The secret is finally out about how the hairy giants of the arachnid world hang on to vertical slopes. Researchers have discovered that tarantulas can, like Spiderman, shoot silk from tiny ‘spigots’ on their feet. The findings, recently published by Claire Rind and colleagues at Newcastle University, appear in the Journal of Experimental Biology.
Most spiders handle steep climbs effortlessly thanks to thousands of tiny hairs on their feet, which use molecular forces of attraction to grip even the smoothest surfaces. Tarantulas, however, can weigh over 50g and are too heavy to rely on these hairs alone when climbing. For scientists, it was unclear how the spiders avoid dangerous falls off of steep inclines.
The authors of a study in 2006 found that tarantulas placed on an inclined platform left behind silk footprints. They proposed that the animals might be clinging to the platform by releasing silk from their feet. But another explanation was that the spiders’ feet simply collect silk from rubbing against the silk-producing organs in their abdomens.
Rind’s team solved the puzzle by repeating the test and looking at the tarantula’s anatomy. They too found silk footprints on the platform, but only if they had shaken it enough to make the tarantula slip, suggesting the spider only releases silk when necessary. To locate the silk’s source, they examined spiders’ moulted skin. With electron microscopy, they found taller, nozzle-like structures amid the hairs on the feet, some of which actually had strands of silk emerging from their tips. The observations confirmed that tarantulas can release silk from their feet and the new structures were identified as the silk spigots.
According to Rind, the new findings may fill in gaps in our understanding of how modern silk-spinning spiders evolved. They also make us wonder, which superhero powers will appear in nature next?
Posted on Wednesday, 1st June, 2011