Recent advances in insect olfaction, specifically regarding the morphologyand sensory physiology of antennal sensilla of the female sphinx moth Manduca sexta

The antennal flagellum of female Manduca sexta bears eight sensillum types: two trichoid, two basiconic, one auriculate, two coeloconic, and one styli form complex sensilla. The first type of trichoid sensillum averages 34 mum in length and is innervated by two sensory cells. The second type averages 26 mum in length and is innervated by either one or three sensory cells. T he first type of basiconic sensillum averages 22 mum in length, while the s econd type averages 15 mum in length. Both types are innervated by three bi polar sensory cells. The auriculate sensillum averages 4 mum in length and is innervated by two bipolar sensory cells. The coeloconic type-A and type- B both average 2 mum in length. The former type is innervated by five bipol ar sensory cells, while the latter type, by three bipolar sensory cells. Th e styliform complex sensillum occurs singly on each annulus and averages 38 -40 mum in length. It is formed by several contiguous sensilla. Each unit i s innervated by three bipolar sensory cells. A total of 2,216 sensilla were found on a single annulus (annulus 21) of the flagellum. Electrophysiologi cal responses from type-A trichoid sensilla to a large panel of volatile od orants revealed three different subsets of olfactory receptor cells (ORCs). Two subsets responded strongly to only a narrow range of odorants, while t he third responded strongly to a broad range of odorants. Anterograde label ing of ORCs from type-A trichoid sensilla revealed that their axons project ed mainly to two large female glomeruli of the antennal lobe. (C) 2001 Wile y-Liss, Inc.