Silk Seat Belt
Sometimes people want to climb the walls - but if you're not a free climber, you should use a rope to be on the safe side. Tarantulas use the same bag of tricks to prevent unintentional slipping on slippery ground: similar to Homo sapiens, they tie themselves up - but with their feet.
Street canyons, skyscrapers, ground that suddenly gives way - none of this is an obstacle for Spider-Man. Peter Parker, aka Tobey Maguire, easily shakes his cobwebs out of his sleeve, swings through the air on his own sticky lasso, catches villains in the web and, dangling head under, gets his first kiss from his adored Mary Jane. Thank Hollywood cinema.
It is not known whether the inventor of the comic series on which the film is based knew Aphonopelma seemann, but it is not impossible - the Central American tarantula with the decorative stripes can certainly be found in the terrariums of spider lovers. And as every spider owner knows, vertical glass doors are no problem for the eight-legged friends: when digging, they sometimes push open the pane of the dwelling if it is not properly secured. The countless fine hairs on their toes act like a dry glue, based on van der Waals forces. This allows the animals to cling to smooth, sloping ground. If it gets a bit rough, little claws help out. The main thing is that the hold is secured.
But for how long? Stanislav Gorb from the Max Planck Institute for Metals Research and Senta Niederegger, now at the University of Jena, ordered their laboratory tarantulas to sit on a vertical glass wall under video surveillance. And the animals just sat and sat – the Van der Waals forces otherwise considered responsible would hardly have been enough.
But something caught the researchers' eyes: The spiders left footprints in the form of dozens of threads that were 0.2 to 1 micrometer thick and up to 2.5 millimeters long. However, the fibers did not come from the spinning glands - but from tiny gland-like structures on their feet.
As soon as the eight-legged creatures started to slide, they pressed the sections of their feet that showed the newly discovered tarsi silk to the glass. In doing so, they even moved the adjoining, densely hairy areas away from the ground: they thus renounced the van der Waals attraction. The Fuse Spider Silk is initially dispensed as a liquid drop, which then hardens on the surface much like regular glue. However, the fact that it is actually silk and not glue was recognized by the scientists from electron microscopic images that showed crossing fibers.
So far, scientists don't know if other spiders also shed silk on their legs. In any case, the discovery raises evolutionary questions: Is it an original ability and the glands on the abdomen developed later? Or was it just the tarantulas, which include the largest species, that developed this safety mechanism afterwards to prevent catastrophic falls? Perhaps a look at the responsible genes can bring more clarity. In return, the animals can stay on the ground.