The desat1 gene possesses an extraordinary-maybe unique-feature in the control of sensory communication systems: it codes for the two principal and complementary aspects-the emission and the reception-of Drosophila sex pheromones. These two complex aspects depend on separate genetic control indicating that desat1 pleiotropically acts on pheromonal communication. This gene also control other characters either related to reproduction and to osmoregulation. Such a functional pleiotropy may be related to the molecular structure of desat1 gene which combines a highly conserved coding region with fast evolving regulatory regions: It produces at least five transcripts all giving rise to the ∆9-desaturase enzyme.