Study In Roundworms Provides Evidence For Darwin's Hypothesis

Researchers have produced some of the first evidence for the famed naturalist Charles Darwin's hypothesis that domestication and natural selection -- the process by which organisms better adapted to their surroundings survive and create more offspring -- work in the same ways. The research, conducted by an international team, including those from Northwestern University in the US, found that natural selection acts on the same genes that control the sense of smell in wild roundworms as also found previously in domesticated worms in the lab.

The study, published in the journal Nature Ecology and Evolution, was carried out using a combination of laboratory experiments, computational genomic analysis, and field work.

The researchers showed that natural selection acted on signal-sensing receptors rather than parts further down the genetic process.

The study was performed on the model organism C.elegans -- a one-millimetre-long roundworm typically found in gardens and compost piles, feeding particularly on rotten fruits and bacteria.

The researchers said that the roundworm relies so much on its sense of smell to assess food levels and competition that getting its olfaction right could mean the difference between its life and death.

If they smell enough food in their environment, the researchers said, they will stay, grow, and reproduce.

However, if they sensed food shortage or too much competition from other worms, they may go on a risk prone journey to find a less populated place with more food.

This process, the researchers called "dauer", delayed growth and reproduction in the worms.

Dauer, the study noted, decreased the chances of the worms reproducing in the short term, in order for them to survive in the long run.

 "At some point in their lives, these worms must make a gamble," said Erik Andersen, lead author of the study from Northwestern University.

Andersen added that the worms staying behind already begin multiplying by the time it takes the risk-taking explorers to come out of dauer and start growing again.

"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," Andersen said.

The researchers found that evolution plays a significant role in a worm's decision to either stay or enter dauer.

The number of genetic receptors in the roundworms to process smell played a key role in the decision making process, the study noted.

The roundworms with two receptors, the researchers said, had a heightened sense of smell which allowed them to assess their environment for resources in a much better way, helping them make a better gamble.

"If worms can smell large numbers of worms around them, that gives them an advantage," Andersen said.

While the same discovery was made earlier in worms domesticated in the lab, the current study showed that the same process happened in natural populations, the researchers said.

 "We can see specific evidence in these two genes that artificial and natural selection act similarly," Andersen said.