Agricultural use of insecticides alters homeostatic behaviours and cognitive ability in Lymnaea stagnalis.

Lymnaea stagnalis is an ecologically important, stress-sensitive, freshwater mollusc that is at risk for exposure to insecticides via agricultural practices. We provide insight into the impact insecticides have on L. stagnalis by comparing specific behaviours including feeding, locomotion, shell regeneration, and cognition between snails collected at two different sites: one contaminated by insecticides and one not. We hypothesized that each of the behaviours would be altered in the insecticide-exposed snails and that similar alterations would be induced when control snails are exposed to the contaminated environment. We found no significant differences in locomotion, feeding and shell regeneration of insecticide-exposed L. stagnalis compared to non-exposed individuals. Significant changes in feeding and shell repair were observed in non-exposed snails inhabiting insecticide-contaminated pondwater. Most importantly, snails maintained and trained in insecticide-contaminated pondwater did not form configural learning but this cognitive deficit was reversed when these snails were maintained in insecticide-free pondwater. Our findings conclude that insecticides have a primarily negative impact on this higher form of cognition in L. stagnalis.