Toxic effects of chlorpyrifos on morphology and acetylcholinesterase activity in the earthworm, Eisenia foetida.

The acute toxicity of chlorpyrifos (O, O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) was determined in the earthworm, Eisenia foetida. A 48-h contact test as described by the Organization for Economic Cooperation and Development (OECD) guideline 207 was carried out. The LC(50) of chlorpyrifos was 0.063 microg/cm(2). Inhibition of acetylcholinesterase (AChE: EC 3.1.1.7) activity indicated by in vitro neurotoxic potentiality revealed competitive inhibition and altered K(m) values widely in a dose-dependent manner. The K(i) value of chlorpyrifos was 4.20 x 10(-6)M. AChE activity of LC(50)-exposed worms was 62%, 79%, 85%, and 91% inhibited at 12, 24, 36, and 48h, respectively. Scanning electron microscopic studies revealed the morphological abnormalities in the worms. The present study demonstrates a dose- and time-dependent exposure of chlorpyrifos through skin results, morphological abnormalities, and inhibition of AChE in the earthworm, E. foetida.