While reducing the investment in the visual system of nocturnal/cave-dwelling species appears to be an evolutionarily stable strategy in response to the difficulty of locating food in the dark, relying on visual information for diurnal species is crucial for their survival and reproduction. However, the manner in which species evolve and adapt to the energetic demands placed upon them by environmental changes is not perfectly understood. In particular, if life in the dark is associated with a reduction in energetic demand, would relocation to a well-lit environment increase energetic demand? This question has a bearing upon our understanding of factors that influence the ability of species to adapt to new habitats. After observing that a sub-population of "Dark-flies" (i.e., fruit flies bred in the dark for more than 60 years) has been selected with a larger visual system (optic lobes) and brain over the course of being maintained in normal lighting conditions for 3 years (DFLight), we used the CAFÉ assay method to investigate the differences in the two strains' energetic demands in the present study. We therefore measured brain size, body size, and food consumption in Dark-flies, DFLight, and Oregon flies (i.e., the fly species most genetically similar to Dark-flies). We found that the DFLight consumed more food solution than the Dark-flies, which correlates with that strain's larger brain size and improved visual capability compared to the Dark-flies. In addition, and although the -Oregon flies initially consumed less food solution than the DFLight, the amount consumed by these two strains by the end of the CAFÉ assay was approximately the same. This suggests that the Dark-flies have adapted their metabolism or feeding strategies in response to a dark environment. Our investigation therefore provides empirical evidence elucidating the manner in which energetic demands change in response to environmental changes and the cross-generational effect upon sensory-system investment.

中文翻译：

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光照对黑蝇（果蝇）的食物消耗和大脑大小的影响。

减少夜间/洞穴栖所物种视觉系统的投资似乎是一种进化上稳定的策略，以应对在黑暗中寻找食物的困难，而依靠视觉信息获取昼夜物种对于它们的生存和繁殖至关重要。但是，人们对物种进化并适应环境变化对它们的精力旺盛的需求的方式的了解还不够。尤其是，如果黑暗中的生活与能量需求的减少有关，搬迁到光线充足的环境中会增加能量需求吗？这个问题与我们对影响物种适应新生境能力的因素的理解有关。观察到“黑蝇”的子种群（即，在黑暗中繁殖超过60年的果蝇）在正常光照条件下保持3年（DFLight）的过程中，已选择具有较大的视觉系统（光叶）和大脑的果蝇，我们使用了CAFÉ分析法研究本研究中两种菌株的能量需求差异。因此，我们测量了黑蝇，DFLight和俄勒冈蝇（即，遗传上与黑蝇最相似的蝇种）的大脑大小，体重和食物消耗。我们发现DFLight比暗蝇消耗的食物更多，这与黑蝇相比该菌株更大的大脑尺寸和改善的视觉能力有关。此外，尽管-俄勒冈州果蝇最初消耗的食物溶液少于DFLight，到CAFÉ分析结束时，这两种菌株的消耗量大致相同。这表明，黑蝇已经适应了黑暗环境，适应了新陈代谢或摄食策略。因此，我们的研究提供了经验证据，阐明了能量需求随环境变化而变化的方式以及对感官系统投资的跨代影响。