摘要：
To determine the toxic effects of waterborne Lead (Pb) on embryonic and larval development of the southern catfish (Silurus meridionalis Chen) ,the embryos and larvae which have been bred with arti-ficial fertilization have been exposed to Pb solutions of five nominal concentrations (0 ,4 ,8 ,12 and 16 mg/L) at 22 .5°C respectively .Embryonic hatching rate ,larval malformation rate ,spontaneous movements , incubation period have been evaluated at the end of embryonic period . Acute toxicity of Pb to newly hatched larvae has also been determined in this study .Embryonic hatchability has decreased with the in-creasing Pb concentration .The value in the groups of 4 ,8 ,12 and 16 mg/L were 71 .23% ,69 .75% ,66 .57%and 64 .69% respectively ,which are significantly lower compared with the control group (84 .94% ) (p<0 .05) .Furthermore ,exposure of embryos to Pb has significantly increased morbidity of body malforma-tions in newly hatched larvae ,such as pericardial edema ,body curvature and degenerated tail .In the groups of 4 ,8 ,12 and 16 mg/L ,the malformation rate of newly larvae are 10 .27% ,15 .28% ,22 .28%and 36 .67% respectively ,which are significantly lower than that of the control group (2 .37% ) (p<0 .05) .The average spontaneous movements of embryos decreased along the contamination gradient .In the concentrations of 4 ,8 ,12 and 16 mg/L ,the value are 63 .86 ,52 .71 ,48 .43 and 47 .14 beats/min , which are significantly lower compared with the control group (78 .00 beats/min) before hatching (44 hours post-fertilization) (p<0 .05) .Pb also has an inhibitory effect on hatching time .The incubation peri-ods are significantly delayed compared to control (p<0 .05) .Exposures to waterborne Pb during embryon-ic period alone causes adverse impact on larval performance even w hen larval development took place in clean w ater .And the lowest larval mortality in 72 hours after hatching occurred in the control group (9 .45% ) , which is significantly lower than that in other groups (18 .22% ,20 .95% ,24 .05% and 26 .29% ) (p<0 .05) . The results in toxic test of Pb to newly hatched larvae show that the median lethal concentration in 96 hours (96h LC50) is 0 .32 mg/L .These results suggest that larvae are more sensitive to Pb toxicity than embryos in southern catfish .Thicker membrane in fertilized egg might have blocking effects to waterborne Pb ,w hich may be one of the most important reason w hy the embryos had higher tolerance to Pb .%采用人工受精获得的南方鲇 Silurus meridionalis Chen胚胎和仔鱼为实验对象，以Pb（NO3）2为毒物源，在水温22.5°C条件下，观察了水体中不同质量浓度铅（Pb）暴露对南方鲇胚胎孵化率、畸形率、自主运动、孵化历时的影响，并进行了初孵仔鱼的Pb暴露毒理实验．实验结果表明，在水体中Pb2＋质量浓度分别为0（对照），4，8，12和16 mg／L的条件下，南方鲇胚胎孵化率随着Pb质量浓度的上升呈下降趋势，分别为84.94％，71.23％，69.75％，66.57％和64.69％，各Pb质量浓度处理组的孵化率显著低于对照组（ p＜0.05）；且孵出的仔鱼出现心包水肿，脊柱弯曲以及尾巴弯曲退化等畸形特征，畸形率随着 Pb质量浓度的升高呈上升趋势，分别为10.27％，15.28％，22.28％和36.67％，各Pb暴露组均显著高于对照组（2.37％）（ p＜0.05）；各Pb质量浓度暴露组胚胎在出膜前期的自主运动频率分别为63.86，52.71，48.43和47.14次／min均显著低于对照组（78.00次／min）（p＜0.05）；各Pb质量浓度暴露组的胚胎孵化历时均显著长于对照组（p＜0.05）．孵化后在净水（未加入Pb（NO3）2的实验水体）中养殖的卵黄囊期仔鱼72 h死亡率随着其胚胎期Pb暴露质量浓度的上升呈上升趋势，胚胎期Pb暴露质量浓度分别为0，4，8，12和16 m g／L的条件下，仔鱼期的净水死亡率分别为9.45％，18.22％，20.95％，24.05％和26.29％，胚胎期各Pb质量浓度暴露组所获仔鱼的死亡率均显著高于对照组（ p＜0.05）．根据水体 Pb暴露对南方鲇初孵仔鱼急性中毒致死的观测结果推算，其96 h半致死质量浓度（96 h LC50）为0.32 mg／L ．本研究结果表明，南方鲇胚胎对水体Pb暴露的耐受性高于其初孵仔鱼，可能与南方鲇的受精卵卵膜较厚，对水体中的Pb2＋进入胚胎具有较大的阻滞作用有关．
