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Wednesday, 27 September, 2000, 18:13 GMT 19:13 UK
When slime is not so thick
Slime Bio-Mimetic Control Research Center
Slime before (left) and after (right) negotiating the maze
Scientists have discovered that a single-celled organism can negotiate the shortest way through a maze.

It means that some of the lowliest creatures in the plant and animal kingdoms, such as slime and amoeba, may not be as primitive as once thought.

Pieces of slime mould, an amoeba-like organism, were enticed through a 30-square-centimetre (five-square-inch) maze by the prospect of food at the end of the puzzle.

The researchers believe the slime is exhibiting some form of primitive intelligence.

Toshiyuki Nakagaki of the Bio-Mimetic Control Research Centre, Nagoya, Japan, placed pieces of the slime mould Physarum polycephalum in an agar gel maze comprising four possible routes.

Normally, the slime spreads out its network of tube-like 'legs', called pseudopodia, to fill all the available space.

But when two pieces of food were placed at separate exit points in the labyrinth, the organism squeezed its entire body between the two nutrients.

It adopted the shortest possible route, effectively solving the puzzle.

'Cellular computation'

Announcing their findings in the journal Nature, the researchers say they believe the organism changed its shape to maximise its foraging efficiency and therefore its chances of survival.

The meal of ground oat flakes led to a local increase in contraction of the organism's tube-like structures, propelling it towards the food.

"This remarkable process of cellular computation implies that cellular materials can show a primitive intelligence," the team writes in Nature.

Slime mould is one of a group of single- to multi-celled organisms traditionally classified as fungi but having characteristics of both plants and animals.

They reproduce by spores, but their cells can move like an amoeba and they feed by taking in particles of food.

Some types of slime mould are the bane of gardeners, forming a jelly-like surface on grass.

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