Dung beetles show metabolic plasticity as pupae and smaller adult body size in response to increased temperature mean and variance
Dung beetles show metabolic plasticity as pupae and smaller adult body size in response to increased temperature mean and variance
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DOI：
10.1016/j.jinsphys.2021.104215
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发表时间：
2021-03-12
影响因子：
2.2
通讯作者：
Sheldon, Kimberly S.
中科院分区：
文献类型：
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作者：
Fleming, J. Morgan;Carter, Amanda W.;Sheldon, Kimberly S.
尽管生物体可能会利用热塑性来应对新的温度状态，但我们对塑料反应的理解是有限的。传统上，热塑性研究的重点是生物体对平均温度变化的反应。然而，与平均温度相比，温度变化的增加对生物体性能的影响更大。此外，热塑性研究通常是为了研究在更极端的温度下的可塑性，尽管生物体对它们经历的每日温度波动进行生理调整。以金牛天牛(Onthphagus Taurus)的蛹为研究对象，研究了在物种临界温度极限范围内的温度条件下，温度均值和温度变化对可塑性的影响。我们在九种孵化处理之一下饲养了40只甲虫，从卵到蛹(n=20)或成虫(n=20)，包括三个平均温度(22，24，26摄氏度)和三个波动幅度(+/-2，+/-4，+/-8摄氏度)的所有组合。为了测量蛹的热塑性，我们量化了每次处理20只甲虫在不同温度范围(即15、20、25和30摄氏度)下产生的二氧化碳。二氧化碳产生量和温度之间的关系提供了在给定温度(即使用截距)和热敏感性(即使用斜率)下的能量成本估计。我们在每个处理中饲养剩余的金牛座(n=20)到成年，然后记录体重(G)以确定身体大小，这是健康的替代指标。在温度均值和方差的加性效应和交互作用下，蚕蛹表现出热塑性。与所有其他处理相比，在最温暖和最多变的处理(26+/-8摄氏度)饲养的幼虫显示出总体新陈代谢的最大降幅，而且这种处理(26+/-8摄氏度)的成虫也比任何其他处理的成虫小得多。我们发现，温度的平均值和方差都对蛹的热塑性有贡献，并对成虫的体型有影响，这一性状与屎甲虫的适合性有关。重要的是，我们在治疗中使用的温度并不极端，很可能远远低于该物种的临界最高温度，这表明生物体可以对它们在白天或季节性时间尺度上经历的温度进行调整。
Though organisms may use thermal plasticity to cope with novel temperature regimes, our understanding of plastic responses is limited. Research on thermal plasticity has traditionally focused on the response of organisms to shifts in mean temperatures. However, increased temperature variation can have a greater impact on organismal performance than mean temperature alone. In addition, thermal plasticity studies are often designed to investigate plasticity in response to more extreme temperatures despite the fact that organisms make physiological adjustments to diurnal temperature fluctuations that they experience. Using pupae of the dung beetle Onthophagus taurus, we investigated the potential for plasticity in response to increasing temperature mean and variance using thermal regimes that were well within the species critical thermal limits. We reared 40 beetles from egg to pupae (n = 20) or adults (n = 20) at one of nine incubation treatments, including all combinations of three mean temperatures (22, 24, 26 degrees C) and three amplitudes of fluctuation (+/- 2, +/- 4, +/- 8 degrees C). To measure thermal plasticity of pupae, we quantified CO2 production across a range of temperatures (i.e., 15, 20, 25, and 30 degrees C) for 20 beetles per treatment. The relationship between CO2 production and temperature provides an estimate of energetic costs at a given temperature (i.e., using the intercept) and thermal sensitivity (i.e., using the slope). We reared the remaining O. taurus in each treatment (n = 20) to adulthood and then recorded mass (g) to determine body size, a proxy for fitness. Pupae exhibited thermal plasticity in response to the additive and interactive effects of temperature mean and variance. Pupae reared in the warmest and most variable treatment (26 +/- 8 degrees C) showed the greatest decrease in overall metabolism compared to all other treatments, and adult beetles from this treatment (26 +/- 8 degrees C) were also significantly smaller than adult beetles from any other treatment. We found that both temperature mean and variance contributed to thermal plasticity of pupae and had consequences for adult body size, a trait related to dung beetle fitness. Importantly, the temperatures we used in our treatments are not extreme and are likely well below the critical thermal maxima of the species, demonstrating that organisms can make adjustments to temperatures they experience across diurnal or seasonal timescales.