Juveniles of Lymnaea smart snails do not perseverate and have the capacity to form LTM

2019

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Ecologically relevant stressors alter the ability of the pond snail, Lymnaea stagnalis, to form long-term memory (LTM). Here, we show that an environmentally relevant stressor, shell damage, has a dramatic effect on the enhancement of LTM formation. Damage in the form of a shell clip 24 h before operant conditioning training resulted in long-term memory (LTM) formation following a single 0.5 h training session (TS). Typically, in these snails, two 0.5 h TSs with a 1 h interval between the sessions are required to cause LTM formation. We show here that even with a 72 h interval between shell clip and training, memory enhancement still occurred. The stress associated with shell clip could be mitigated by an ongoing high-Ca 2+ pond water environment, an injection of propranolol and a DNA methylation blocker. However, use of an anaesthetic (MgCl 2) during the clip or intermittent exposure to the high-Ca 2+ pond water environment did not mitigate the stress associated with the shell clip. Shell clip was also sufficient to cause juvenile snails, which neither learn nor form memory, to gain the capacity to form LTM. Together, the experiments demonstrate that shell clipping is an environmentally relevant stressor that can cause enhancement of LTM formation.

Section: Resultsmentioning

confidence: 99%

Shell damage leads to enhanced memory formation in Lymnaea

Swinton

2019

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“…Memory-forming ability has also been shown to change across the lifespan of some L. stagnalis strains. Specifically, in L. stagnalis strains demonstrating an average memory-forming ability (both lab-bred and collected from the wild), juveniles are unable to form LTM, but this is overcome by development into adulthood (McComb et al, 2005;Shymansky et al, 2017). In addition, it has been demonstrated that the ability of the lab-bred C-strain snails to form LTM is compromised with age when they are trained with an appetitive conditioning paradigm (Hermann et al, 2007;Watson et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…The memory-forming ability of juvenile L. stagnalis has previously been examined in both average strains (the lab-bred C-strain as well as wild strains; McComb et al, 2005;Shymansky et al, 2017) and smart wild L. stagnalis strains . Juvenile L. stagnalis from average strains demonstrate an inability to form LTM, which is overcome by development into adulthood (McComb et al, 2005;Shymansky et al, 2017). However, juveniles from two different smart wild strains have been shown to possess the same memory-forming ability as adults from these populations.…”

Section: The Adult Transformed B-strain Still Forms Ltm When Challengmentioning

confidence: 99%

“…The smart phenotype has previously only been observed in juvenile and adult animals from strains collected in the wild , while the average ability has been reported in both wild and lab-bred populations. Interestingly, juveniles belonging to an average strain are unable to form LTM, but this inability is overcome by predator detection as well as development into adulthood (McComb et al, 2005;Orr et al, 2010;Forest et al, 2016;Shymansky et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Strain transformation: Enhancement of invertebrate memory in a new rearing environment

Rothwell

2019

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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.

“…There is a heritable component to the different memory-forming abilities in L. stagnalis, as the differences observed between freshly collected 'wild' strains are maintained in their lab-bred offspring (Orr et al, 2009a;Dalesman et al, 2011c;Shymansky et al, 2017). Moreover, memory enhancement, triggered, for example, by the detection of a predator, is obstructed by application of a DNA methylation inhibitor.…”

Section: Introductionmentioning

confidence: 99%

The effect of rearing environment on memory formation

Rothwell

Spencer

2018

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is a well-studied model system for determining how changes in the environment influence associative learning and memory formation. For example, some wild strains of , collected from separate geographic locations, show superior memory-forming abilities compared with others. Here, we studied memory formation in two laboratory-bred strains, derived from the same original population in The Netherlands. The two strains were reared in two different laboratories at the University of Calgary (C-strain) and at Brock University (B-strain) for many years and we found that they differed in their memory-forming ability. Specifically, the C-strain required only two training sessions to form long-term memory (LTM) whereas the B-strain required four sessions to form LTM. Additionally, the LTM formed by the B-strain persisted for a shorter amount of time than the memory formed by the C-strain. Thus, despite being derived from the same original population, the C- and B-strains have developed different memory-forming abilities. Next, we raised the two strains from embryos away from home (i.e. in the other laboratory) over two generations and assessed their memory-forming abilities. The B-strain reared and maintained at the University of Calgary demonstrated improved memory-forming ability within a single generation, while the C-strain reared at Brock University retained their normal LTM-forming ability across two subsequent generations. This suggests that local environmental factors may contribute to the behavioural divergence observed between these two laboratory-bred strains.