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Ig Nobel for slime networks

Pete Wilton

An experiment to test if slime moulds can design efficient railway networks has won a team, including Oxford University researchers, an Ig Nobel Prize.

We reported on the original research back in January, but I asked team-member Mark Fricker of Oxford University’s Department of Plant Sciences why scientists study these strange organisms, what they can teach us and how they take 'networking' to a whole new level:

OxSciBlog: What makes slime moulds so interesting to study?
Mark Fricker: The acellular slime molds represent a very unusual life form. The whole organism is one single giant cell, albeit containing many nuclei, that can grow to be many centimeters in size. In the wild, it spreads as a pulsing network seeking out food sources such as bacteria, fungi or dead insects that it engulfs and then digests.

Even with a low power microscope or a hand lens it is possible to watch the shuttle flow of cytoplasm coursing through the system that somehow manages to resolve into an efficient transport network. Although it has no brain or nervous system, its exploratory behaviour and the network itself is highly responsive and continuously adapts to whatever is happening around it.

It's a great system to then challenge with different stimuli to see how it reacts. If things get really bad, it simply dries out and waits until things get better or forms spores that can spread to other sites.

OSB: Why is it useful to compare their networks with manmade ones?
MF: We already know that the slime mold is capable of solving certain abstract problems, such as the shortest path through a maze or finding the most efficient way to connect geometric arrangements of different food sources using Steiner points, that is computationally difficult to achieve.

However, we wanted some way to determine whether understanding such behaviour could have utility beyond simple fascination with such elegant biology. Providing a real-world test problem that we already know the answer to seemed to be one way to discover whether the lessons we might learn from the slime mold could have applications elsewhere.

OSB: What can we learn from how slime moulds build networks?
MF: As there is no obvious distinct communication system within the organism, we infer that the network is able to form and adapt based solely on local information. The overall behaviour emerges from the collective interaction of the constituent parts.

Control by such a decentralised system is in marked contrast to management through a central control centre that has to assimilate all the necessary information, processes it and then send out instructions to achieve a co-ordinated response. We also infer that the lack of a "brain" means the rules governing local behaviour are likely to be simple, but iteratively give rise to apparently sophisticated problem-solving behaviour, very similar in principle to the way that complex behaviour can emerge in social insects such as termites or bees.

Decentralised control systems running with simple rules offer attractive possibilities to establish readily scalable, low maintenance, robust and adaptable network architectures. Equally, we have to be careful in pushing these analogies very far as, although the slime mold networks match the infrastructure networks at one level, they develop using very different processes that would be completely impractical to replicate in all but a limited number of real-world scenarios.

Nevertheless, there may be interesting general concepts that emerge such as communication of fuzzy information over long distances and information through conservation laws that are intrinsically associated with physical flows. It is also interesting that many systems in biology show oscillatory behaviour that may assist in co-ordination of behaviour, whilst most man-made control strategies deliberately try to suppress such phenomena.

OSB: How did you feel when you heard you’d won an Ig Nobel?
MF: Great. I think they are a wonderful vehicle to make science accessible and entertaining.

OSB: What do you hope to investigate next as part of this research?
MF: We have a number of different organisms, including fungal mycelia, that also produce elegant networks that appear to be tuned to a different balance between cost, efficiency, resilience and control complexity.

They also form their networks by completely different methods to slime molds at the molecular level, yet there are already interesting similarities including the conservation flows and pulsating behaviour at a macroscopic level. This again hints at some universal principles that govern this type of network formation that can be achieved with a wide variety of different components. This is also important as it suggests that the control principles can also be transferred to non-biological systems as well.

Unravelling these processes and modelling the critical components needs creative links between biologists, physicists, mathematicians and engineers. This network of network people is what we are currently building.

Mark Fricker and colleagues won this year's Transportation Planning Prize.