In natural populations, individuals experience daily fluctuations in environmental conditions that synchronise endogenous biorhythms. Artificial alterations of environmental fluctuations can have negative consequences for life history traits, including lifespan. In laboratory studies of aging, the role of fluctuating temperature is usually overlooked and we know little of how thermal fluctuation modulates senescence in vertebrates. In this longitudinal study we followed individually-housed turquoise killifish, Nothobranchius furzeri, from two thermal regimes; ecologically relevant diel fluctuations (20 °C - 35 °C) and stable temperature (27.5 °C), and compared their survival, growth and reproduction. Fish experiencing fluctuating temperatures had a longer median lifespan but reached smaller asymptotic body size. Within-treatment variation indicated that extended lifespan in fluctuating temperatures was not causally linked to decreased growth rate or smaller body size, but occurred solely due to the effect of thermal fluctuations. Male body size was positively associated with lifespan in stable temperatures but this relationship was disrupted in fluctuating thermal regimes. Females exposed to fluctuating temperatures effectively compensated egg production for their smaller size. Thus, there was no difference in absolute fecundity between thermal regimes and body-size corrected fecundity was higher in females in fluctuating temperatures. Overall, despite a brief exposure to sub-optimal thermal conditions during fluctuations, fluctuating temperature had a positive effect on survival and reproduction. These results suggest that the expression of life history traits and their associations under stable temperatures are a poor representation of the relationships obtained from ecologically relevant thermal fluctuations.

在自然种群中，个体每天都会经历与内源性生物节律同步的环境条件波动。人为改变环境波动会对生活史特征（包括寿命）产生负面影响。在衰老的实验室研究中，温度波动的作用通常被忽略，我们对热波动如何调节脊椎动物的衰老知之甚少。在这项纵向研究中，我们追踪了单独饲养的绿松石kill鱼Nothobranchius furzeri，来自两个热态；生态相关的狄尔波动（20°C-35°C）和稳定的温度（27.5°C），并比较它们的生存，生长和繁殖。温度波动的鱼的平均寿命更长，但渐近体形较小。处理内变化表明，温度波动的延长寿命与生长速度降低或体型较小没有因果关系，而仅仅是由于热波动的影响而发生的。男性的体型与稳定温度下的寿命呈正相关，但这种关系在温度波动的情况下被破坏。暴露在温度波动中的雌性由于体型较小而有效地补偿了产蛋量。从而，热疗方案之间的绝对生殖力没有差异，并且温度波动的女性体重校正后的生殖力更高。总体而言，尽管在波动过程中短暂暴露于次佳的热条件下，但温度波动对生存和繁殖有积极影响。这些结果表明，在稳定温度下生活史特征及其关联的表达不能很好地表示从生态学相关的热波动中获得的关系。