Seasonal cellular stress phenomena and phenotypic plasticity in land snail Helix lucorum (L.) populations from different altitudes.

Temperature, a major abiotic environmental factor, regulates various physiological functions in land snails and therefore determines their biogeographical distribution. Thus, species with different distributions may present different thermal tolerance limits. Additionally, the intense reactivation of snail metabolic rate upon arousal from hibernation or aestivation may provoke stress. Land snails, Helix lucorum, display a wide altitudinal distribution resulting in populations being exposed to different seasonal temperature variations. The aim of the present study was to investigate the expression of heat shock proteins (Hsps), mitogen activated protein kinases (MAPKs) and proteins that are related to apoptosis (Bcl-2, ubiquitin), that have "cytoprotective" roles and are also considered to be reliable indicators of stress because of their crucial role at maintaining cellular homeostasis. These proteins were assessed in H. lucorum individuals from two different populations, one at Axios (sea level, 0m) and the other one at Kokkinopilos (Olympus, 1250 m), as well as after mutual population exchanges. Therefore, this study aimed to answer whether the different responses of these stress-related proteins depend solely on the environmental temperatures. The results of the present study showed seasonally altered levels in all studied proteins in the hepatopancreas and foot of snails, as much among different populations as between the same populations being exposed to varying altitudes. However, the changes between individuals of the same population acclimatized to a different habitat, showed a relatively similar pattern of expression supporting the induction of the specific proteins under the prism of the life history of each species.