part of continuous with capable of Johnston organ VFB:FBbt_00004178 Yorozu et al., 2009, identify tonically activated Johnston's organ neurons that respond to forward or reverse deflection of the antenna. Genetic ablation of these neurons inhibits wind-induced behavioral responses without impairing hearing. Further, by expression of tetanus toxin, Kamikouchi et al., 2009, identify the same neuronal population as essential for gravitaxis behavior. Compound chordotonal organ of antennal segment 2 involved in hearing (Gopfert and Robert, 2002), direction-sensitive wind detection (Yorozu et al., 2009) and gravitaxis (Kamikouchi et al., 2009). The actin-filament rich basal tips of the Johnston's organ scolopidia connect to the inner surface of antennal segment 2, and the apical tips connect to the hook of antennal segment 3 (Gopfert and Robert, 2002). Its sensory neurons (Johnston's organ neurons or JONs) are connected to the Johnston's organ nerve (Kamikouchi et al., 2006), and predominantly innervate the antennal mechanosensory and motor center (AMMC). There are 477 +/- 24 cell bodies, arranged in a bowl shape lying vertically with the 'top' facing the lateral side, and forming a ring around the antennal nerve (Kamikouchi et al., 2006). JONs connecting to opposing sides of the hook are alternatively stimulated by stretching or compression according to the hook's oscillatory movement (Gopfert and Robert, 2002). JO chordotonal organ of antennal segment 2 FBbt:00004178 Johnston's organ fly_anatomy.ontology antennal segment 2 sense organ internal compound sense organ auditory sense organ adult chordotonal organ Johnston organ bundle of antennal nerve detection of mechanical stimulus involved in equilibrioception detection of mechanical stimulus sensory perception of wind