Relationship between Toxicokinetics of Carbaryl and Effect on Acetylcholinesterase Activity in Pomacea patula Snail

The 96-h LC50 value of carbaryl was 14.6 μg/mL for the snail Pomacea patula. Organisms were exposed for 72 h to a low sublethal concentration (0.1 of LC50) using a semistatic contamination system; bioconcentration and elimination experiments were performed evaluating simultaneously acetylcholinesterase (ACHase) activity. The inhibition of the digestive gland ACHase reached 76% when the carbaryl concentration in tissue was 3.2 μg/g. The increased enzyme inhibition was observed concomitantly with the bioconcentration of carbaryl until 7 h. ACHase inhibition was linearly dependent on the uptake and bioconcentration of carbaryl (r2=0.87). The transfer of snails to carbaryl-free water after 72 h of exposure was followed by rapid monophasic elimination with a half-life of 1.0 h. However, ACHase activity levels never returned to control values. These results revealed that the bioconcentration might play a critical role in contributing to the toxicity of carbaryl.