Scientists unravel jumping strategies of spiders

In a study that could lead to new generation of micro-robots inspired by mature, scientists have unlocked the secrets of how some predatory spiders catch their prey while hunting by successfully training one to jump different distances and heights for the first time.

Researchers from the University of Manchester in Britain trained the spider, which they nicknamed Kim, to jump different heights and distances on a manmade platform in a laboratory environment.

Kim belongs to a species of jumping arachnid known as Phidippus regius, or 'Regal Jumping Spider'.

The findings, published in the journal Scientific Reports, showed that Kim can leap up to six times its body length from a standing start. The best a human can manage is about 1.5 body lengths.

"The force on the legs at take-off can be up to 5 times the weight of the spider - this is amazing and if we can understand these biomechanics we can apply them to other areas of research," said Mostafa Nabawy, lead author of the study.

The researchers used 3D CT scanning and high-speed, high-resolution cameras to record, monitor and analyse a spider's movement and behaviour.

The results showed that this particular species of spider uses different jumping strategies depending on the jumping challenge it is presented with.

For example, to jump shorter, close-range distances Kim favoured a faster, lower trajectory which uses up more energy, but minimises flight time. This makes the jump more accurate and more effective for capturing its prey.

But, if Kim is jumping a longer distance or to an elevated platform, perhaps to traverse rough terrain, she jumps in the most efficient way to reduce the amount of energy used.

Insects and spiders jump in a number of different ways, either using a spring like mechanism, direct muscle forces or using internal fluid pressure.

Scientists have known for more than 50 years that spiders use internal hydraulic pressure to extend their legs, but what is not known is if this hydraulic pressure is actively used to enhance or replace muscle force when the spiders jump.

"Our results suggest that whilst Kim can move her legs hydraulically, she does not need the additional power from hydraulics to achieve her extraordinary jumping performance. Thus, the role of hydraulic movement in spiders remains an open question," explained Bill Crowther, co-author of the study.

--IANS

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