Earthworms are renowned for serving as an important link in food webs. Recently, researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences found that earthworms also played an important role in trace element transfer.They found that earthworms helped transferring Selenium (Se), which is unevenly distributed across terrestrial landscapes.

Nowadays, the growing use of Se-containing fertilizers can exert influences on soil biota. Understanding the effect of Se on earthworms is conducive to assess the potential impact of Se on soil ecosystems, environmental safety, and human and animal health. However, information on the bioaccumulation of Se in earthworms is rather scarce.

The researchers studied the bioaccumulation of Se in two eco-physiologically different earthworms, namely anecic Pheretima guillemi and epigeic Eisenia fetida.

After 28 days exposure to a successive dose of Se-spiked soil, they found that the Se concentration in earthworms elevated with increasing exposure levels, and exposure to Se caused significant inhibition on earthworm growth, with the fresh weight loss ranging from 8.9% to 80.5%, after 4 weeks exposure to 200 mg Se g^-1 soil.

The results also demonstrated that bioaccumulation factors (BAFs), empirically-derived and non-steady state, generally declined at higher exposure levels.

In addition, BAFs of Pheretima guillemi were higher than those of Eisenia fetida in low-dose Se-spiked soils, and it was opposite in high-dose soils, indicating a species-specific response to exposure of Se between different earthworms.

These findings provide preliminary information on the uptake and bioaccumulation of selenite by different earthworm species, and further suggest the needs of characterizing the uptake and depuration kinetics of Se by a wider range of earthworm species other than Eisenia fetida.

Furthermore, the study published in Chemosphere allows a better risk assessment of excessive Se to soil invertebrates and higher order organisms.

The research was supported by the Science and Technology Major Project of Guangxi, the National Key Research and Development Program of China and the Chinese Academy of Sciences.

Contact: LI Dejun

E-mail: dejunli@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences

Little Earthworm(Imaged from https://pixabay.com)