Olfactory Sensory Neurons of the Asian Longhorned Beetle, Anoplophora glabripennis, Specifically Responsive to its two Aggregation-Sex Pheromone Components

Abstract

We performed single-sensillum recordings from male and female antennae of the Asian longhorned beetle, Anoplophora glabripennis, that included as stimuli the two components of this species' aggregation-sex pheromone in addition to various general odorants. We compared the aggregation-sex-pheromone-component responses of olfactory sensory neurons (OSNs) to those of OSNs that responded to a variety of plant-related odorants. In the smooth-tipped, tapered, trichoid sensilla on the most distal antennal flagellomeres nos. 10 or 11 of both males and females, we found OSNs with high-amplitude action potentials that were tuned to the aldehyde and alcohol pheromone components and that did not respond to various plant-related volatiles. Because this OSN type responded to both the alcohol and aldehyde components it cannot be considered to be specifically tuned to either component. These large-spiking OSNs were co-compartmentalized in these sensilla with a second, smaller-spiking OSN responding to plant-related volatiles such as geraniol, citronellal, limonene, 1-octanol, nerol and citral. The large-spiking OSNs thus appear to be a type that will be involved in aggregation-sex pheromone pathways targeting a specific glomerulus in the antennal lobe and in generating pheromone-related behavioral responses in A. glabripennis. In other sensilla located in these distal antennal flagellomeres as well as those located more proximally, i.e., mid-length along the antenna on flagellomere nos. 4-7, we found OSNs in blunt-tipped basiconic sensilla that were responsive to other plant-related volatiles, especially the terpenoids, (E,E)-alpha farnesene, (E)-β-farnesene, β-caryophyllene, and eugenol. Some of these terpenoids have been implicated in improving attraction to pheromone-baited traps. Some of these same OSNs responded additionally to either of the two sex pheromone components, but because these OSNs also responded to some of the above plant volatiles as shown by cross-adaptation experiments, these OSNs will not be the types that convey sex-pheromone-specific information to the antennal lobe.

The attractive host volatiles can enhance oviposition of Anoplophora glabripennis on a non‐host tree

“…Sensitivity of the ALB ovipositor should be studied in the future; it is likely that the chemical sensillum on the ovipositor will be different to those on the antennae, maxillary palps and labial palps. 37,38 Note: Data are mean ± standard error of four replicates. The percentage of effective oviposition pits = (the number of eggs and larvae per tree stems)/ (the number of oviposition pits per tree stems) × 100.…”

“…It seemed that the ovipositor of females could sense non‐host compounds to some extent, resulting in females abandoning the oviposition pit. Sensitivity of the ALB ovipositor should be studied in the future; it is likely that the chemical sensillum on the ovipositor will be different to those on the antennae, maxillary palps and labial palps 37,38 …”

Morphological and Ultrastructural Characterization of Antennal Sensilla and the Detection of Floral Scent Volatiles in Eupeodes corollae (Diptera: Syrphidae)

“…For example, in model insect D. melanogaster , sensilla basiconica usually houses two to four neurons, in which ab1D responded with a high degree of specificity to methyl salicylate ( de Bruyne et al, 2001 ). In Anoplophora glabripennis (Coleoptera: Cerambycidae), ORNs in blunt-tipped sensilla basiconica were responsive to eugenol and some terpenoids ( Wei et al, 2018 ). Moreover, the action potentials of ORNs lead to the activation of the second-order neurons in the brain to produce behavioral changes ( Wei et al, 2018 ).…”

“…In Anoplophora glabripennis (Coleoptera: Cerambycidae), ORNs in blunt-tipped sensilla basiconica were responsive to eugenol and some terpenoids ( Wei et al, 2018 ). Moreover, the action potentials of ORNs lead to the activation of the second-order neurons in the brain to produce behavioral changes ( Wei et al, 2018 ). A recent study showed that an odorant receptor EcorOR25 was narrowly tuned to aromatic compounds, particularly eugenol and methyl eugenol, which can strongly attract E. corollae adults of both sexes ( Li et al, 2020 ).…”

Genome-Wide Identification of the Odorant Receptor Gene Family and Revealing Key Genes Involved in Sexual Communication in Anoplophora glabripennis

“…Olfactory sensory neurons located in the trichomes of the amphoteric antennal whipstock, for example, are more sensitive to the male-produced aggregation-sex pheromones 4-(n-heptyloxy)butan-1-ol and 4-(n-heptyloxy)butanal. Olfactory neurons of the conical sensilla of whipstock, on the other hand, have more obvious responses to alcohols, aldehydes, and terpenes, indicating that different types of A. glabripennis sensilla may have selective sensitivity to odor cues [ 48 ]. In a previous study, Hu et al (2017) screened thirty-seven AglaORs on the A. glabripennis antennal transcriptome [ 49 ].…”