Researchers working at Macquarie University and in Germany and Argentina have found that an Australian spider species has a unique approach to web engineering which bypasses the usual trade-off between strength and elasticity.
Their insights into how the rufous net-casting spider (Asianopis subrufa) of eastern Australia skilfully spins its web and the detailed structure of the spider's silk may have application in high-tech synthetic fibres for safety, medical applications and even aviation.
Rather than weaving a static web to catch insects, net-casting spiders (Deinopidae) make a small, sticky net and ambush prey by using their front legs to cast the net at lightning speed.
Dream weaver: The rufous net-casting spider's uniquely stretchy web could have impactful real-world translations.
"Just by observing the spider's behaviour, we suspected something spectacular was going on," said Dr Martín Ramírez, of the Museum of Natural Sciences in Buenos Aires, Argentina, co-author of the study just published in the scientific journal PNAS.
Remarkably, research found the spider's net can expand by up to 150 per cent in some dimensions but then retracts and contains the prey securely as the spider retrieves it.
"The net is incredibly stretchy," said Dr Ramírez. "No normal spider silk can extend that far yet still return to its original form."
Rufous net-casting spiders were initially collected on Macquarie University's Wallumattagal campus in north suburban Sydney and at the nearby Bidjigal nature reserve, then studied in the lab using high-speed video (1000-1300 frames per second) and high-resolution scanning electron microscopy.
Microscopic analysis revealed a previously unknown "meta-structure": the central silk threads of the net are elastic, but the spider adds curly and crinkled threads that change the net's material properties.
Strong and stretchy: The unique meta-structure of a rufous net-casting spider's silk.
"We found that the prey-catching silk has a flexible, wool-like, winding structure that allows the spider to cast the net rapidly," explained lead study author Dr Jonas Wolff of the University of Greifswald, Germany, who is an Honorary Research Fellow in the School of Natural Sciences at Macquarie University.
"As soon as the fibres have been stretched, the microstructural loops straighten, giving the material much greater strength and preventing the thread from breaking under the strain of hauling in captured prey," said Dr Wolff, who spent several years at Macquarie University as a postdoctoral researcher.
Slow-motion videos helped researchers study the net-casting spider's reel-spinning technique, revealing how it moves its tiny spinnerets to mix fibre and create loops in different sections of its web to integrate both extensibility and load-bearing capacity.
Translation of these discoveries from spider silk research could open new avenues for innovation in materials science, the researchers suggest, offering the potential to develop high-tech fibres that are flexible and robust at the same time, overcoming the trade-off between stability and elasticity.
Dr Jonas Wolff leads the Evolutionary Biomechanics group, Zoological Institute and Museum, University of Greifswald, Germany, and is an Honorary Research Fellow, School of Natural Sciences, Faculty of Science and Engineering at Macquarie University.
