In addition to its many other amazing abilities, spider silk has seen the arachnids travel thousands of miles through the air like balloons. It has long been believed that this phenomenon was simply a case in which the wind picked it up, but a new study has found that the creatures actually use atmospheric electric fields instead.
At first glance, the wind theory seems like common sense, the spider balloon, but it does have a few holes. For one thing, the silk strands themselves form a fan shape that apparently is unable to catch enough air to lift the creatures. In addition, it has been observed that they also have good airtime on quiet days.
"Current theories can not predict Spidern's ballooning patterns when using wind alone as a driver," says Erica Morley, lead researcher in the study. "Why is it that on some days large numbers fly into the air, while on other days no spiders will try to balloon themselves? We wanted to find out if there are other external forces as well as aerodynamic resistances that could trigger balloon flights System could they use to detect this stimulus? "
An alternate idea that has been circulated (pun intended) is that spiders tap electrical fields (E-fields). These E-fields exist in all matter and even surround the Earth in the form of the atmospheric potential gradient (APG). But while insects like bees can spot them, spiders are not known.
Oddly enough, the Bristol researchers say that no one has ever tested whether e-fields play a role in spinning balloons or even recognize them. To find out, the team placed linyphid spiders in a lab environment free of external wind or natural e-fields. Then they created their own electric fields in space, with the same strength as in the atmosphere.
The team noticed that the spiders tiptoed in response to the E-fields, raising their bodies higher and pointing their belly up, suggesting that the creature was trying to balloon. The tiny hairs on the spider legs also stood in response to the E-field, which the team suspected had felt the load.
As the e-field became stronger, the spiders rose into the air and were lowered again as the scientists switched off the field. This shows that spiders can use electrostatic forces to lift off, and once they are in the air, they might plunge into the wind to travel long distances.
"So far it has been thought that this type of propagation of drag forces is caused by wind or thermal, but we show that electric fields in the atmosphere can trigger balloons and create buoyancy without air movement," says Morley. "This means that both electric fields and air resistance can provide the forces needed to propagate spiders in nature."
The team wants to investigate if other animals are discovering and using electric fields for similar behaviors.
The research was published in the journal Current biology, and the team describes the study in the video below.
Source: University of Bristol
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