'Different strokes for different folks': geographically isolated strains of Lymnaea stagnalis only respond to sympatric predators and have different memory forming capabilities.

Gaining insight into how natural trait variation is manifest in populations shaped by differential environmental factors is crucial to understanding the evolution, ecology and sensory biology of natural populations. We have demonstrated that lab-reared Lymnaea detect and respond to the scent of a crayfish predator with specific, appropriate anti-predator behavioral responses, including enhanced long-term memory (LTM) formation, and that such predator detection significantly alters the electrophysiological activity of RPeD1, a neuron that is a necessary site for LTM formation. Here we ask: (1) do distinct populations of wild Lymnaea stagnalis respond only to sympatric predators and if so, can these traits be quantified at both the behavioral and neurophysiological levels, and (2) does the presence of a non-sympatric predator elicit anti-predator behaviors including augmentation of LTM? We tested three different populations of wild (i.e. not lab-reared) snails freshly collected from their natural habitat: (1) polders near Utrecht in The Netherlands, (2) six seasonally isolated ponds in the Belly River drainage in southern Alberta, Canada and (3) a 20-year-old human-made dugout pond in southern Alberta. We found strain-specific variations in the ability to form LTM and that only a sympatric predator evoked anti-predatory behaviors, including enhanced LTM formation and changes in RPeD1 activity.

Comparing memory-forming capabilities between laboratory-reared and wild Lymnaea: learning in the wild, a heritable component of snail memory.

We set out to determine whether the ability to form long-term memory (LTM) is influenced by laboratory rearing. We investigated the ability of four populations of Lymnaea stagnalis to form LTM following operant conditioning both in the freely behaving animal and at the electrophysiological level in a neuron, RPeD1, which is a necessary site for LTM. We hypothesized that laboratory rearing results in a decreased ability to form LTM because rearing does not occur in an 'enriched environment'. Of the four populations examined, two were collected in the wild and two were reared in the laboratory--specifically, (1) wild Dutch snails; (2) their laboratory-reared offspring; (3) wild Southern Alberta snails (Belly); and (4) their laboratory-reared offspring. We found that Belly snails had an enhanced capability of forming LTM compared with Dutch laboratory-reared snails. That is, the Belly snails, which are much darker in colour than laboratory-reared snails (i.e. blonds), were 'smarter'. However, when we tested the offspring of Belly snails reared in the laboratory we found that these snails still had the enhanced ability to form LTM, even though they were now just as 'blond' as their laboratory-reared Dutch cousins. Finally, we collected wild Dutch snails, which are also dark, and found that their ability to form LTM was not different to that of their laboratory-reared offspring. Thus, our hypothesis was not proved. Rather, we now hypothesize that there are strain differences between the Belly and Dutch snails, irrespective of whether they are reared in the wild or in the laboratory.

Reconsolidation and memory infidelity in Lymnaea.

Lymnaea stagnalis were operantly conditioned to not perform aerial respiratory behaviour in a specific context (i.e. context-1). The memory for this learned response was reactivated 3 days later in context-1. During the 1 h reconsolidation period following memory reactivation, randomly picked snails were either maintained in context-1 or exposed to a new context (i.e. context-2). One hour later in the post-reconsolidation period, snails in context-1 were placed for 1 h in context-2 and vice-versa. In neither the hypoxic reconsolidation nor the post reconsolidation periods did snails receive a reinforcing stimulus when they opened their pneumostome. All snails were blindly tested for memory 24 h later period in context-2. Only those snails that had been exposed to context-2 during the reconsolidation period exhibited 'memory' for context-2. That is, memory infidelity was observed. Snails exposed to context-2 in only the post-reconsolidation period did not show memory for context-2. The immediate cooling of snails after their exposure to the new context in the reconsolidation period blocked the formation the implanted memory. Snails trained in context-1 and exposed to context-2 in the consolidation period only, also did not have memory for context-2. However, the memory for context-1 could still be recalled following successful implantation of the 'new' memory. All data presented here are consistent with the notion that during the reconsolidation process memory can be updated.

One-trial conditioning of aerial respiratory behaviour in Lymnaea stagnalis.

Repeated spaced training sessions of contingent tactile stimulation to the pneumostome as it opens are required to cause long-term memory (LTM) formation of aerial respiratory behaviour making if difficult to determine exactly when memory forms. We have devised a single-trial aversive operant conditioning training procedure in Lymnaea to be better able to elucidate the causal mechanisms of LTM formation. Observations of baseline breathing behaviour in hypoxia were first made. Twenty-four hours later the snails were trained using the single trial procedure, by placing them in a small Petri dish containing 4 ml of 25 mM KCl for 30-35s as soon as the first pneumostome opening in hypoxia was attempted. LTM was present if (1) breathing behaviour following training was significantly less than before; and (2) breathing behaviour post-training was significantly less in experimental groups than in yoked control groups. LTM persisted for 24 h but not 48 h. Yoked controls that received an aversive stimulus not contingent with pneumostome opening had no evidence of memory. Cooling directly after, but not at any other time, blocks LTM formation. LTM formation was also prevented by removal of the cell body of the neuron RPeD1 before training.