Science: Study Shows How Animals "Smell" Each Other's Alarm Signals

The mammalian nose contains a specialized sensor that detects chemical alarm signals emitted by fellow animals, Swiss researchers report in a new study published in Science.

The so-called "Grueneberg ganglion" is a tight ball of round cells located near the tip of the nose. It was discovered in 1973, but its function has been a matter of controversy ever since.

In a study appearing in the journal's 22 August issue, Julien Brechbühl and colleagues at the University of Lausanne show that the Grueneberg ganglion picks up alarm pheromones produced by other members of the same species when they're in distress.

Organisms including plants, fish, insects and mammals are known to emit these pheromones, but it's been unclear exactly what the compounds are, how they're produced and how they're detected.

Alarm pheromones are extremely volatile and can be captured by collecting the air around the stressed animal. After being added to a buffer solution, the pheromones will evaporate quickly when the liquid is left in an open container.

The researchers compared how normal mice and mice lacking a Grueneberg ganglion responded to alarm pheromones evaporating out of a bowl in the corner of the animals' cage.

Whereas normal mice stopped exploring their cage and froze in a corner, the other mice kept wandering around, seemingly unaware of the danger signals.

Both groups were able to sniff out an Oreo cookie hidden in the bedding of their cage, however, indicating that their olfactory system was otherwise working normally.

The authors also used electron microscopy to study the ganglion's physical appearance, and they determined that these neurons have features similar to those of other olfactory neurons.

Kathy Wren

21 August 2008