Respon of earthworm burrowing behaviour as a biomarker of imidacloprid in soil

Abstract

This research was conducted to study the effect of imidacloprid on the burrowing behaviour of three earthworm species. Eiseniafoetida, Lumbricus rube/Ius and Pheretima asiatica. Furthermore, tllis research was also to study the possibility of using the behaviour as a biomarker of imidacloprid toxicity in its sublethal concentrations. The applied concentrations were 0, 1.25, 0.5, 0.75, and 1.0 mglkg dry weight soil (ppm) for the first two species, and 0, 1.5, 3.0, and 4.5 mg/kg dry weight soil (ppm) for P. asiatica, each with three replicates. Glass terraria of si ze 40 em x 30 em x 5 nun were used to observe their activities. After seven days of experiment, imidacloprid effects on burrowing behaviour was clearly visible, especially at t11e two llighest concentrations indicated by shorter burrows than those in the control. In addition, it was observed that burrowing activities were reduced with exposure time. Tllis was indicated by the distance covered which is shorter t11an that of the control. Among the tlrree species employed in tl1is study, L. rubellus is tl1e most sensitive species to the toxicity of imidacloprid. Effect of imidacloprid can be seen from burrowing pattern or topology as well. After t11e exposure, the burrowing topology of the worms was narrower than tl1e control. Based on these results, burrowing activities of the eart11worms are very potential to be used as biomarkers of imidacloprid toxicity.