Abstract
The Mediterranean snail Xeropicta derbentina, being highly abundant in Southern France, has the need for efficient physiological adaptations to desiccation and over-heating posed by dry and hot environmental conditions. In consequence of heat, oxidative stress manifests in these organisms, which, in turn, leads to the formation of reactive oxygen species (ROS). In this study, we focused on adaptations on the biochemical level by investigation of antioxidant defenses and heat shock protein 70 (Hsp70) induction, both essential mechanisms of the heat stress response. We exposed snails to elevated temperature (25, 38, 40, 43, and 45°C) in the laboratory and measured the activity of the antioxidant enzymes catalase (CAT) and glutathione peroxidase (GPx), determined the Hsp70 level, and quantified lipid peroxidation. In general, we found a high constitutive level of CAT activity in all treatments, which may be interpreted as a permanent protection against ROS, i.e. hydrogen peroxide. CAT and GPx showed temperature-dependent activities: CAT activity was significantly increased in response to high temperatures (43 and 45°C), whereas GPx exhibited a significantly increased activity at 40°C, likely in response to high levels of lipid peroxides which already occurred in the 38°C treatment. Hsp70 showed a maximum induction at 40°C, followed by a decrease at higher temperatures. Our results reveal that X. derbentina possesses a set of efficient mechanisms to cope with damaging effects by heat. Furthermore, we could demonstrate that, beside the well documented Hsp70 stress response, the antioxidant defense plays a crucial role in these snails competence to survive extreme temperatures.
