Animals match their biological rhythms to the day-night cycle thanks to their circadian clocks, which are usually kept on time using cues from light. But do organisms that live in perpetual darkness, such as the blind cavefish (Phreatichthys andruzzii; pictured), have such clocks? Cristiano Bertolucci at the University of Ferrara in Italy and his colleagues show that they do. However, the clock's oscillations are set by feeding times, not light, and cycle every 47 hours, rather than every 24.
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机译：得益于它们的生物钟，动物可以将它们的生物节律与昼夜周期相匹配，该生物钟通常利用光线的提示来保持准时。但是，生活在永久黑暗中的生物，例如盲目的洞穴鱼（Phreatichthys andruzzii；如图所示）是否有这种时钟？意大利费拉拉大学（University of Ferrara）的克里斯蒂亚诺·贝托鲁奇（Cristiano Bertolucci）和他的同事证明了他们的所作所为。但是，时钟的振荡是由供电时间（而不是光）设置的，并且每47小时而不是每24小时循环一次。
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