Data from: Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes

Life history strategies vary dramatically between the sexes, which may drive divergence in sex-specific senescence and mortality rates. Telomeres are tandem nucleotide repeats that protect the ends of chromosomes from erosion during cell division. Telomeres have been implicated in senescence and mortality because they tend to shorten with stress, growth and age. We investigated age-specific telomere length in female and male red-sided garter snakes, Thamnophis sirtalis parietalis. We hypothesized that age-specific telomere length would differ between males and females given their divergent reproductive strategies. Male garter snakes emerge from hibernation with high levels of corticosterone, which facilitates energy mobilization to fuel mate-searching, courtship, and mating behaviours during a 2-4 week aphagous breeding period at the den site. Conversely, females remain at the dens for only about four days and seem to invest more energy in growth and cellular maintenance, as they usually reproduce biennially. As male investment in reproduction involves a yearly bout of physiologically stressful activities, while females prioritise self-maintenance, we predicted male snakes would experience more age-specific telomere loss than females. We investigated this prediction using skeletochronology to determine the ages of individuals and qPCR to determine telomere length in a cross-sectional study. For both sexes, telomere length was positively related to body condition. Telomere length decreased with age in male garter snakes, but remained stable in female snakes. There was no correlation between telomere length and growth in either sex, suggesting that our results are a consequence of divergent selection on life histories of males and females. Different selection on the sexes may be the physiological consequence of the sexual dimorphism and mating system dynamics displayed by this species.

两性的生活史策略差异极大，这可能驱动性别特异性衰老与死亡率的分化。端粒（telomere）是一类串联核苷酸重复序列，可保护染色体末端在细胞分裂过程中免受侵蚀。鉴于端粒会随应激、生长及年龄增长逐渐缩短，其已被证实与衰老及死亡率密切相关。本研究针对雌性与雄性红边束带蛇（Thamnophis sirtalis parietalis）的年龄特异性端粒长度展开探究。基于二者迥异的繁殖策略，我们提出假设：雌雄个体的年龄特异性端粒长度存在差异。雄性红边束带蛇冬眠苏醒时皮质酮（corticosterone）水平较高，该激素可促进能量调动，以支撑它们在巢穴所在地为期2至4周的禁食繁殖期内，开展求偶搜索、求偶行为与交配活动。与之相对，雌性仅会在巢穴停留约4天，且似乎将更多能量投入生长与细胞维持——这是由于它们通常每两年繁殖一次。由于雄性繁殖需每年经历一轮生理应激活动，而雌性优先进行自我维持，我们预测雄性红边束带蛇的年龄特异性端粒丢失程度将高于雌性。本研究采用横断面研究设计，通过骨骼年龄测定法（skeletochronology）确定个体年龄，并借助定量聚合酶链式反应（qPCR）测定端粒长度，以此验证上述预测。结果显示，无论雌雄，端粒长度均与身体状况呈正相关。雄性红边束带蛇的端粒长度随年龄增长而缩短，而雌性的端粒长度则保持稳定。无论雌雄，端粒长度与生长均无相关性，这表明本研究结果是雌雄两性生活史受到差异化选择的产物。该物种所展现的性别二态性与交配系统动态，或正是两性间差异化选择带来的生理效应。