Looking just outside into their gardens for a bit of inspiration, one group of Oxford University researchers has sought out to discover how common spider species spin such long, ornate fiber while only being a few nanometers thick. Hoping to reveal nature's secret, which may someday revolutionize the technological industry as manufacturers find new ways of commercially spinning nano-scale filaments, the researchers captured female Uloborus plumipes commonly known as "feather-legged lace weavers" and watched them spin their webs.
The new study published this week in the journal Biology Letters reveals a new method of spinning that researchers previously did not see in the wild. Instead of utilizing sticky glue on the threads to snare its prey, the lace weavers used a more archaic technique of dry-capturing their next meal. After spinning the nanothreads, the spiders then utilize specialized hairs on their hind legs to electrically "fluff" the filaments, and establish a form of static attraction that acts very similarly to glues found in traditional webs.
"Uloborus has unique cribellar glands, amongst the smallest silk glands of any spider, and it's these that yield the ultra-fine 'catching wool' of its prey capture thread" coauthor of the study and professor of Oxford University's Department of Zoology, Dr. Katrin Kronenberger says. "The raw material, silk dope, is funnelled through exceptionally narrow and long ducts into tiny spinning nozzles or spigots. Importantly, the silk seems to form only just before it emerges at the uniquely-shaped spigots of this spider."
To further investigate the extremely small nano-fibers the Oxford researchers photographed and utilized three microscopy techniques to capture the spiders' spinning in action. The "cribellum", an ancient spinning organ not commonly found in spiders today, was of particular interest to the researchers as they discovered that Uloborus had thousands of microsopic silk-producing units which funneled down to the diameter of only 50 nanometers.
The intricate fiber spinning, however, was only part of the lace weavers' charm. Researchers found that even once the filaments were spun, it was the spiders' combing behavior that actually gave the webs their sticky nature. And researchers hope to one day be able to mimic this "teasing" technique.
"The swathe of gossamer, made of thousands of filaments, emerging from these spigots is actively combed out by the spider onto the capture thread's core fibres using specialist hairs on its hind legs" the study's other coauthor, Professor Fritz Vollrath says. "This combing and hackling - violently pulling the thread - charges the fibres and the electrostatic interaction of this combination spinning process leads to regularly spaced, wool-like 'puffs' covering the capture threads. The extreme thinness of each filament, in addition to the charges applied during spinning, provides Van der Waals adhesion. And this makes these puffs immensely sticky."
