Interaction between environmental stressors mediated via the same sensory pathway.

The great pond snail, Lymnaea stagnalis, is a calciphile, requiring approximately 20 mg/l dissolved calcium for natural populations to live long and prosper. However, despite population survival we have previously demonstrated that acute exposure for 1 week to low environmental calcium (20 mg/l) acts as a stressor on the snail, blocking long-term memory (LTM) formation. This response to calcium availability is mediated by the snail directly sensing the calcium concentration in its environment using a sensory structure called the osphradium. In addition to sensing the calcium environment, the osphradium also mediates the response to predator kairomones which has an opposite effect on memory i.e. kairomone exposure during training enhances LTM formation. Here we demonstrate how these two stressors (low calcium availability and predator kairomones), that alter memory formation in opposing directions via the same sensory system, interact when experienced simultaneously.