Abstract
Telomeres, the protective, terminal parts of the chromosomes erode during cell division and as a result of oxidative damage by reactive oxygen species (ROS). Ectotherms rely on the ambient temperature for maintaining temperature-dependent metabolic rate, regulated through behavioural thermoregulation. Their temperature-dependant metabolism, hence also the ROS production, is indirectly regulated through thermoregulation. Consequently, a potential causal chain affecting telomere length and attrition is: temperature (in particular, its deviation from a species-specific optimum) – metabolism - ROS production – anti-oxidation - telomere erosion. We measured telomere length in sand lizards (Lacerta agilis) using qPCR on blood samples from 1998–2006. Effects of climatological parameters (mean temperature and average sunshine hours) in the summer and winter preceding telomere sampling were used as predictors of telomere length in mixed model analysis. During the lizards’ active period (summer), there was a largely negative effect of mean temperature and sun on telomere length, whereas a combined measure of age and size (head length) was positively related to telomere length. During the inactive period of lizards (winter), the results were largely the opposite with a positive relationship between temperature and sunshine hours and telomere length. In all four cases, thermal and age effects on telomere length appeared to be non-linear in the two sexes and seasons, with complex response surface effects on telomere length from combined age and thermal effects.
Highlights
Telomeres, the protective, terminal parts of the chromosomes erode during cell division and as a result of oxidative damage by reactive oxygen species (ROS)
Thermal shifts restrain the oxygen delivery system and ROS production increases during heat stress, telomere erosion is elevated by a rise in temperature, at least in some taxa[8]
Understanding telomere dynamics in free-living populations is crucial to understanding their role in evolutionary and ecological processes, especially their role in mediating life-history trade-offs
Summary
The protective, terminal parts of the chromosomes erode during cell division and as a result of oxidative damage by reactive oxygen species (ROS). A potential causal chain affecting telomere length and attrition is: temperature (in particular, its deviation from a species-specific optimum) – metabolism - ROS production – anti-oxidation - telomere erosion. Thermal shifts restrain the oxygen delivery system and ROS production increases during heat stress, telomere erosion is elevated by a rise in temperature, at least in some taxa[8]. Given the potential causal chain, temperature – metabolism – ROS production – anti-oxidation - telomere erosion, ectotherm telomere dynamics should be affected by climatic effects during the time of year when lizards are active and bask to elevate their body temperature[9,24,25,26]. In some endotherms that act as ectotherms in the sense of clearly differentiated seasonal activity and major metabolic shifts (i.e. torpor), studies have shown a relationship between hibernation and telomere lengths. The season-dependent telomere dynamic in response to dramatic metabolic changes with time of year in these small rodents raises the question whether similar dynamics play out in reptilian ectotherms
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