German researchers have discovered that tarantulas secrete a silk-like substance from their feet to cling to smooth surfaces, adding a third known gripping method to the two already documented in spiders.
Scientists at the Max Planck Institute for Metals Research in Stuttgart conducted experiments with zebra tarantulas (Aphonopelma seemanni) from Costa Rica, guiding the spiders across a slick vertical glass pane. When descending, the animals released microscopic fibers, between 0.2 and 1.0 micrometres in diameter, from all four pairs of legs. The filaments stuck to the glass and prevented the spiders from slipping.
Spiders were already known to grip surfaces through thousands of tiny hairs that exploit weak van der Waals electrical forces, and through small claws that catch on rough textures. The newly identified mechanism involves nozzle-like structures on the feet that exude a viscous, silk-type material.
Team leader Stanislav Gorb of the institute's Evolutionary Biomaterials Group suggested spiders may have originally produced silk from their feet before evolving the abdominal spinneret used for webs. Researchers plan a genetic comparison of foot-silk proteins with spinneret-silk proteins. The findings were published in the 28 September 2006 issue of Nature.
Historical summary. TurkishPress restated this wire report, first published in September 2006, in its own words.