Bio-interaction of nano and bulk lanthanum and ytterbium oxides in soil system: Biochemical, genetic, and histopathological effects on Eisenia fetida

Highlights: • Earthworms had a limited potential to detoxify nano/bulk REEs (La₂O₃ and Yb₂O₃) in soil. • Both REEs had a significant effect on the biochemical markers of E. fetida. • Both REEs inflicted physiological damage to the digestive system of earthworms. • Annetocin gene involved in reproduction was significantly affected in progeny by nano REEs. 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.