环境相关浓度五氯苯酚全生命周期暴露对大型溞的毒性效应研究

Whole-Life-Stage Toxic Effects of Pentachlorophenol in Daphnia magna at Environmentally Relevant Concentrations

水环境是众多化学污染物的归宿地,因此水生生物,尤其是生命周期短的浮游动物,可能在整个生命阶段均处于污染物的暴露中并受到相应的环境危害。五氯苯酚(pentachlorophenol,PCP)是一种典型的持久性有机污染物,其在自然水体中的浓度从几ng·L^(-1)至几十μg·L^(-1)不等。已有的毒理学研究探究了PCP对水生生物部分生命阶段的慢性毒性效应,而对其全生命周期的环境危害鲜有报道。因此,本研究以浮游模式动物——大型溞(Daphnia magna)为受试生物,探究了环境相关浓度PCP全生命周期暴露对其存活、生长、生殖、心率、游泳行为和基因表达的影响。环境相关浓度(1.74±0.05)、(16.84±1.13)和(166.11±9.47)μg·L^(-1) PCP暴露显著抑制了大型溞的游泳行为、心率、个体生长和生殖,引起了大型溞群体的过早死亡。基因转录结果显示PCP暴露显著上调了大型溞生命晚期与心脏疾病和神经递质相关途径的基因表达,表明大型溞在生命晚期阶段存活率的下降可能与心脏功能障碍和神经活动抑制有关。此外,本研究发现随着暴露时间的延长,大型溞各毒性指标的最低观察有效应浓度(lowest observed effect concentration,LOEC)呈下降趋势,表明污染物全生命周期暴露对大型溞具有更大的环境危害。综上所述,本研究结果表明化学品部分生命周期的暴露实验可能低估了环境污染物的环境危害,因此将来开展浮游动物的全生命周期暴露实验评估化学品的环境危害是有必要的。

The water environment is the destination of many chemical pollutants,so aquatic organisms,especially zooplanktons with short life span,may be exposed to pollutants and suffer related environmental hazards in the whole life stage.Pentachlorophenol(PCP)is a typical persistent organic pollutant.The concentrations of PCP in natural water ranged from a few ng·L^(-1) to dozens ofμg·L^(-1).Previous toxicological studies have evaluated the chronic toxic effects of PCP in partial life stage of aquatic organisms,but the environmental hazards to its whole life stage have been rarely reported.Therefore,in this study,the zooplankton model animal,Daphnia magna(D.magna),was used to evaluate the effects of PCP exposure at environmentally relevant concentrations on its survival,growth,reproduction,heart rate,swimming behavior and gene expression.Exposure of PCP at environmentally relevant concentrations(1.74±0.05),(16.84±1.13)and(166.11±9.47)μg·L^(-1) significantly inhibited swimming behavior,heart rate,individual growth and reproduction of D.magna,resulting in premature death of D.magna.The results of gene transcription showed that PCP exposure significantly up-regulated the expression of genes included in pathways related to heart disease and neurotransmitters during the stage of death,indicating that the decrease of survival rate of D.magna during the stage of death might be related to cardiac dysfunction and inhibition of neural activity.In addition,this study found that with the extension of exposure time,the lowest observed effect concentration(LOEC)of each toxicity index tested of D.magna decreased,indicating that the whole-life-stage exposure of pollutants might have greater environmental hazards to D.magna.To sum up,these results show that partial-life-stage exposure experiments of chemicals might underestimate environmental hazards of environmental pollutants.Therefore,it might be necessary to carry out the whole-life-stage exposure experiments of zooplanktons to assess environmental hazards of chemicals in the future.