The long and short of worm development.

"How do you take a round ball of cells and turn it into a long, thin worm?" wonders Judith Austin of the University of Chicago. That's what Caenorhabditis elegans does midway through its development. Within an hour or two, the worm more than triples its length, without adding any new cells.

To answer Austin's question, imagine squeezing a ball of pizza dough into a thinner shape. The same phenomenon explains the rapid elongation of C elegans, says Austin.

She and her colleagues hit upon this answer when they found a mutant strain of the worm that turns out much shorter than normal. They tracked down the mutant gene responsible and determined that it produces a protein unable to help reorder the meshwork of fibers that forms a skeleton within worm cells.

In normal worms, the protein, dubbed SMA-1 for small-1, aids in rearranging these fibers into long, parallel bundles. Since these fibers connect to the cell surface, the process changes the shape of individual cells from spherical to elongated. Presto, one long worm.