| Abstract: | The degree of inhibition and the rate of recovery of total cholinesterase level were investigated after in-vivo treatment of the earthworm Eisenia foetida (Savigny) with aldicarb, carbaryl, carbofuran, oxamyl, and the O-analogues of bromophos (bromo-phosoxon), parathion (paraoxon), parathion-methyl (paraoxon-methyl), and trichloronate (trichloronatoxon). The results can be explained by the presence of two cholinesterases (E1 and E2), which were demonstrated by in-vitro inhibition studies. E1 was the most sensitive to all the inhibitors tested. The in-vivo reactivation rate after inhibition with paraoxon was very high for E1 and very low for E2. Therefore, pretreatment with paraoxon probably increased the toxicity of carbaryl. It was concluded that the toxicity towards E. foetida can be explained in terms of cholinesterase inhibition, provided that the action on the two cholinesterases and the worms' tolerance for a transient but almost total cholinesterase depression are taken into account. Data are given showing that two other species of earthworms also contain different types of cholinesterases with respect to reactions with inhibitors. |
