| Recent years, people pay attention to the toxicity of copper, mercury, plumbum,chromium with significant biological toxicity to fish. Heavy metal which can get together in the body through food cycle but not degradation cause chronic poisoring damaging the health of human being. Up to now, there are many reports about damages of low hydrobios of plumbum and chromium, but few repots about plumbum and chromium to Misgurnus anguillicaudatus. Therefor, The experiment used Misgurnus anguillicaudatus as the trier, plumbum and chromium as pollutant, situated in turn again, acute toxicity experience, histologic toxicity test and the inducement of micronuclei and nuclear anomalies. The main findings are as follows:(1) The acute toxicity of plumbum and chromium to Misgurnus anguillicaudatusWe used the methods of single factor toxicity test to detect the acute toxicity effects of plumbum(794.33, 841.40, 891.25, 944.06, 1000.00 mg/L) and chromium(501.19,575.44, 660.69, 758.58, 870.96 mg/L) on Misgurnus anguillicadatus, observed their toxic symptoms, counted the death ratios, educed the regression equations and computed the median lethal concentrations and the safety concentrations under seven concentration grads. The loaches begin to die after 16 hours in plumbum with high concentration( 944.06, 1000.00 mg/L) and after 10 hours in chromium with high concentration( 758.58, 870.96 mg/L). With the increasing concentration and exposure time of two heavy metals, their toxicity effect to Misgurnus anguillicadatus increased. The LC50 of plumbum for 24, 48, 72, 96 hours were 944.06, 909.01, 868.96, 818.46 mg/L, the SC was253.60 mg/L; while the mean LC50 values of chromium for 24, 48, 72, 96 hours were703.07, 676.08, 610.94, 516.42 mg/L, the SC was 187.56 mg/L. Both plumbum and chromium had high toxicity to Misgurnus anguillicadatus, and chromium had higher toxicity than plumbum.(2) The histological damages of gill and liver of plumbum and chromium to Misgurnus anguillicaudatusAccording to the safe concentration and the minimal non-lethal concentration of plumbum and chromium to Misgurnus anguillicaudatus obtained from preliminary tests,four mass concentrations of plumbum(251.19, 371.54, 549.54, 812.83 mg/L), chromium(186.21, 257.04, 354.81, 489.78 mg/L) were set up, gill and liver of M.anguillicaudatus at 7, 14, 21, 28 d were observed using H·E method. The gill exposed to 812.83 mg/L plumbum become enlarged and curled the distal of branchial, and necrotizing exfoliated gill cells at 14 d but after 7 d in chromium with concentration(489.78 mg/L). The hepatic cells exposed to 812.83 mg/L plumbum become bubbled, and experienced lysis and nucleus deformation,and additional karyolysis was observed after 7 d. The hepatic cells exposed to 354.81 mg/L chromium for 14 d were enlarged and bubbled, and cell lysis was observed, while karyolysis and nucleus deformation were observed in addition to swelling, vacuolization and lysis on that exposed to 489.78 mg/L chromium for 14 d.Plumbum and chromium damaged liver structure of Misgurnus anguillicaudatus and the damages aggravated as the increase of exposure concentrations.(3) The inducement of micronuclei and nuclear anomalies of plumbum and chromium to Misgurnus anguillicaudatusGenetic toxicity of plumbum and chromium on erythrocytes nucleus of Misgurnus anguillicaudatus was studied by using micronuclei and nuclear anomalies tests. In this study, four plumbum levers, i.e. 251.19, 371.54, 549.54, 812.83 mg/L, chromium levers186.21, 257.04, 354.81, 489.78 mg/L were chosen for gradiend. The peripheral red blood cells of M. anguillicaudatus were sampled on 3, 6, 9, 12 d respectively. The results showed that, there were more micronuclei and some kinds of nuclear anomalies after exposure in plumbum and chromium than control groups, including two-nuclei, nucleus endo-vacuole, Cytoplasm protrude, enucleated cell, karyopyknnosis, nucleus evagination,concave nucleus, anomalous nucleus position, nucleus chromatin grains and so on. Thefrequencies of micronuclei and nuclear anomalies in M. anguillicaudatus exposing to relatively lower levers of plumbum(251.19, 371.54 mg/L), chromium(186.21, 257.04mg/L)increased with the increasing of exposure concentrations and duration. However,under the higher levers of plumbum(549.54, 812.83 mg/L), chromium(354.81,489.78mg/L)stresses, the frequencies of micronuclei and nuclear anomalies increased and then decreased with the increasing of exposure concentrations and duration. In addition, the frequencies of micronuclei in M. Anguillicaudantus exposing to plumbum and chromium were lower than of nuclear anomalies. Our results indicated that plumbum and chromium had a potential genetic toxicity on M. anguillicaudatus. The genotoxic effects of plumbum and chromium increased with the increasing lever of exposure concentrations or duration under certain exposure condition. However, the genotoxic effects would be inhibited depended on the exposure duration and plumbum and chromium levers. As to the lower frequencies of micronuclei than that of nuclear anomalies, which might related to the loe mitotic index of the peripheral blood erythrocytes and different plumbum and chromium induced mechanisms between micronuclei and nuclear anomalies on M.anguillicaudatus. |
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