Australian scientists are using a humble indigenous freshwater crayfish, known as the Yabby, as their inspiration to help build miniature robots for NASA’s exploration of Mars.

Platoons of robo-yabbies could soon explore the red planet searching for water or conducting chemical analysis of the atmosphere and the planet’s crust – tasks that are currently impractical for humans.

University of Melbourne zoologist, Professor David Macmillan and associates in his Melbourne laboratory and collaborating laboratories overseas are using the Yabby (Cherax destructor) to help advance research in the global movement called biomimetics. The movement is a rapidly expanding area of research that harvests nature’s best design ideas for use in robotics.

“Invertebrates such as insects and crustaceans achieve similar movement and sensory outcomes to humans. For example, finding food and selection of appropriate mates and nesting sites. Where humans use millions of neurons to achieve such outcomes, invertebrates do it with thousands. Where humans use hundreds, invertebrates may use as few as six,” he says.

“It is this parsimony, that ability to control complex behaviours with an amazingly small amount of brain power that attracts scientists from disciplines including robotics engineering, computer programming, biology, mathematics and neurology.”

Advances in computational network modeling, and electronics have permitted development of a bizarre new class of truly biomimetic beasts. But it isn’t as easy as merely taking apart an animal or plant and copying what you see.

“Evolution doesn’t always come up with the best solution from an engineer’s perspective,” says Professor Macmillan.

Despite these evolutionary pitfalls, biomimetics has already produced swimming robots that achieve propulsion by whole body undulations or tail flapping and robots that walk using multiple jointed legs to mediate locomotion. Inroads are even being made in flying robots that fly by flapping mechanical wings.

Professor Macmillan has focused his research on the Yabby’s powerful tail, and it has revealed some interesting implications for future robotic design.

“The tail of the Yabby acts like a hinged lever, changing form to act as a sail for steering or a powerful paddle for swimming. The arrangement of muscles and nerves presents an interesting case study in biological solutions to problems associated with the dynamics and control of multi-jointed levers,” explains Professor Macmillan.

“Such levers could be useful in design of multi-jointed legs for mobility over difficult terrain, or in activities requiring precision lifting and leverage,” he says.

To find how the Yabby controls its tail, Professor Macmillan’s group recorded the activity from individual nerve cell sensors in the tail called Muscle Receptor Organs, while simultaneously recording the activity in the nerves and muscles that control each tail segment.

What they discovered was a feedback system for controlling complex movements that would delight any engineer. But there is a problem.

“We cannot figure out what the yabby uses this system for,” says Professor Macmillan.

“The system works perfectly when isolated in a dish. But when we examine the system in a freely behaving animal to try and find out what the Yabby uses it for in its natural environment, the system behaves contrary to what we or an engineer might expect. In fact, the sensors hardly fire at all during movements initiated by the animal itself.

“The implications of these experiments are particularly pertinent if the interpretations are to inform or lead robotic design.

“Evolution does not necessarily produce an engineer’s solution to an animal’s problem. It simply produces one that works, one that is selected because its features give the individual an edge – even a slight one – over its competitors in the game of survival.

“Biomimetic researchers also need to be aware that animals carry design features that reflect their evolutionary history as well as responses to their present situation. When we dissect them we may find features and solutions that appear inefficient or counter intuitive. The human appendix is one example of this.

“The space and defence industries are providing the biggest push for biomimetic research. NASA wants to expand its use of robots to carry out a multitude of tasks in space, but the cost of lifting the current generation of heavy robots into space is prohibitive.

“By studying invertebrates like the Yabby and its marine relatives, it may be possible to reverse engineer their neurological systems and build miniature, lightweight and autonomous robots capable of performing the range of complex tasks needed to explore Mars and beyond.”


Professor Macmillan’s research is published in the April 2001 Biological Bulletin.

Contact: Jason Major
University of Melbourne


[Image 1: (22KB)]
Testing the Yabby’s defences. A ball is passed in front of the yabby
and its response observed. Researchers record what nerves fire in the
yabby’s tail in response to such stimuli. This gives researchers a
better understanding of how the yabby’s nervous system works and for
what purposes. Photo copyright (c) 2002 University of Melbourne zoology

[Image 2: (12KB)]
The humble Australian yabby, Cherax destructor Photo copyright (c) 2002
University of Melbourne zoology