CHICAGO, Sept. 26 -- In a study posted on the website of Northwestern University (NU) on Thursday, researchers found that natural selection acts on the same genes that control wild roundworms' sense of smell as were previously found in domesticated worms in the lab.

The researchers used a combination of laboratory experiments, computational genomic analysis and field work.

A keystone model organism, C. elegans is a one-millimeter-long roundworm that lives in decaying organic matter, particularly rotten fruits, and feeds on bacteria. These roundworms are typically found in gardens and compost piles.

For C. elegans, having a keen sense of smell can be the difference between life or death. If they smell enough food in their environment, they will stay, grow and reproduce. If they sense a shortage of food and/or too much competition from other worms, they will undertake a long and potentially fatal journey in search of a more favorable environment. This process, called "dauer," delays growth and reproduction.

"At some point in their lives, these worms must make a gamble," said NU's Erik Andersen, who led the study. "In the time it takes for a worm to come out of dauer and start growing again, the worm that stayed behind has already been multiplying. If the food runs out, then the dauer worm made the right decision and wins. If the food doesn't run out, then the dauer worm loses."

The researchers found that evolution plays a significant role in a worm's decision to stay or enter dauer. Some roundworms have one genetic receptor to process scents; other roundworms have two. The roundworms with two receptors have a heightened sense of smell, which allows them to better assess the availability of resources in their environment and make a better gamble.

"If worms can smell large numbers of worms around them, that gives them an advantage," Andersen said. "This was discovered in a previous study of artificial selection in worms. Now we also found that result in natural populations. We can see specific evidence in these two genes that artificial and natural selection act similarly."

The study was published this week in the journal Nature Ecology & Evolution.