Effect of temephos on cholinesterase activity in the earthworm Eisenia fetida (Oligochaeta, Lumbricidae)

In this study, adult Eisenia fetida earthworms were exposed to the sub-lethal concentrations of temephos using the contact filter paper test procedure. Since temephos is an organophosphate pesticide, its effects on earthworms were determined by measuring ChE inhibition—a known biomarker of exposure. The ChE activity was measured after a short time of exposure—1 and 2 h. As expected, the lowest ChE activity (72.70% and 38.03% inhibition) was measured at the highest concentration of temephos (120 ng cm−2) applied. More interestingly, at the 0.12 ng cm−2 concentration the ChE activity increased up to 36.28% of activity in the control in all three conducted experiments. Dose-response curves showed an inverted U-shape characteristic for hormesis. This hormetic-like effect could be important for health status of an earthworm.