SAY “laboratory animal” and most people will think of mice. A few sophisticates might nominate the fruit fly. But rare will be the person who suggests the roundworm. Roundworms—or rather one species of them called C. elegans—are important animals to science. C. elegans have a fixed number of cells in their bodies, including exactly 302 nerve cells, and they were the first animals to have their genomes unravelled, which means they are among the best understood. They are, however, a mere millimetre long, which makes them hard to handle. If that handling could be automated, the ability to grow worms in bulk might revolutionise the study of many aspects of biology—not least, drug discovery.

Such automation is precisely what Mehmet Fatih Yanik of the Massachusetts Institute of Technology and his colleagues have in mind. They have created a miniature production line to streamline the process of testing drugs on worms. Their system is able to isolate a worm, perform precise laser surgery on it in order to sever just one of its neurons, treat it with a candidate chemical compound and, after a suitable incubation period, screen it to look for signs of drug-induced regeneration of the damaged cell.

To move and manipulate the worms the device, a plastic chip with an area of one square centimetre, uses a tiny plumbing system that consists of a network of capillaries etched into the chip. This sort of technology, known as microfluidics, has long been used to manipulate cells, proteins and biological fluids. Never before, though, has it been used to manipulate entire animals.

The worms are first sucked out of a holding chamber and into a channel. Here a single hole draws fluid out of the channel as it passes by. If there is a worm in the fluid it is drawn towards the hole and held in place by the suction.

When a captured worm is detected the suction on the hole is released. Simultaneously, however, a whole series of holes in the opposite wall of the channel pull the worm towards that wall, stretching the animal out as they do so. The roof of the channel then descends, immobilising the worm completely. The roof is made of a thin membrane that can be pushed down onto the creature.

That done, the chip, with its immobilised worm, is swung under a microscope armed with a laser which can produce pulses of infra-red light less than a billionth of a second long. The relevant nerve cell is selected by specially designed software and is cut by the laser. The worm is then funnelled into an incubation well and exposed to a dose of the potential drug. The whole process is over in about 20 seconds. Two or three days later, the procedure is repeated, except that the microscope examining the worm is looking for signs of nerve regeneration.

Using this technique Dr Yanik's team have been able to carry out a preliminary screening of 10,000 worms in a single month. Previously, a task like that would have taken years. A case, then, not so much of the worm turning as the worm's turn.