Avoidance behaviour response and esterase inhibition in the earthworm, Lumbricus terrestris, after exposure to chlorpyrifos

Abstract

The avoidance response of earthworms to polluted soils has been standardised using a simple and low-cost test, which facilitates soil toxicity screening. In this study, the avoidance response of Lumbricus terrestris was quantified in chlorpyrifos-spiked soils, depending on the pesticide concentration and exposure duration. The inhibition of acetylcholinesterase (AChE) and carboxylesterase (CbE) activities was also determined as indirect measures of pesticide bioavailability. The effects of different chlorpyrifos concentrations were examined in a standardised test (two-chamber system) with 0.6, 3 and 15 mg/kg chlorpyrifos. A modification of the test involved a pre-exposure step (24, 48 or 72 h) in soils spiked with 15 mg/kg. In both protocols, earthworms were unable to avoid the contaminated soils. However, the esterase activities showed that all earthworms were exposed to chlorpyrifos. Acetylcholinesterase activity did not change in earthworms in the standardised behavioural test (0.58 ± 0.20 U/mg protein, mean ± SD; n = 72), whereas the CbE activity was significantly inhibited (62-87 % inhibition) in earthworms exposed to 3 and 15 mg/kg. In the modified test, earthworms had greatly inhibited AChE activity (0.088 ± 0.034 U/mg protein, n = 72), which was supported by reactivation of the inhibited enzyme activity in the presence of pralidoxime (2-PAM). Similarly, the CbE activity was significantly inhibited in earthworms with all treatments. This study suggests that the avoidance behaviour test for organophosphorus-contaminated soils could be supported by specific biomarkers to facilitate a better understanding of pesticide exposure and toxicity during this test.

Enzymes of Earthworm as Indicators of Pesticide Pollution in Soil

“…The CbE is secreted by earthworm in their gut lumen. In Lumbricus terrestris, chlorpyrifos (OP) has been shown to significantly inhibit the CbE activity [61].…”

Toxicity, bioaccumulation and metabolism of pesticides in the earthworm

“…Dichlorvos, paraoxon and chlorpyrifos were also potent inhibitors of CaEs through the soil exposure of L. terrestris. 136,137) The species-dependent inhibition of CaE activity by pirimiphos-methyl was examined, using a cylindrical soil microcosm. 31) This pesticide markedly decreased the CaE activity of E. andrei and moderately did so for L. rubellus, while a concentration-dependent response was observed for L. terrestris.…”

Chronic toxicity of commercial chlorpyrifos to earthworm Pheretima peguana

“…AChE activity has been routinely used as a tool to monitor nerve impulse transmission in non-target animals exposed to insecticides (Rao and Kavitha, 2004;Eamkamon , 2012;Martinez-Morcillo et al, 2013, Qi et al, 2013. Inhibition of AChE activity at the nerve-to-nerve and nerveto-muscle junctions will cause both muscarinic and nicotinic effects and are interpreted as signs of neurotoxicity that profoundly affects the survival of organisms (Rao and Kavitha, 2004).…”