This Spider Runs on an 18.5-Hour Day and Shrugs Off Jet Lag Instantly

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Every organism ever studied — from humans to fruit flies to bacteria — runs its biological clock on a cycle close to 24 hours. Scientists studying the trashline orb weaver spider therefore got a profound shock when they discovered the creature operates on a mere 18.5-hour internal day, shorter than anything previously observed in nature. Circadian rhythm researcher Darrell Moore at East Tennessee State University describes the spiders as theoretically impossible to exist in their current form. When tested in complete darkness with no external time cues, the spiders rested and moved in 18.5-hour cycles. More remarkable still, a single burst of light could reset their internal clock by a full six hours with no apparent disruption — an adjustment that causes debilitating jet lag in virtually every other studied animal. Most organisms can shift their clocks by at most one or two hours. The team went on to test 20 species of spiders and found seven additional species running on clocks ranging from 17 to 29 hours, and some with no measurable clock at all. The discovery suggests the assumption that all animals operate near a 24-hour rhythm needs to be fundamentally re-examined.