![]() ![]() Moore and Jones say this predawn engineering feat could help the spiders avoid predators, providing perhaps an evolutionary explanation for the trashliners’ faster internal clocks. But thanks to their faster clocks, the trashliners get an early start, becoming most active while it’s still dark out. Most orb weaver species rebuild their webs just after sunrise. For a few hours every night, the spiders go to work building and repairing their webs. There, they wait for an unsuspecting insect to get caught, while remaining hidden from other predators themselves. For most of the day they hang out in their webs camouflaged within a vertical thread made out of trash (poop, leftover pieces of prey or other stray debris). The trashline orb weavers appear to get by just fine. Animals with gene mutations that significantly alter their circadian rhythms have shorter life spans, and circadian rhythm sleep disorders in humans can have profoundly negative effects, including increased risk for obesity, depression, cardiovascular disease and cancer. Having an internal clock that deviates from the natural 24-hour cycle is generally considered disadvantageous. Moore says that when he tells other circadian rhythm researchers about the finding, “Their first response is, ‘What?’ The second response is, ‘Oh shit!’” This process of shifting an internal clock to match external cues is called entrainment, and no other organism (that we know of) is able to shift its clock by more than an hour or two. For most of the animal world, that’s like having a six-hour jet lag every day, but the spiders instantly adjusted without any problems. If the researchers exposed the spiders to bursts of light, however, they would reset their clocks by six hours the next day. Without cues from light and heat to mark time passing, the spiders rested and moved in 18.5-hour cycles. Most of the time the spiders stayed motionless as if they were hanging out in their webs, but for a couple hours every day they exhibited bursts of activity. Whenever the arthropods moved, they triggered the beams to record their activity. ![]() To measure the clocks, the scientists put the spiders in test tubes, kept them in the dark and shined infrared beams on them. He says those animals, however, “have many difficulties and struggle to exist.” “Theoretically, should not exist.” The spiders are comparable to mutant animals scientists create in the lab to study circadian rhythms this short. We didn’t expect to see anything like this,” Moore said during a presentation at the annual Society for Neuroscience conference in Washington, D.C., last week. When the scientists measured the internal clocks of trashline orb weavers, however, they saw something extraordinary: The spiders ran on an 18.5-hour day, the shortest natural circadian cycle ever observed. Every organism previously studied-from humans to hamsters to fruit flies to bacteria-more or less follow the 24-hour day/night cycle. He asked Moore, a circadian rhythm expert, to look at the spiders’ internal clocks that regulate their daily activities.Ĭircadian rhythms dictate many of the body’s most fundamental processes, including eating, sleeping and hormone secretion. Jones noticed the spiders’ behavior-alternating between boldness and timidity-were also tightly linked to the time of day. Their aggression and passivity fluctuate depending on hormone levels that determine whether they are more likely to eat or be eaten. ![]() Jones studies social behavior in the orb weaver spiders that his undergraduate students collect near their East Tennessee State University campus. But a few years ago, his colleague Thomas Jones asked for his opinion about some weird spider behavior. Darrell Moore is typically a honeybee guy. ![]()
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