| In the present study, To determine the toxic ecotoxicological of waterborne Lead (Pb) on early life stages (ELS:embryos, and larvae) of the southern catfish (Silurus meridionalis) which were bred using artificial fertilization were exposed to Pb solutions of different concentration at 22.5 ℃. Two series of experiments were carried out in this study:The main results are as follows:Ⅰ. 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 were exposed to Pb solutions of five nominal concentration (0,4,8,12 and 16 mg/L) respectively. Acute toxicity of Pb to newly hatched larvae was also determined in this study.Ⅱ. The embryonic period (larval stage) is exposed by heavy metals, which were divided into four treatment groups, Control (0-0), Recovery (Pb-0), Semi-continued (0-Pb), Continued (Pb-Pb). The concentration of Pb were set at 50,100,200,400 μg/L in last three groups.The results in the first experiment were shown as follows:1. Embryonic hatchability decreased with the increasing concentration of Pb rising. Furthermore, exposure of embryos to Pb significantly increased morbidity of body malformations in newly hatched larvae. Pb also had an inhibitory effect on hatching time, which were significantly delayed.2. The newly hatched larvae mortality were increases with the concentration of Pb rising. We got the LC50 of the newly hatched larvae of southern catfish is 320 μg/L at 96h.The results in the second experiment were shown as follows:1. The final weight of the fish deceased with the increasing concentration of Pb rising. The fishes final weight of clear water groups only the level of the highest does (400-0 μg/L) were significantly lower than the control group (P<0.05). When the concentration of Pb is more than 50 μg/L in the groups of Semi-continued and Continued, the final weight of fish were significantly lower than the control group (P<0.05). The final weight of the fishes that were exposure or not exposed to heavy metals during embryonic period from weight was no obvious difference between this groups (P<0.05).2. The standard weight resting metabolic rate of southern catfish increased with the concentration of Pb rising. The standard weight resting metabolic rate of recovery groups only the level of the highest does (400-0 μg/L) were significantly higher than the control group (P<0.05). The standard weight resting metabolic rate of Continuous groups between with Semi-continuous groups was no significant different.3. The glycogen contents of liver decreased with the concentration of Pb rising. The glycogen contents of liver in recovery groups only the level of the highest does (400-0 μg/L) were significantly lower than the control group (P<0.05). When the concentration of Pb are more than 100 μg/L, the glycogen contents of liver were significantly lower during Continuous groups and Semi-continuous groups. But glycogen contents of muscle was no significant different among this treatment groups.4. The activities of T-AOC, SOD and CAT in gill, liver and kidney were induced with the concentration of Pb increasing during the recovery groups. The activities of T-AOC, SOD and CAT in gill, liver and kidney of recovery groups only the level of the highest does (400-0 μg/L) was significantly higher than the control group (P<0.05). The activities of T-AOC, SOD and CAT in gill, liver and kidney of Continuous groups and Semi-continuous groups were significantly lower. However, it’s no significant difference in activity of these enzymes between the two treatment groups.5. The GSH contents of gill, liver and kidney decreased with the concentration of Pb rising. The GSH contents of Continuous groups and Semi-continuous groups were was significantly lower than the control groups. The GSH contents of Continuous groups between with Semi-continuous groups was no significant different in the same concentration of Pb.6. The MDA contents of gill, liver and kidney increased with the concentration of Pb rising. The MDA contents of recovery groups only the level of the highest does (400-0 μg/L) were significantly higher than the control group (P<0.05). The MDA contents of Continuous groups and Semi-continuous groups were was significantly higher than the control groups. It was no significant different the MDA contents of Continuous groups between with Semi-continuous groups in the same concentration of Pb.7. The activities of TChE were lower with the concentration of Pb rising in the brain of fishes. When the concentrations of Pb are more than 200μg/L, The activities of TChE were significantly lower than control groups.8. The contents of lead in gill, liver, kidney, gut, stomach, muscle and whole fish increased with the concentration of Pb rising, and the contents of lead in gill, liver and kidney were more than other tissues. The lowest lead contents is muscle in all tissues. The Pb contents of same tissues of Continuous groups between with Semi-continuous groups was no significant different in the same concentration of Pb.The conclusions suggested in this study were as follows:1. Embryonic hatchability decreased with the increasing Pb concentration. Furthermore, exposure of embryos to Pb significantly increased morbidity of body malformations in newly hatched larvae. Pb also had an inhibitory effect on hatching time. The incubation periods were significantly delayed. The newly hatched larvae are in the process of early development of Pb exposure to the most sensitive period. Thicker membrane in fertilized egg might have blocking effects to waterborne Pb, which may be one of the most important reason why the embryos had higher tolerance to Pb.2. The standard weight resting metabolic rate of southern catfish increased with increasing lead exposure concentration. Pb exposure to water will inhibit the growth of fish, and improve the resting metabolic rate of southern catfish, reduced glycogen content of liver, but there was no significant effect on glycogen of muscle. The glycogen contents of liver in recovery groups only the level of the highest does (400-0 μg/L) were significantly lower than the control group, indicating the toxicological effects of lead exposure on embryos will lag effect in the larval growth and metabolism. The marker of increased with the concentration of Pb rising in Continuous groups and Semi-continuous groups. The marker of Continuous groups between with Semi-continuous groups was no significant different in the same concentration of Pb.3. The active reaction of AChE in brain of southern catfish is very sensitive to exposure to Pb, it may be used as a biochemical criterion to show the degree of heavy metal poisoning of the brain indirectly.4. The activities of T-AOC, SOD and CAT in gill, liver and kidney were induced with the concentration of Pb increasing during the recovery groups, showed the antioxidant of the tissues will adjust itself to cope with the stress of toxicity caused by exposure to Pb. The activities of T-AOC, SOD and CAT in gill, liver and kidney of Continuous groups and Semi-continuous groups were significantly lower. When expose of Pb were happened, the antioxidant system of gills, liver and kidney were activated quickly to deal with the stress of ROS caused by exposure to heavy metals.5. The contents of lead in gill, liver, kidney, gut, stomach, muscle and whole fish increased with increasing Pb concentration, and the contents of lead in gill, liver and kidney were more than other tissues. The lead contents of muscle are the lowest in all of tissues. The fishes were exposure in the embryonic, after restoring growth, the fishes still accumulated a certain amount of lead, indicating accumulation of heavy metals difficult to remove. The Pb contents of same tissues of Continuous groups between with Semi-continuous groups was no significant different in the same concentration of Pb, supporting the egg membrane blocks the Pb move into the body point of view. |
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