Daily and seasonal changes in heat exposure and the Hsp70 level of individuals from a field population of Xeropicta derbentina (Krynicki 1836) (Pulmonata, Hygromiidae) in Southern France

Abstract

The Mediterranean land snail Xeropicta derbentina forms huge populations in Southern France. In order to characterize heat exposure and the induction of the 70-kD heat shock protein (Hsp70) response system during the life cycle of this snail, a selected population from the Vaucluse area, Provence, was investigated encompassing the issues of morphological life cycle parameters (shell size and colouration), the daily courses of heat exposure at different heights above the ground, of shell temperature, and that of the individual Hsp70 levels. The study covered all four seasons of the year 2011. Snails were found to be annual, reaching their final size in August. The shell colouration pattern showed high variation in juveniles (spring) with a strong tendency towards becoming uniformly white at old age in autumn. In all seasons, ambient air temperature decreased with increasing distance from the ground surface during daytime while remaining constantly low in the night. Overall, the Hsp70 level of individuals followed the ambient temperature during diurnal and seasonal variations. Correlation analysis revealed a positive association of individual shell temperature and Hsp70 level for the most part of the life cycle of the snails until late summer, whereas a negative correlation was found for aged animals indicating senescence effects on the capacity of the stress response system.

Hsp70 and lipid peroxide levels following heat stress in Xeropicta derbentina (Krynicki 1836) (Gastropoda, Pulmonata) with regard to different colour morphs

“…Among these pale individuals lower percentages of individuals were observed which were characterized by a darkly pigmented banding of the shell and which can be categorized according to the banding pattern described in previous studies (Di Lellis et al 2012;Dieterich et al 2012;Dittbrenner et al 2009;Köhler et al 2009). …”

“…In its adult state, X. derbentina reaches shell sizes up to 16 mm in diameter. This annual species (Dieterich et al 2012;Kiss et al 2005) can often be found in areas with scarce vegetation, at the borders of agricultural areas and along roads. The ability to climb vertical objects can not only be seen as a way to protect these snails from overheating in consequence of high ground temperatures, as postulated by different authors (Cowie 1985;Pomeroy 1968).…”

“…Most of the yet investigated populations of X. derbentina in Southern France were mainly characterized by individuals that carried a pure white shell (Dieterich et al 2012;Köhler et al 2009) when they have reached their final size. Among these pale individuals lower percentages of individuals were observed which were characterized by a darkly pigmented banding of the shell and which can be categorized according to the banding pattern described in previous studies (Di Lellis et al 2012;Dieterich et al 2012;Dittbrenner et al 2009;Köhler et al 2009).…”

“…Hsps are categorized according to their molecular weight, and best investigated is the 70 kDa family -Hsp70. As a marker of effect, Hsp70 has been frequently used in characterizing the molecular stress response of different organisms to heat and other stressors (Daugaard et al 2007;Dieterich et al 2012;Feder and Hofmann 1999;Köhler et al 2001;Mayer and Bukau 2005). However, some Hsp70 isoforms are also expressed under non-stress conditions.…”

“…It is known that different populations of a species can differ in their Hsp70 content and in their ability to induce Hsp70 as a response to heat, depending on their natural habitat and on the organisms' general ability of Hsp70 induction as, for example, shown in whole body homogenates of Drosophila sp flies (Bahrndorff et al 2006;Krebs and Feder 1997;Sørensen et al 2001). In case of X. derbentina, analyses of whole body homogenates have shown that the Hsp70 level of individuals depends on the population (Di , the life stage, the season, and the intensity of heat exposure (Dieterich et al 2012) as well as on the total load of heat stress over a given period of time Scheil et al 2011). Furthermore, was been shown that several populations of X. derbentina deriving from the same area have developed different heat response strategies characterized by different levels of Hsp70 (Troschinski et al 2014).…”