Ecological Toxicity Of Antimony To Earthworm Eisenia Fetida

Various industrial applications can be found for antimony（Sb）.China has the largest reserves of Sb in the world,accounting for 55%of the world’s total Sb production.Sb has been released into the soil environment due to the widespread use of Sb-products and Sb mining activities.Considering the toxicity and bioavailability of Sb,soil organisms may be threatened by this contamination,disrupting their ecological functions.Considerable work has been done on Sb ecotoxic effects in plants and microorganisms,compared with relatively limited studies involving soil animals.Earthworms are indicator organism that helps evaluate soil quality due to its role in maintaining the soil ecosystem.A better understanding of Sb’s toxic effects and mechanisms on typical soil organisms like earthworm is still needed.Therefore,this paper selected Eisenia fetida as the test organism and exposed it to 0,10,50,100,250 and 500 mg/kg Sb-contaminated soil for 7 days.Then the pattern of Sb accmumlation along with earthworms’behavior,physiological and biochemical responses under different concentrations of Sb stress were invetigated.To gain a deeper understanding of the toxic effect and detoxification strategy of Sb for earthworms,bioinformatics was employed to screen out differentially expressed genes（DEGs）of earthworms under the stress of Sb.Following are the main research conclusions:（1）A significant effect of Sb was observed on earthworm burrowing behavior as well as their escape behavior.Following the third day of the burrowing test,the difference in cumulative burrowing lengths between treatments gradually increased,and a difference analysis revealed that the cumulative burrowing lengths of the 100 mg/kg,250 mg/kg,and 500mg/kg treatment on the 7th day were significantly greater than the 0 mg/kg and 10 mg/kg treatment.A 7-day avoidance test also showed an increase in earthworm avoidance behavior at250 mg/kg and 500 mg/kg.（2）Pearson correlation analysis showed that the accumulation of Sb in earthworm increased with the increase of Sb concentration,and the weight change rate and survival rate were significantly affected by Sb.Within a certain concentration range（≤100 mg/kg）,we found that earthworms can strengthen their defence systems（e.g.,antioxidant,detoxification and immune systems）to counter Sb toxicity so that their health and performance can be sustained.While GST could continue to function when the rest of the defense system’s enzyme activity was reduced,the detoxification process consumed more energy than the body needs for normal metabolism,resulting in a significant decrease in earthworm body weight at 250 mg/kg and 500mg/kg.Furthermore,the inactivation of calcium pump(Ca²⁺-ATPase)under Sb stress may be responsible for earthworm acetylcholinesterase（ACh E）activity.Since ACh E is essential for animal nerve transmission,the increased activity of ACh E may strongly influence earthworm burrowing behavior.Along with the results of the avoidance test,earthworms’increased burrowing behavior was also a stress response to escape severely damaged habitats.（3）At environmentally relevant concentration（50 mg/kg）,1178 differentially expressed genes（DEGs）were significantly up-regulated and 3832 down-regulated in earthworms.KEGG enrichment analysis shows that DEGs were mainly involved in nutrient digestion and absorption（protein digestion and absorption pathway,vitamin digestion and absorption pathway）,inflammation and its signal transduction（arachidonic acid metabolism pathway,PI3K-Akt signaling pathway）,detoxification（ABC transporter pathway）and pathways related to body homeostasis maintenance（renin-angiotensin-aldosterone system,blood coagulation system,vascular smooth muscle contraction）.At the transcriptional level,Sb intake may lead to intestinal microecology imbalance in earthworms,stimulate intestinal tissue and cause inflammation.The regeneration of intestinal mucus and anti-inflammatory factors helps earthworms repair their own intestinal damage and improve their ecological adaptability.Earthworms may,however,be limited in their ability to detoxify Sb and maintain calcium homeostasis as a result of suppressed expression of transporter genes on cell membrane.This eventually leads to cytotoxicity and can threaten their long-term survival in adverse environments.In summary,earthworms can cope with Sb stress through their own defense system and maintain their valuable ecological functions.Earthworms will cease to provide ecological services if Sb concentrations in the soil environment threaten their health.Sb toxicity mechanisms to earthworms were revealed in this study,providing useful information for soil ecological risk assessment and theoretical support for prevention and remediation.