By studying spider limb regeneration, scientists have been able to investigate the rules that spiders use to construct their webs and embed them into virtual spiders to be used to inform aspects of modern robotics.
Spider webs are engineering wonders, built by species with 400 million years of accumulated practices and there is much to be learnt from the construction of these webs and the functionality of the creatures that make them.
Garden cross spiders can regenerate lost legs and use them immediately to build perfect webs, despite the new limb being much shorter than the one it replaced. This fascinating phenomenon has allowed scientists to investigate the rules spiders use to build their webs and how they use their legs for measurements.
Studies at the Universities of Oxford and Aarhus have revealed how a spider’s regenerated leg movements fit in with the other legs that are of normal length, coordinating complex movements and thread manipulations.
A study published by Fritz Vollrath and Thiemo Krink shows that each limb acts like a semi-independent computer and does much of the calculations for its positioning locally through adapted sensors, a phenomenon called morphological computing.
The complex sequences of movements and manipulations that the spider uses to construct its web can be translated into decision rules that can be tested. The behaviour is encoded in a set of formal ruled embedded in a virtual spider that draws computer webs on computer screens.
By using a using a combination of experiments with both real and virtual spiders, scientists have been able to analyse and verify the rule sets. They then encoded the decision rules into virtual genes and used a computer amination process – Genetic Algorithm – to develop computer-based ecosystems where different virtual challenges can be tested by virtual spiders.
Professor Fritz Vollrath, from the Oxford Department of Zoology and lead author, said: “We were surprised that an animal was able to ‘do its thing’ perfectly with a leg that is half its normal length and totally new i.e. with muscles that have not exercised and sensors that had no time to ‘learn’ how to respond.
“It has been exciting to use our novel techniques to unravel an animal’s hidden rules of behaviour by combining computer modelling with experimental studies of real animals’ behaviours.
“Encoding the spider’s decision rules into cyber genes allows us to let the system evolve in a computer-based ecosystem by responding to virtual challenges such as cyber flies and imagined cost-benefit balances.”
Vollrath and Krink hope that this understanding will inform aspects of modern Robotics about the ways and means that animals can execute complex tasks using simple rules in combination with adaptable skins and skills.
The algorithms used by virtual spiders are embedded in applications that can be downloaded, allowing students to study the decision rules online, and explore the role of evolution in animal behaviour and ecology.
The researchers aim to forge deeper links with roboticists to explore how spider behaviour can inform unmanned vehicle piloting and navigation, and how novel robots could be constructed and operate.