| The present study was conducted to evaluate the toxic effect of water-borne lead (Pb) on the juvenile Spinibarbus sinensis. The artificial compound soft water (25mg CaCO3/L) were used in the following two series of experiment at constant temperature (27.5℃):1. According to the preparatory experiment, we set up different concentrations groups of Pb in acute exposure experiment, with0,12.5,14.0,15.5,17.0,18.5,20.0mg Pb/L, respectively. The growth performance of S. sinensis (weight range8.52±0.24g) were observed, and showed that as the concentration of Pb rising, the mortality rates of S. sinensis increased. Using the linear interpolation method, we got the LC50of the S. sinensis was at96h with15.75mg Pb/L.2. Based on the96h LC50measured in acute exposure experiment, the concentrations of Pb in chronic exposure experiment were set at Omg Pb/L (control group),0.1mg Pb/L (low concentration group) and0.5mg Pb/L (high concentration group). After10weeks’satiate feeding on artificial formulated diet, we tested the growth performance, the energy allocation and the blood indexes of S. sinensis, the effect of waterborne Pb exposed on the growth performance and energy distribution mode of S. sinensis (initial weight38.88±0.95g) were approached.The main results are as follows:①During the10-week chronic exposure experiment, the final weight of the fish decreased with the increasing concentration of Pb. The values in Pb treatment group were higher than that in the control group (P<0.05). But there was no significant difference between the high and low Pb concentration groups. The condition factor, growth rate of specific weight, feed efficiency, protein efficiency, protein and energy accumulation rates all decreased with the increasing concentration of Pb, and values in high concentration group were significantly lower than that in the control group (P<0.05). The feeding rates of dry matter, protein and energy increased with the increasing concentration of Pb, and the high concentration group was significantly higher than that in the control group (P<0.05). The apparent digestibility of S. sinensis increased with the increasing concentration of Pb, but there was no significant difference among three groups.②The crude protein content of S. sinensis showed a decline trend with increasing Pb concentration, but there was no significant difference among all group. Moisture and ash content of fish increased with increasing Pb concentration, and the high concentration group was significantly higher than that of control group (P＜0.05). However, the content of crude fat and energy density decreased with the increasing concentration of Pb, and the value in the high concentration group was significantly lower than that in the control group (P＜0.05).③Standard weight metabolic rate of S. sinensis decreased with the increasing concentration of Pb. And the value in the high concentration group was significantly lower than that in other two groups (P<0.05). But there were no significant difference in the SDA coefficient, SDA energy consumption, and feeding metabolism peak/standard metabolism among all groups. SDA peak in the high concentration group was significantly lower than that in other two groups (P<0.05).④Blood glucose of S. sinensis increased with the increasing concentration of Pb. And the value in the high concentration group was significantly higher compared with that in control group (P＜0.05). The content of total protein in serum, glycogen content both in hepatopancreas and muscle showed a declined trend with the increasing concentration of Pb and there was no significant difference among different concentrations. Triglyceride in serum showed a significant lower than that of control group. ⑤Serum alanine aminotransferase (ALT) activity increased with the increasing concentration of Pb in water. Two Pb treatment groups were significantly higher than that of control group (P<0.05). Serum aspertate aminotransferase (AST) also increased with Pb with the increasing concentration of Pb, and differences among each group were significant (P<0.05). However, both ALT activity and AST activity in hepatopancreas decreased with the increasing concentration of Pb, and differences among each group were significant (P<0.05).⑥There was no significant difference for the ingested nitrogen, defecated nitrogen, growth nitrogen and the discharged nitrogen among each group. The proportion of nitrogen budget in each component was calculated as the ingestion nitrogen as100%. The results showed that the percentage of growth nitrogen decreased with the increasing concentration of Pb, and the value in the high concentration group was significantly lower compared with that in the control group (P＜0.05), but neither the value in the high concentration group nor that in the cntrol group was significantly different with that in the low concentration group. There was no significant difference among different Pb concentrations groups in the percentage of defecated nitrogen. The percentage of discharged nitrogen increased with the increasing concentration of Pb in water, which the high concentration group was significantly higher than that of cntrol group (P＜0.05), but there was no significant difference between the low concentration group and other two groups.⑦There was no significant difference for the ingestion and growth energy among the three concentration groups. Standard metabolic energy decreased along with the increasing concentration of Pb, and that in the higher concentration group was significantly lower compared with the control group and the low group (P＜0.05). However, there was no significant difference among each group in specific dynamic action, activity metabolism energy and defecated energy. The defecated energy increased with the increasing concentration of Pb, with the high group significantly higher than that of control group (P<0.05), but neither the value in the high concentration group nor that in the cntrol group was significantly different with that in the low concentration group. Conclusions:①Comparing with the data reported in literatures, the96h LC50of Pb to S. sinensis maintained at a higher level, indicating that S. sinensis has low tolerance to the Pb toxicity.②In chronic exposure experiment, activitives of ALT and AST in serum increased with the increasing concentration of Pb but declined in liver, which suggested the liver of S. sinensis have been damaged. It might be the reason that caused S. sinensis suppression in metabolic rate.③With chronic exposure, food intake level of S. sinensis increased with the increasing concentration of Pb, at the same time, the food utilization efficiency reduced, which caused the decrease in food assimilation efficiency. Therefore, the growth of S. sinensis was inhibited.④Energy distribution pattern of S. sinensis changed with Pb exposure:the proportion of discharged energy increased and the proportion of food energy which was used for growth declined. Thereby, energy assimilation efficiency reduced, and the metabolism energy proportion in assimilation energy increased, resulted in the reduced proportion of growth energy in assimilation energy. |
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