Response and defense mechanisms of the earthworms Eisenia foetida to natural saline soil stress.

Salinization of soil is a serious global environmental issue, particularly in agricultural lands. Saline farmland not only endangers grain production but also affects the survival of soil fauna. Earthworms, as soil ecosystem engineers, play a crucial role in maintaining soil health and enhancing global agricultural production. However, the response of earthworms to natural saline soil stress remains poorly understood. To explore this, we investigated the effects of natural saline soil from Dongying City, Shandong Province, China, on the growth, survival, reproduction, antioxidation, and defense-related gene expression of the earthworm Eisenia foetida. Our findings demonstrate that the growth rate, survival rate, and cocoon production of E. foetida decrease under exposure to natural saline soil in a dose-dependent manner. Elevated levels of DNA damage in coelomocytes and increased reactive oxygen species (ROS) were observed. Additionally, antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), increased under stress. The mRNA levels of Cyp450 and Hsp70 also rose in response to saline soil exposure. Furthermore, the activity of Na/K-ATPase and the expression of the osmotic sensor gene wnk-1 were elevated. In conclusion, our findings indicate that natural saline soil induces antioxidant and osmotic stress in earthworms E. foetida, highlighting the detrimental effects and defense mechanisms of soil fauna under such conditions.