WASHINGTON, Nov. 7 (Xinhua) -- Researchers in the University of Iowa have discovered the first two genes involved in moisture sensing (hygrosensation).

The discovery also reveals a "two-sensor" hygrosensing system in fruit flies that may allow the flies to detect subtle changes in humidity -- an ability that is critical for the flies' survival.

The results appear in the Nov. 8 issue of journal Nature.

Subtle variations in humidity influence reproductive behavior and geographic distribution in many animals, including insects, reptiles and birds. Because of their small size, insects, in particular, require a finely tuned ability to detect moisture levels in their environment in order to survive. However, the mechanisms and molecules involved in moisture sensing have remained a mystery.

The researchers used various genetic techniques to study over 20 genes assumed to be involved in touch in fruit flies. Screeningeach gene mutation for its effect on the flies' ability to detect moisture, the researchers identified two genes that are required for normal moisture sensing.

Furthermore, they found that one of the genes, "nanchung," is involved in detecting dry air, while the other gene, "water witch," is required for detecting moist air.

The researchers also examined where the two genes are expressed in the fruit flies and determined that not only are two separate genes involved in hygrosensation, but also two types of neurons.

The researchers speculate that this two-sensor system may allow the flies to detect relative humidity with great sensitivity. "Two-sensor" system might also be a model for other sensory processes where the ability to detect subtle environmental changes is important, such as temperature sensing.