene compared with the control group showed a trend of decrease,in the low concentration group 0.058 mg·L-1 had no significant difference,but there was a significant difference in the middle concentration group,the high concentration group(1.160 mg·L-1)had a significant difference compared with other cadmium concentration group.Conclusions:(1)Low concentration of cadmium exposure decreased zebrafish reproductive ability,and the reproductive toxicity through maternal transfered to their offspring,thus influenced the growth and development of offspring.(2)Cadmium exposure decreased the antioxidant enzymes in zebrafish ovary and resulted in the changes in the morphology of ovarian tissue and cells,eventually leaded to the decrease of reproductive capacity.(3)Related gene expression of antioxidant enzyme and reproductive all decreased significantly after cadmium exposured.This indicated that cadmium had effects on the molecular level of antioxidant enzymes and reproduction in zebrafish and inhibited the development of the ovary,reduced reproductive capacity.These changes in gene expression whether through maternal transfer to offspring and affect their offsprings survival and development remain to be further studied. |
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