SENSORY PROJECTIONS OF IDENTIFIED COXAL HAIR SENSILLA OF THE SCORPIONHETEROMETRUS-FULVIPES (SCORPIONIDAE)

The topography of long hair sensilla on the coxae of walking legs and pedipalps of the scorpion Heterometrus fulvipes is described. Identifi ed long hair sensilla are cobalt filled, and central projections of se nsory fibres are reported for the first time in the suboesophageal gan glion of this scorpion. The afferent fibres arising from each long hai r sensilla segregate into ventral, dorsomedial and dorsal tracts upon their entry into the suboesophageal ganglion. These transverse tracts bifurcate towards the middle of the leg neuromere and form three ipsil ateral, plurisegmental, longitudinal sensory pathways. Filling a pair of bilaterally distributed long hair sensilla shows bilaterally arrang ed longitudinal afferent tracts interconnected by distinct transverse commissures. Similar patterns of sensory projections are observed when filling homologous hairs on other legs and pedipalps. Numerous fine c ollaterals arise from the longitudinal sensory trancts that subdivide and end in small blebs presumed to be presynaptic endings. The dorsal and dorsomedial longitudinal tracts and their respective commissures a re in close association with the dendritic arborisations of pedipalpal and leg motor neurons, suggesting direct contact between them. The pr obable functions of these multisegmental hair afferent pathways are di scussed.