Specialized Leg Organs Help Spiders Glean Information From Their Silk

Brett Smith for redOrbit.com – Your Universe Online
A spider’s web is more than just a home or trap for unsuspecting prey, it’s also a communications network capable of telling a spider information about prey, mates, and its own structural integrity.
According to a new report in the journal Advanced Materials, spider silk can be tuned to a wide range of harmonics and these various frequencies provide a wealth of information to spiders, which sense the frequencies using leg organs called slit sensillae.
“Most spiders have poor eyesight and rely almost exclusively on the vibration of the silk in their web for sensory information,” said study author Beth Mortimer, a biologist at the Oxford Silk Group at Oxford University. “The sound of silk can tell them what type of meal is entangled in their net and about the intentions and quality of a prospective mate. By plucking the silk like a guitar string and listening to the ‘echoes’ the spider can also assess the condition of its web.”
This aspect is utilized by the spider through the “tuning” of silk to pick up sensory information. To examine the sonic qualities of silk, the scientists used ultra-high-speed cameras to capture the threads as they reacted to the impact of bullets. Specialized lasers were used to pick up the silk’s smallest vibrations.
“The fact that spiders can receive these nanometer vibrations with organs on each of their legs, called slit sensillae, really exemplifies the impact of our research about silk properties found in our study,” said study author Shira Gordon, a researcher at the University of Strathclyde.
“These findings further demonstrate the outstanding properties of many spider silks that are able to combine exceptional toughness with the ability to transfer delicate information,” added study author Fritz Vollrath, an ecology professor in the Oxford Silk Group. “These are traits that would be very useful in light-weight engineering and might lead to novel, built-in ‘intelligent’ sensors and actuators.”
“Spider silks are well known for their impressive mechanical properties, but the vibrational properties have been relatively overlooked and now we find that they are also an awesome communication tool,” said Chris Holland, a research fellow at the University of Sheffield. “Yet again spiders continue to impress us in more ways than we can imagine.”
“’It may even be that spiders set out to make a web that ‘sounds right’ as its sonic properties are intimately related to factors such as strength and flexibility,” Mortimer said.
Spider silk has inspired researchers for years and a team from the University of Akron revealed in May that it had developed a more efficient and stronger commercial and biomedical adhesive inspired by the material.
According to a report in the Journal of Polymer Physics, the researchers used a process called electrospinning to draw very fine fibers from liquid polyurethane using electrical charges. This allowed them to imitate the efficient staple-pin design by pinning down a nylon thread with the electrospun fibers.
“This adhesive architecture holds promise for potential applications in the area of adhesion science, particularly in the field of biomedicine where the cost of the materials is a significant constraint,” the study authors wrote.

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