Strain transformation: enhancement of invertebrate memory in a new rearing environment.

Memory formation is influenced by a variety of factors, including the environmental conditions in which an organism is reared. Here, we studied the memory-forming ability of the lab-bred B-strain of Lymnaea stagnalis following a change in their rearing environment from Brock University to the University of Calgary. We have previously demonstrated that this move enhances memory-forming ability and here we studied the magnitude of this phenotypic change. Once reared to adulthood at the University of Calgary, the B-strain animals were first tested to determine how many training sessions were required for the formation of long-term memory (LTM) to occur. Following the change in environment, the B-strain transformed into a 'smart' lab-bred strain requiring only a single 0.5 h session to form LTM. Next, we tested whether exposure to physiologically relevant stressors would block the formation of LTM in this 'transformed' B-strain, as this obstruction has previously been observed in 'smart' snails collected from the wild. Interestingly, neither stressor tested in this study perturbed memory formation in this transformed lab-bred strain. Additionally, both the smart memory phenotype and increased stress resilience were observed in the second generation of transformed B-strain animals at both juvenile and adult stages. This suggests that a change in rearing environment can contribute to the memory-forming ability of lab-bred L. stagnalis.