Tarantulas can produce silk from spigots on their feet as well as from their abdominal spinnerets, a finding that could help explain why spiders began to spin silk in the first place, researchers said on Wednesday.
The foot silk appears to help keep the spiders from sliding on slippery surfaces, Adam Summers of the University of California at Irvine and colleagues reported.
”If we find that other spiders in addition to these tarantulas have the ability to secrete silk from their feet, this could represent a major change in our evolutionary hypothesis regarding spider silk,” Summers said in a statement.
”It could mean that silk production actually originated in the feet to increase traction, with the diversity of spinneret silk evolving later.”
The spinneret is the organ in a spider that produces the thread for webs.
Summers, Stanislav Gorb of Germany’s Max-Planck-Institut and colleagues were studying zebra tarantulas from Costa Rica. Writing in the journal Nature, they said they were making the furry, striped spiders walk on vertical plates of glass to see how they used hairs and small claws on their feet to cling.
When the spiders started to slip, the researchers were surprised to see them start to produce fluid from their feet. It was silk.
Summers’ team used scanning electron microscopy to examine the spiders’ legs and found openings that resemble the spigots on the spinnerets in the abdomens of the spiders.
”Investigation of the genes involved in tarsal [foot] silk production should resolve whether the original function of spider silk was to increase traction or whether it was later co-opted for that purpose,” they wrote. – Reuters