Na2SeO3 Exposure Inhibits Locomotion and Reproduction via Oxidative Stress Mechanism in Bioindicators C. elegans and Acrobeloides sp.

Selenium (Se) fertilizers are widely used in Se biofortification. However, excessive application of Se fertilizers can easily cause soil Se accumulation and threaten soil organisms, so it is necessary to carry out research on the effects of Se on single species, especially on indigenous organisms in soil. In this study, as significant bioindicators, <i>Caenorhabditis elegans</i> and <i>Acrobeloides</i> sp. were used as research subjects to explore the effects of short-term Se exposure on the total Se content, Se speciation, and physiological and biochemical functions in nematodes. The results showed that total Se content in both nematodes increased significantly with higher Se exposure concentrations, and Se mainly exists in the speciation of selenomethionine (SeMet) and selenocysteine (SeCys₂). Exposed to high concentrations of Na₂SeO₃ (≥3 mg/kg), <i>Caenorhabditis elegans</i> and <i>Acrobeloides</i> sp. were strikingly inhibited in their locomotion and reproduction, and oxidative stress response was induced, which showed a significant increase in ROS, MDA, and SOD. Pearson correlations suggested a depressant effect on nematodes by oxidative stress mechanism. This study provides an important basis for the soil ecotoxicity assessment of Se and highlights the unique value of <i>Acrobeloides</i> sp. in ecotoxicological studies.