Sex-specific non-pheromonal taste receptors in Drosophila

Taste receptors have recently been reported in Drosophila [1,2], but little is known of the relation between receptor and response. Morphological stud ies of the distribution of chemosensory sensilla indicate that the fruit fl y has two major sites of gustation: the proboscis and the legs [3], The tas te sensilla on both these sites are similar in structure and each sensillum generally houses four gustatory neurons [4]. Early anatomical observations have demonstrated a sexual dimorphism in the number of tarsal sensilla [5] and in their central projections [6], We measured the electrophysiological responses of the prothoracic taste sensilla to non-pheromonal substances - salts, sugars and water - and found a clear sexual dimorphism, From the re sponse profile of individual sensilla, we were able to distinguish three ty pes of tarsal sensilla in females as against only two types in males. The f emale specific type, which responded specifically to sugar, was absent in m ales except when male gustatory neurons were genetically feminised, The fac t that tarsal gustatory hairs exhibit a sexual dimorphism that affects the perception of non-pheromonal compounds suggests that sexual identity is mor e complex than has previously been thought [7,8].