Abstract
The massive application of rare earth elements (REEs) in electronic industries cause their inevitable release into the environment; however, its effects on soil biota remain largely unaddressed. We investigated the E. fetida detoxification potential of nano and bulk La2O3 and Yb2O3 and their potential impact on biochemical and genetic markers at 50, 100, 200, 500 and 1000 mg kg- 1 concentration. We found that earthworms bioremediate 3-15% La2O3 and Yb2O3 contaminated soil at low and medium levels, while this potential was limited at higher levels. Nano and bulk La2O3 and Yb2O3 treatment induced neurotoxicity in earthworm by inhibiting acetylcholinesterase by 49-65% and 22-36% at 500 and 1000 mg kg- 1, respectively. Nano La2O3 proved to be highly detrimental, mainly through oxidative stress and subsequent failure of antioxidant system. Nano La2O3 and Yb2O3 at 100 mg kg- 1 significantly down-regulated the expression of annetocin mRNA in the parental and progeny earthworms by 50% and 20%, which is crucial for earthworm reproduction. Similarly, expression level of heat shock protein 70 (HSP70) and metallothionein was significantly upregulated in both generations at medium exposure level. Histological observations showed that nano REEs at 200 mg kg- 1 induced drastic changes in the intestinal epithelium and typhlosole of E. fetida. To date, our results enhance the understanding of interaction between REEs and earthworms.