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?
Author - Catie Lichten
First posted on 1st June, 2011 - but no less relevant today ! !
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