Spiders Get a Grip

It seems Spider-Man was right all along.

Biologists always believed that spiders produce silk only from organs on their abdomens, called spinnerets. But, for decades, Spider-Man has been swinging on draglines spun from web-shooters near his hands. Now, new research shows that's what some spiders do, too.

Two features enable spiders to cling upsidedown or to vertical surfaces: tiny foot-claws that dig into the surface, and tiny foot-hairs that create a sort of static-electricity bond between their feet and whatever they're climbing.

Recently, while watching zebra tarantulas walk on a sheet of smooth glass, scientists discovered a third, Spidey-like tool.

When researchers tilted the glass vertically, the heavy tarantulas slid down the smooth surface a bit, but then halted their slide. A close look showed threads of sticky silk coming from each foot. A closer look showed tiny silk-spigots, similar to those in the abdominal spinnerets that make silk for webs and nests.

The discovery raises new questions about spider silk. Was it originally used to help spiders move around and later adapted for capturing prey? And do all spiders spin foot-silk, or just heavy species like tarantulas?

Maybe scientists should just ask Spider-Man.

-Mary Jo Hunst

Copyright Carus Publishing Company Apr 2007
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