Responses of Enchytraeus albidus (Clitellata: Enchytraeidae) to changes in soil water potential

Enchytraeids (‘pot worms' or ‘white worms') are widespread soil-dwelling organisms facing increasing threats from climate change. The aim of this study was to investigate how drought affects the physiology, life cycle parameters, and behavior of the enchytraeid Enchytraeus albidus . The effects of soil moisture on adult worms were tested at soil water contents ranging from 6% to 24% of dry weight, corresponding to soil water potentials (SWP) from −236 kPa to −1.8 kPa. A suite of experiments assessed the effects of these moisture levels on behavioral avoidance, feeding activity, body water content, survival, and reproduction. Using a regression approach, we established the SWP causing a 50% performance decrease (SWP 50 ) relative to the optimal SWP. Feeding activity was the most sensitive trait (SWP 50 = −4 kPa) followed by reproduction (3 weeks; SWP 50 = −6 kPa) and survival (3 weeks; SWP 50 = −23 kPa). Body water content of adults decreased significantly with decreasing soil moisture indicating the physiological stress inflicted by a decreasing SWP. Reduced body water content was likely the main physiological signal leading to mortality and cessation of both feeding and reproduction. This study highlights the importance of understanding the physiological and behavioral adaptations of enchytraeids, as well as their ecological functions for effective soil management and development of strategies to mitigate the negative effects of climate change on soil fauna communities.