| Summary: | Long-acting inhibitors of acetylcholinesterase (AChE) are used in large amounts as insecticides in agriculture, and are thereby introduced into the evironment. By incubating golden apple snails in chlorpyrifos, dichlorvos, or carbaryl, we determined the LD50’s to 3.7, 4.5 and 49 µM, respectively. AChE activities were measured in several organs; the highest activity was found in the gills. Following incubation in either of the three insecticides, the ED50’s for AChE inhibition in the gills were 0.37 µM, 0.22 µM, and 14 µM, respectively; there were no sex differences, but AChE inhibition was more marked in larger snails than in smaller ones, and incubation at 32 °C brought about a higher AChE inhibition than at 27 °C. The time course of AChE inhibition was studied in snails incubated at ED50 with either of the inhibitors. There was a 50% enzyme inhibition after about 6 min, 5 min, and 7 min, respectively. After 96 h incubation, enzyme inhibiton reached about 90% in all three groups. Following this exposure to inhibitor, the snails were transferred to fresh water; after 30 days there was virtually no recovery of AChE actvity in the snails exposed to chlorpyrifos or dichlorovos, whereas about 20% was recovered in snails exposed to carbaryl.
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