Data from: Individual differences in torpor expression in adult mice are related to relative birth weight

Daily torpor is a physiological adaptation in small mammals and birds, characterised by drastic reductions in metabolism and body temperature. Energy-constraining conditions, such as cold and starvation, are known to cause the expression of daily torpor. However, the reason for high degrees of inter- and intra- individual variation in torpor expression (TE) in similar situations is not clear. As littermates of altricial animals are exposed to an uneven allocation of maternal resources from conception to weaning, we tested whether early nutritional experiences have long-term effects on TE in adults. We used full-sibling littermates of laboratory mice that as adults were starved overnight to induce torpor. We measured body weight from birth until adulthood as an indicator of nutritional status, and calculated the relative body weight (RBW) as an indicator of the difference in nutritional status within a litter. After maturation, we subjected mice to five repeated torpor induction trials involving 24 hours of fasting and 5 days of recovery. Half of the female mice displayed great individual variation in TE, whereas male mice rarely exhibited daily torpor. In females, RBW at birth influenced TE, irrespective of body weight in adulthood; thus, female mice born with low RBWs displayed high TE in adulthood. In conclusion, we provide evidence that TE in mice differs among littermates, and that this variation is linked closely to heterogeneous nutritional experiences during the foetal period.日常蛰伏（Daily Torpor）是小型哺乳类与鸟类的一类生理适应机制，其核心特征为新陈代谢速率与体温的急剧降低。已知能量限制条件（如低温与饥饿）可诱发日常蛰伏的表达。然而，在相似环境条件下，蛰伏表达（Torpor Expression, TE）的个体间与个体内差异幅度较大，其潜在成因至今尚未明确。由于晚成动物的同窝幼崽自受孕至断奶阶段，会遭遇母源资源分配不均的情况，本研究旨在探究早期营养经历是否会对成年个体的TE产生长期影响。本研究选用实验小鼠的全同胞同窝幼崽，待其发育至成年后，通过整夜禁食的方式诱发蛰伏。我们以出生至成年阶段的体重作为营养状况的衡量指标，并计算相对体重（Relative Body Weight, RBW）以反映同窝个体间的营养状态差异。个体成熟后，我们对小鼠开展了5次重复的蛰伏诱导实验，每次实验包含24小时禁食与5天的恢复期。半数雌性小鼠的TE存在显著个体差异，而雄性小鼠则极少表现出日常蛰伏。对于雌性小鼠而言，出生时的RBW会对其成年后的TE产生影响，且该效应不受成年体重的干扰——即出生时RBW较低的雌性小鼠，成年后会表现出更高的TE水平。综上，本研究证实小鼠的TE存在同窝个体间差异，且该差异与胎儿期异质性的营养经历密切相关。