Fig. 1.

Organization of the adult Drosophila gustatory system. There are three types of taste sensilla in the different taste organs: taste bristles (blue dots), taste pegs (green dots), and pharyngeal hairless sensilla (magenta dots). The taste bristles are distributed in the anterior wing margins (blue in a), the distal segment of the legs (brown in b), and the labellum (black, blue and red in c). The taste pegs are located between pseudotrachea in the labellum (green in d). The hairless sensilla are located in the three internal pharyngeal taste organs: labral sense organs (LSO), ventral and dorsal cibarial sense organs (VCSO and DCSO) (magenta in e). f–h Schematic diagrams showing the structures of three types of taste sensilla. All of them have a terminal pore (arrows) that allows tastants to make contact with the taste neurons in each sensillum. The taste bristle has 2–4 gustatory receptor neurons (GRNs) (4 GRNs in this schematic example) whose dendrites extend up to the tip of the taste sensillum (f). The taste peg has one GRN (g). Both taste bristles and taste pegs have one mechanosensory neuron (MN) at the base of each sensillum (black in f, g). The pharyngeal hairless sensilla usually do not have mechanosensory neurons, except for the #8 and #9 LSO sensilla. The number of GRNs in the pharyngeal hairless sensilla can vary from 1 to 8 (8 GRNs in this schematic example) (h)