Extracellular pesticide detoxification in the gastrointestinal tract of the earthworm Aporrectodea caliginosa

• High level of carboxylesterase activity was found in the gastrointestinal lumen.
• Luminal carboxylesterases were efficient binding proteins for chlorpyrifos-oxon.
• The gastrointestinal tract is a potential extracellular detoxification system.

We provide evidences that indicate Aporrectodea caliginosa detoxifies extracelullarly organophosphorus (OP) pesticides through its digestive system. A high carboxylesterase activity (a group of esterases able to bind OP pesticides) was found in the luminal microenvironment of its gastrointestinal tract compared to casts (faeces) or bulk soil. In vitro inhibition kinetics and microcosm trials showed that this luminal CbE activity was highly sensitive to inhibition by chlorpyrifos-oxon. Our data suggest that CbE activity was an efficient bioscavenger for OP pesticides during gastrointestinal transit of soil, which increases our understanding of how earthworms are able to tolerate OP-contaminated soils.