Last updated May 17, 2018 at 12:02 pm
Training spiders to jump on demand to discover secrets of animal movement.
In what sounds like the beginning of a horror film, scientists have successfully trained a spider to jump different distances and heights for the first time.
But rather than being the first step to building a spider army to take over the world, there is a more mundane purpose behind it. They have instead answered the question of why jumping spider anatomy and behaviour evolved the way it did.
This knowledge can then be used to develop a new class of agile micro-robots that are currently unthinkable using today’s engineering technologies (to then take over the world, no doubt).
A spider which will out jump you
Jumping spiders are extraordinary creatures. They can leap up to six times their body length from a standing start – way better than a human which is stretching at 1.5 times our body length.
In addition, the forces in their legs are immense, with up to 5 times their body weight during push off.
These prodigal jumping abilities make them ideal physical specimens to study the mechanics of leg movement, which could translate into more able exoskeletons and robots in our future.
In the most advanced study of spider movement, the team from the University of Manchester used 3D CT scanning and high-speed, high-resolution cameras to record, monitor and analyse a spider’s movement and behaviour as it jumped from platform to platform.
However, in order to analyse the jump properly, they needed the spider to jump on command. Which is why they trained a ‘Regal Jumping Spider (Phidippus regius) named Kim to make jumps from platforms at different heights and distances.
The biomechanics of a jump
The results show that Kim used different jumping strategies depending on the jumping challenge she was faced with.
To jump a short distance Kim went with a faster, lower trajectory which used up more energy, but minimises flight time. This makes the jump more accurate and more effective for capturing prey.
But when faced with a long distance jump, or a jump to a higher platform (like she would make to traverse rough terrain), Kim changed to the most efficient way of jumping to reduce the amount of energy used.
Prior to jumping, Kim was also seen to attached a silk safety line to the platform, assumed to be a backup should the jump go wrong. It’s also thought the line could help stability in the air.
Despite this high-detail analysis though, there are some questions still unanswered such as how she generates the power in her legs. Spiders use internal hydraulic pressure to extend their legs, essentially like a hydraulic ram. But despite knowing this for 50 years, we still didn’t know whether this hydraulic pressure is actively used to enhance or replace muscle force when the spiders jump.
The researchers found that, in the case of Kim, her estimated muscle strength alone would be sufficient to make the leap.
“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,” said Bill Crowther from the University of Manchester.
“Thus, the role of hydraulic movement in spiders remains an open question.”
The research has been published in Scientific Reports