Caenorhabditis elegans exhibit either social or solitary feeding on bacterial lawns, but the neural mechanisms that control this behavior have been unclear. Two papers in October 31 Nature, show that nematode social feeding is controlled by neurons that respond to stress and aversive environmental conditions.

Mario de Bono at the University of California at San Francisco, USA, and colleagues studied a mutant C. elegans strain and observed that ablation of the nociceptive neurons ASH and ADL transforms social animals into solitary feeders. They suggest a model for regulation of social feeding by opposing sensory inputs. "Aversive inputs to nociceptive neurons promote social feeding, whereas antagonistic inputs from neurons that express osm-3 inhibit aggregation," write the authors (Nature, 419: 899-903, October 31, 2002).

In the second paper Juliet Coates at the MRC Laboratory of Molecular Biology, Cambridge, UK, with de Bono, showed that antagonistic signaling pathways...