Tracking the path from learning to innate predator recognition in Lymnaea stagnalis

Organisms evolve adaptive strategies to adjust to the rapidly changing
environmental stressors. Predation pressure is one of the strongest
selective forces and organisms respond to predatory threats via innate and
learned responses. We utilized a natural, experimental set-up, where two
lakes –Stoney and Margo in Saskatchewan, Canada containing natural
populations of the prey Lymnaea stagnalis differed in the presence and
absence of an invasive, predatory Northern crayfish, Faxonius virilis. We
exploited the contrast in the predation backgrounds of the snail
populations from the two lakes to test, a) if predator-naïve snails learn
to detect a novel invasive predator, b) predator recognition in
predator-experienced snails is innate, and, c) if learning about a novel
predator gets transmitted to the successive generations. We quantified
predator fear memory formation using a higher-order learning paradigm
called configural learning. We found that a) predator-naïve snails learned
to recognize the novel predator even after a brief exposure to predator
cues highlighting the role of learning in combating invasive predators, b)
predator recognition in predator-experienced snails is innate, and, c) the
learning and predator detection mechanisms is not transmitted to
successive generations. The population variation observed in the
predator-detection mechanism may be due to the activation and deactivation
of a predatory template as a function of predator exposure in the
environment. We find an interesting study system to address how fear
learning occurs and the possible mechanism of the formation of innate fear
recognition from a learned fear recognition.