Selenium (Se) is an essential trace element for humans and animals. Its necessity for plants is still under examination. Due to the contradictory nature of Se and its significance, it has received much interest in recent years. Se deficiency can be harmful to humans, yet almost a billion people are deficient. Its deficiency has been associated with cancers, impairment of organs, and a number of other ailments. The biofortification of plants and livestock is a guaranteed practice to increase human selenium consumption. Strategies such as foliar spraying, the direct application of Se in plants and Se feed, and injections in livestock have been employed. Se biofortification has been shown to have additional beneficial effects in plants and livestock. In plants, it has been reported to mitigate different types of stress and increase yield. In animal biofortification, Se has been shown to reduce the detrimental effects of ailments and promote healthy growth. Se biofortification, nevertheless, confronts a number of difficulties. For instance, the bulk of biofortified products must be prepared before consumption, lowering the Se concentration. The objective of this review is to convey the current understanding of the Se biofortification of plants and animals, as well as its difficulties, taking into account both the detrimental consequences of Se deficiency and benefits of Se biofortification.

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, Caenorhabditis elegans and Acrobeloides 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), Caenorhabditis elegans and Acrobeloides 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 Acrobeloides sp. in ecotoxicological studies.