What divides gregarious gourmands from lone eaters? Ask the nematode worm

A microscopic worm that spends much of its short life foraging for food has shed light on how social eating in higher animals may have evolved.

Studies of the nematode worm by researchers at the Medical Research Council Laboratory of Molecular Biology in Cambridge have revealed why some like to dine alone while others eat in groups – a finding that could explain the evolution of similar behaviour in humans.

A single mutation in a gene responsible for a key protein of the worm's nerves can switch the animal's dining preference from social to solitary eater.

A similar gene is known to exist in humans and although it too is involved in controlling the feeding impulse, it is not known whether it has played a role in the evolution of social feeding. Dr Mario de Bono, the study leader, said: "What we're trying to do is to understand how a simple social behaviour is brought about. We're trying to look into the mind of an animal to see how a social behaviour occurs."

Research published today in the journal Nature shows that a neuropeptide receptor – a protein involved in the transmission of nerve impulses – called NPR-1 is responsible for determining whether a nematode is a social or solitary feeder.

Social feeders usually aggregate in groups at the edge of a "lawn" of bacteria, the nematodes preferred food. In contrast, solitary feeders actively avoid each other when dining.

Dr de Bono said that social feeding had probably evolved because it helped individuals to eat food that would otherwise be difficult for solitary individuals to consume. "Many bacteria can kill the worms by producing toxins. It may be that by eating in groups the worms can secrete enough enzymes to destroy these toxins," Dr de Bono said. Animals such as wolves demonstrated similar group behaviour, he said.