壬基酚对奥尼罗非鱼(Oreochromis niloticus×O.aureus)的急性毒性研究

NONYLPHENOL:A TOXICANT TO HYBRID TILAPIA (OREOCHROMIS NILOTICUS × O.AUREUS)

采用换水式毒性试验法研究了壬基酚(nonylphenol)对奥尼罗非鱼(Oreochromisniloticus×O.aureus)的急性毒性、遗传毒性效应和对鱼体的器官损伤。结果表明,壬基酚对奥尼罗非鱼的24、48、72和96h的半致死浓度(LC50)分别为413.4、351.5、311.2和264.6μg/L,属剧毒物质。与空白对照相比,奥尼罗非鱼血红细胞的核异常率在最低处理浓度(150.0μg/L)下有显著意义的增加,微核率在≥337.5μg/L时也开始具有显著意义的增加。不同的暴露时间和剂量对血细胞微核率和总核异常率具有不同程度的影响。壬基酚对奥尼罗非鱼的鳃、肾脏、脾、肝均造成不同程度的病理损伤。

Nonylphenol （NP） is a nonionic surfactants, chemically stable and lipophilic, and used globally in the industries of plastics, pesticide and cleanser, widely seen in the effluents. Furthermore, it can be accumulated in aquatic animal body in and transformed to estrogen-like compound. Therefore, it could disturb normal bio-functions of the takers and toxic to them. Groups of 10 randomly collected fish were put in 18L fiberglass tanks and exposed to nominal concentrations of NP at 150.0, 225.0, 337.5, 506.3, and 759.4μg/L separately with ethanol solvent control and water control, for 96h. Test water was renewed once a day to maintain constant NP concentrations and sufficient dissolved oxygen. During the test, poisoning symptoms were observed, and dead individuals were counted and taken out. The LCso and 95% confidence values were calculated according to Kou＇s method （Zhang et al, 1993）. At the end of the exposure test, three fish in each group were collected for analyzing micronucleus and abnormal nuclei, and evaluate histological lesions. Results show that the LC50 of experimental fish exposed for 24, 48, 72, and 96h were 413.4, 351.5, 311.2, and 264.6μg/L, respectively. Therefore, NP is a virulent poison to hybrid tilapia. Abnormal nuclei rates of blood red cells of experimental fish were significantly higher even in the lowest concentration of 150.0μg/L than those in control trials, but the micronucleus rates increased significantly only when the concentration equal to or higher than 337.5μg/L. There were significant pathological changes observed in gill, kidney, spleen and liver after being exposed to NP. It is known that micronucleus occur when a chromosome segment breaks up without centromere left in cytoplasm, or when a chromosome did not move to the pole of spindle. So when fish absorbed NP in test water, NP would disturb karyokinesis of red blood cells and make them aberrated by destroying chromosome or spindle. All the micronucleus to abnormal nuclei rates in NP-exposed groups were higher than control, which suggested that NP is strong inducement effect to fish. The histopathological examination of NP-exposed fish showed significant changes compared to control individuals. NP caused a proliferation of epithelial cell and connection of gill branchial leaflets. These effects blocked the air exchange resulting in oxygen lack. After NP was absorbed in organisms, NP might move to kidney, spleen, and liver by blood circulation, and then degenerate the organs, which consequently disturb bio-function even death. In conclusion, NP is a toxic chemical. Wide usage of NP would cause serious pollution in aquatic environment and inheritable toxicity to fish even to other lives.