Sunday, 26 May 2019

NATURE | British scientists discover secrets of animal movement by training spiders

LONDON, ENGLAND — Scientists at the University of Manchester revealed Tuesday how they have trained a spider to jump on demand to help them discover secrets of animal movement.

The study is the most advanced ever of its kind and first to use 3D CT scanning and high-speed, high-resolution cameras to record, monitor and analyze a spider’s movement and behavior. It will also help in the development of future robots.

The research has unlocked the secrets of how some predatory spiders catch their prey whilst hunting. They did this by successfully training for the first time a spider they called Kim to jump different distances and heights.

Kim was taught to jump on a manmade platform in a laboratory environment. She belongs to a species of jumping arachnid known as the Regal Jumping Spider.

The team recorded the jumps using ultra-high-speed cameras and high-resolution micro CT scans to create a 3D model of Kim’s legs and body structure in unprecedented detail.

The aim of the research is to answer the question of why jumping spider anatomy and behavior evolved the way it did. Secondly the project used the improved understanding of spiders to imagine a new class of agile micro-robots that are currently unthinkable using today’s engineering technologies.

Dr Mostafa Nabawy, lead author of the study, said: “The focus of the work is on the extraordinary jumping capability of these spiders. A jumping spider can leap up to six times its body length from a standing start. The best a human can achieve 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.”

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

To jump shorter, close-range distances Kim favored a faster, lower trajectory which uses up more energy, but minimizes 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 isn’t known is if this hydraulic pressure is actively used to enhance or replace muscle force when the spiders jump.

Dr Bill Crowther, co-author of the study, said: “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.

The study is being published in the journal Nature Scientific Reports.

Youtube video courtesy of the University of Manchester Media Relations

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