Mortality, growth and metabolic responses by 1H-NMR-based metabolomics of earthworms to sodium selenite exposure in soils

The rapid development of selenium-enriched agriculture leads to the accumulation of selenium in the soil, which has an adverse impact on terrestrial ecosystems. In the present study, the mortality, growth inhibition rate and metabolism of earthworms were examined to investigate the toxicological effects of sodium selenite (Na2SeO3) on earthworms (Eisenia fetida) after exposuring for 14 days (d). We used H-1-NMR-based metabolomics to identify sensitive biomarkers and explored the metabolic responses of earthworms exposed to Na2SeO3. The mortality and growth inhibition rate of earthworms exposed to 70 and 90 mg/kg Na2SeO3 were significantly higher than the rate of control group. The LC50 (the median lethal concentration) of Na2SeO3 was 57.4 mg/kg in this artificial soil test of E. fetida exposed to Na2SeO3 for 14 d. However, there was no significant differences when earthworms were exposed to different concentrations of Na2SeO3. The selected metabolic markers were ATP, lactic acid, leucine, alanine, valine, glycine, glutamic acid, lysine, alpha-glucose and betaine. Na2SeO3 affected the metabolic level of earthworms, as the percentage of metabolic markers in the earthworm changes when exposed to different concentrations of Na2SeO3. The metabolic disturbances were greater with increasing concentrations of Na2SeO3. The differential metabolic markers were significantly changed when exposed to Na2SeO3 comparing to those in the control group, affecting the tricarboxylic acid cycle process and breaking the metabolic balance. This study showed that Na2SeO3 had toxic effect on the growth and development of earthworms. In addition, this study provided a biochemical insights for the development of selenium-enriched agriculture.