Lanthanum Induces Acute And Subchronic Toxicity And Its Physiological And Genetic Effects In Gobiocypris Rarus

Gobiocypris rarus,an endemic species of China,is one of the recommended test organisms in the Guidelines for the testing of chemicals.Through performing tests of semi-static biological acute toxicity,effects of lanthanum inducing acute toxicity on G.rarus were researched to assess its ecological environment toxicology.An embryo-yolk sac stage larva toxicity test was conducted to investigate the effects of lanthanum on fish early life stages.In 21d chronic toxicity test,the effects of lanthanum on the antioxidase activity and MDA content,histopathological changes in gill and liver tissue and its genotoxicity in G.rarus were observed.The results were shown as follows:1.The median lethal concentration(96 h:LC₅₀)of La³⁺was 1.92 mg/L and its95%confidence interval was from 1.74 to 2.14 mg/L.The safe concentration?SC?value of La³⁺was 0.19 mg/L.The no observed effect concentration?NOEC?,lowest observed effect concentration?LOEC?and maximum acceptable toxicant concentration?MATC?was 1.58,2.51 and 1.99 mg/L,respectively.The evaluation of the toxicity of lanthanum exposure to fish was Acute II?highly toxic?.2.High concentration of La³⁺?1.92,1.00 mg/L?had obvious lethal effects on embryo which died at 38h and 60h,respectively.The frequency of spontaneous movement of embryo exposed to La³⁺was lower/significant lower than that of the control group?P<0.01?.The heart rate of embryo exposed to low concentration level of La³⁺?0.06 mg/L?was increased?P>0.05?,but decreased or decreased significantly while exposed to high concentration level of La³⁺?0.25,0.50 mg/L?.What's more,La³⁺exposure has a significant inhibitory effect on the hatching rate of exposed 96h.With the extension of exposure time,the larvae appeared obvious pericardium edema,yolk-sac edema,spinal curvature,tail bending and other symptoms of poisoning,including unformed function swim-bladder.Compared with control group,the pericardium and yolk-sac edema areas of larvae exposed to 0.13 and 0.06 mg/L La³⁺were significantly higher?P<0.01?,while significantly decrease about body length were observed?P<0.05?.3.The activity of superoxide dismutase?SOD?in hepatopancreas of fish exposed to lower La³⁺concentration?0.04⁰.32 mg/L?was lower than that of the control group?P>0.05?,otherwise it was increased in that of fish exposed to 0.80 mg/L?P>0.05?.There was no significant difference about the activity of Catalase?CAT?between groups exposed to La³⁺and the control group;moreover,it showed a similar trend with the activity of superoxide dismutase?SOD?.Malondialdehyde?MDA?contents in hepatopancreas of fish exposed to0.04⁰.16 mg/L increased?P>0.05?;however,it was higher/significant higher in group of 0.32/0.80 mg/L.Malondialdehyde contents in hepatopancreas of fish exposed to 0.80 mg/L was also significant higher than that of group exposed 0.04⁰.32 mg/L.4.The main histopathological changes observed in gills were epithelial lifting,filamentary epithelial proliferation and edema,lamellar fusion,desquamation and necrosis.Liver showed dilation of sinusoids,focal congestion,pyknotic nucleus,karyohexis and karyolysis,vacuolar degeneration,focal and numerous necrosis areas.Compared with the control group,hypsometric analysis documented significant differences in measurements of gill dimensions?average length,width,area?,suggesting metabolic disturbance?gas exchange?upon La³⁺exposure.The result showed that La³⁺toxicity severely affecting gill and liver.5.After exposed to La³⁺for 21d,individuals were collected to prepare blood smear by cutting off the tail.Frequency of micronucleus,nuclear anomalies and size of erythrocytes were determined to estimate its genotoxicity effects on G.rarus.Compared with the control group,rates of micronucleus of fish in each La³⁺exposure group tend to increase?P>0.05?;rates of nuclear anomalies and total nuclear anomalies of fish exposure to concentration of La³⁺?0.08⁰.80 mg/L?were significantly increased?P<0.05?;diameter of cell and nucleus tend to decrease or significantly decrease?P<0.05?.Our results suggested that lanthanum is highly toxic substance according to acute toxicity grading standard.High genotoxicity may be observed in aquatic animals exposed to rare earth elements for a long period.