Abstract：
Environmental gradients cause evolutionary and developmental changes in the cellular composition of organisms, but the physiological consequences of these effects are not well understood. Here, we studied experimental populations of Drosophila melanogaster that had evolved in one of three selective regimes: constant 16 °C, constant 25 °C, or intergenerational shifts between 16 °C and 25 °C. Genotypes from each population were reared at three developmental temperatures (16 °C, 20.5 °C, and 25 °C). As adults, we measured thorax length and cell sizes in the Malpighian tubules and wing epithelia of flies from each combination of evolutionary and developmental temperatures. We also exposed flies from these treatments to a short period of nearly complete oxygen deprivation to measure hypoxia tolerance. For genotypes from any selective regime, development at a higher temperature resulted in smaller flies with smaller cells, regardless of the tissue. At every developmental temperature, genotypes from the warm selective regime had smaller bodies and smaller wing cells but had larger tubule cells than did genotypes from the cold selective regime. Genotypes from the fluctuating selective regime were similar in size to those from the cold selective regime, but their cells of either tissue were the smallest among the three regimes. Evolutionary and developmental treatments interactively affected a fly\'s sensitivity to short-term paralyzing hypoxia. Genotypes from the cold selective regime were less sensitive to hypoxia after developing at a higher temperature. Genotypes from the other selective regimes were more sensitive to hypoxia after developing at a higher temperature. Our results show that thermal conditions can trigger evolutionary and developmental shifts in cell size, coupled with changes in body size and hypoxia tolerance. These patterns suggest links between the cellular composition of the body, levels of hypoxia within cells, and the energetic cost of tissue maintenance. However, the patterns can be only partially explained by existing theories about the role of cell size in tissue oxygenation and metabolic performance.
摘要：
环境梯度引起生物体细胞组成的进化和发育变化，但是这些影响的生理后果还没有得到很好的理解。这里,我们研究了果蝇的实验种群，这些果蝇在三种选择性方案之一中进化：恒定的16°C，恒定25°C,或在16°C和25°C之间的代际变化。每个种群的基因型在三个发育温度（16°C，20.5°C,和25°C）。作为成年人,我们从进化和发育温度的每种组合中测量了果蝇的Malpighian小管和翼上皮的胸部长度和细胞大小。我们还将来自这些治疗的果蝇暴露于几乎完全缺氧的短时间内，以测量缺氧耐受性。对于来自任何选择性制度的基因型，在较高温度下的发育导致具有较小细胞的较小果蝇，不管组织。在每个发育温度下，与冷选择方案的基因型相比，热选择方案的基因型具有较小的身体和较小的翼细胞，但具有较大的小管细胞。波动选择方案的基因型与冷选择方案的基因型相似，但是它们的任何一个组织的细胞都是三种体系中最小的。进化和发育治疗相互作用地影响了苍蝇对短期麻痹性缺氧的敏感性。在较高温度下发育后，来自冷选择方案的基因型对缺氧的敏感性较低。来自其他选择性方案的基因型在较高温度下发育后对缺氧更敏感。我们的结果表明，热条件可以触发细胞大小的进化和发育变化，再加上身体大小和缺氧耐受性的变化。这些模式表明了身体细胞组成之间的联系，细胞内的缺氧水平，和组织维护的能量成本。然而,关于细胞大小在组织氧合和代谢表现中的作用的现有理论只能部分解释这些模式。
