Characterization of olfactory receptor neurons for pheromone candidate and plant volatile compounds in the clover root weevil, Sitona lepidus

• Published in: Journal of insect physiology Vol. 59; no. 12; pp. 1222 - 1234
• Main Authors: Park, Kye Chung, McNeill, Mark, Unelius, C. Rikard, Oh, Hyun-Woo, Suckling, David M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2013
• Subjects: Animals; Clover root weevil; Ecological chemistry; Ekologisk kemi; Female; females; Host-plant volatile; leaves; Male; males; neurons; Olfactory receptor neuron; Olfactory Receptor Neurons - physiology; Olfactory sensilla; Pheromone; Pheromones - physiology; sensilla; Single-sensillum recording; Sitona lepidus; stereoisomers; Trifolium - chemistry; volatile compounds; Volatile Organic Compounds; Weevils - physiology; Pheromone; Host-plant volatile; Single-sensillum recording; Olfactory sensilla; Olfactory receptor neuron; Clover root weevil
• ISSN: 0022-1910; 1879-1611; 1879-1611
• DOI: 10.1016/j.jinsphys.2013.10.002

•The clover root weevil, Sitona lepidus, antennal structure and olfactory systems investigated.•S. lepidus antennae contain ORNs responsive to either pheromone or plant-volatile compounds.•Most ORNs identified were highly specialized for a narrow range of compounds.•Sexual dimorphism was observed in the response to pheromone compounds.•Paired-ORNs may play a critical role in species-recognition and host-location in Sitona weevils. Antennal olfactory receptor neurons (ORNs) for pheromone and plant volatile compounds were identified and characterized in male and female clover root weevil, Sitona lepidus (Gyllenhal), using the single sensillum recording technique with five pheromone-related compounds, and 40 host and non-host plant volatile compounds. Overall, seven different types of olfactory sensilla containing specialized ORNs were identified in each sex of S. lepidus. Among them, three different types of sensilla in the males and two types in the females housed ORNs specialized for pheromone-related compounds. The ORNs in males were specialized for 4-methyl-3,5-heptanedione or one or more of four stereoisomers of 5-hydroxy-4-methyl-3-heptanone. In contrast, female sensilla did not contain ORNs sensitive to 4-methyl-3,5-heptanedione while they contained ORNs sensitive to and specialized for the stereoisomers of (4S,5S)-5-hydroxy-4-methyl-3-heptanone. In addition to the pheromone-related ORNs, four types of olfactory sensilla contained ORNs responsive to plant volatile compounds in male S. lepidus, and five types in females. Most of the ORNs identified in S. lepidus showed a high degree of specificity to specific volatile compounds although some of the active compounds showed overlapping response spectra in the ORNs across different types of sensilla. The most active plant volatile compounds were the four green leaf volatile compounds, (E)-2-hexenol, (Z)-2-hexenol, (Z)-3-hexenol and (E)-2-hexenal, and isomers of two monoterpenols, (±)-linalool and (±)-α-terpineol, all eliciting strong responses from relatively large numbers of ORNs in male and female S. lepidus. Our study indicates that S. lepidus has a set of highly sensitive and selective ORNs for pheromone and plant volatile compounds. Further work is needed to elucidate the behavioral implications of these findings.