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Fine structure and primary sensory projections of sensilla located in the labial-palp pit organ of Helicoverpa armigera (Insecta)


The fine structure and primary sensory projections of sensilla located in the labial-palp pit organ of the cotton bollworm Helicoverpa armigera (Insecta, Lepidoptera) are investigated by scanning electron and transmission electron microscopy combined with confocal laser scanning microscopy. The pit organ located on the third segment of the labial palp is about 300 μm deep with a 60-μm-wide opening, each structure containing about 1200 sensilla. Two sensillum types have been found, namely hair-shaped and club-shaped sensilla, located on the upper and lower half of the pit, respectively. Most sensilla possess a single dendrite. The dendrite housed by the club-shaped sensilla is often split into several branches or becomes lamellated in the outer segment. As reported previously, the sensory axons of the sensilla in the labial pit organ form a bundle entering the ipsilateral side of the subesophageal ganglion via the labial palp nerve and project to three distinct areas: the labial pit organ glomerulus in each antennal lobe, the subesophageal ganglion and the ventral nerve cord. In the antennal lobe, the labial pit organ glomerulus is innervated by sensory axons from the labial pit organ only; no antennal afferents target this unit. One neuron has been found extending fine processes into the subesophageal ganglion and innervating the labial palp via one branch passing at the base of the labial palp nerve. The soma of this assumed motor neuron is located in the ipsilateral cell body layer of the subesophageal ganglion. Our results provide valuable knowledge concerning the neural circuit encoding information about carbon dioxide and should stimulate further investigations directed at controlling pest species such as H. armigera.

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Correspondence to Feng-Ming Yan or Gui-Rong Wang.

Additional information

This work was supported by the following granting bodies: National Science Foundation of China (grant no. 31230062 to G.R.W.), Special Fund for Agro-scientific Researches of the Public Interests (grant no. 201203036 to F.M.Y.) and Opening Project of State Key Laboratory for Biology of Plant Disease and Insect Pests (grant no. SKL20120P09 to X.C.Z.).

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Zhao, X., Tang, Q., Berg, B.G. et al. Fine structure and primary sensory projections of sensilla located in the labial-palp pit organ of Helicoverpa armigera (Insecta). Cell Tissue Res 353, 399–408 (2013).

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  • Labial-palp pit organ
  • CO2-sensing sensillum types
  • Sensory projections
  • Antennal lobe
  • Helicoverpa armigera (Insecta)