Secrets of spider's jump unlocked thanks to cutting-edge facility

Supplementary content information

An Engineering and Physical Sciences Research Council (EPSRC)-funded facility has helped researchers to discover how spiders jump to catch their prey, a discovery which could help to inform the design of a new class of agile, micro-robots.

The team at The University of Manchester used 3D Computerised Tomography (CT) scanning at the EPSRC-supported Manchester X-ray Imaging Facility and high-speed, high-resolution cameras to record, monitor and analyse a spider’s movement and behaviour.

Their research has provided valuable new insights into why jumping spider anatomy and behaviour has evolved in the way it has, and has been covered by a wide range of media organisations.

Co-investigator Dr Russell Garwood said: “For this study, we used the facility to get a CT scan of the spider, which we used to find out where the centre of mass was.

“Being able to use facilities such as this is incredibly valuable; this is just one of several projects we have used the Manchester X-ray Imaging Facility for.”

Dr Mostafa Nabawy, lead author of the study, says: “The focus of the present 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 researchers 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 team then recorded the jumps using ultra-high-speed cameras, and used high resolution micro CT scans to create a 3D model of Kim’s legs and body structure in unprecedented detail.

CT scans utilised computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional (tomographic) images.

The results show 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 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, explains: “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.”

Reference: PN 28-18