Toxicity effect of Chlorpyrifos 50% + Cypermethrin 5% EC to terrestrial invertebrate Eisenia fetida in two different sphagnum peat substituted soil was assessed. Artificial soil substrate for earthworm toxicity test comprises of 70% sand, 20% clay and 10% sphagnum peat. In this study, coco peat was used as an alternative substitute for sphagnum peat. The LC50 was 83.7 mg/kg for coco peat and 76.3 mg/kg for sphagnum peat soil. No significant difference was observed in mortality and biomass between the two soil substrates, but a significant difference was observed in the reproduction. Based on the observations, it is concluded that coco peat can also be used as an alternative to sphagnum peat in toxicity studies.

The impact of two organophosphorus insecticides [Chlorpyrifos (CPF) and Monocrotophos (MCP)] on non-target wild natural gastropod, Pila globosa (apple snail) from the paddy fields was studied. The activity of acetylcholinesterase (AChE) was monitored on foot-muscle and hepatopancreas tissues of control and exposed snails. In the foot- muscle AChE inhibition progressed and reached 54.19% and 63.13% of the control, whereas, the AChE inhibition in the hepatopancreas reached 46.96% and 53.67% over control after 48 hours of exposure to 1.5 mL.L-1 and 2.5 mL.L-1 CPF respectively. After 48 hours of MCP exposure at 1.5 mL.L-1 and 2.5 mL.L-1 separately, the AChE inhibition of foot muscle was 49.07% and 57.59% respectively while in hepatopancreas it was 44.65% and 48.84% respectively. Our results show more inhibition of AChE activities on the foot-muscle than hepatopancreas in a concentration and time-dependent manner with greater severity by CPF in comparison to MCP. AChE inhibition increased with the increasing exposure time.