Maxillary palps are broad spectrum odorant detectors in culex quinquefasciatus

Zainulabeuddin Syed, Walter S. Leal

Research output: Contribution to journalArticlepeer-review

87 Scopus citations


A single type of olfactory sensilla on maxillary palps in many species of mosquitoes houses a very sensitive olfactory receptor neuron (ORN) for carbon dioxide reception. We performed extensive single sensillum recordings from this peg sensillum in Culex quinquefasciatus and have characterized the response threshold and kinetics for CO2 reception, with a detection threshold less than the CO2 concentration in the atmosphere. This ORN responded in a tonic mode to lower concentrations of CO2, whereas higher concentrations generated a phasic-tonic mode of action potential firing. Sensillum potentials accurately represented the response magnitude and kinetics of carbon dioxide - elicited excitatory responses. Stimulation of these ORNs with human breath, a complex mixture of mosquito kairomones and up to 4.5% CO2, elicited excitatory responses that were reliably detected by CO2-sensitive ORNs. Another ORN housed in these sensilla responded to 1-octen-3-ol and to various plant-derived compounds, particularly floral and green leaf volatiles. This ORN showed remarkable sensitivity to the natural enantiomer, (R)-(-)-1-octen-3-ol, rivaling pheromone-detecting ORNs in moths. Maximum neuronal response was elicited with a 10 ng dose. A biological, ecological role of maxillary palps in detection of plant- and nectar-related sources is proposed.

Original languageEnglish
Pages (from-to)727-738
Number of pages12
JournalChemical Senses
Issue number8
StatePublished - Oct 2007

Bibliographical note

Funding Information:
This work was supported in part by National Institutes of Health grant (1U01AI05826-01) and a research agreement between Bedoukian Research Inc. and University of California (UC), Davis. We thank Bedoukian Research Inc. for providing optically pure compounds and Dr Anthony Cornel and Julie Christensen of UC Davis for providing mosquitoes.


  • CO detection
  • Mosquito olfaction
  • Phasic-tonic responses
  • Plant/nectar location
  • Single sensillum recordings

ASJC Scopus subject areas

  • Physiology
  • Sensory Systems
  • Physiology (medical)
  • Behavioral Neuroscience


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