Protapion trifolii and P. fulvipes (Coleoptera: Brentidae) are major pests in European clover seed production. Previous studies have reported a high host plant fidelity of these weevils for red and white clover species, respectively, driven by host plant olfactory cues. Given the specific host preferences observed in these weevils, we aimed to elucidate to which extent such selectivity is reflected in their peripheral olfactory systems. Using an electrophysiological approach, we performed the first functional characterisation of olfactory sensory neurons (OSNs) in P. trifolii to a panel of volatile compounds emitted by red clover plants, and compared the results with the reported OSN types of P. fulvipes. Nineteen OSN classes were characterized in P. trifolii, with the majority of these neurons responding strongly to common volatiles released by the host plant. Based on response profiles, eight of these OSN classes have clear matches to OSN classes in P. fulvipes. The OSN colocalisation patterns and antennal frequency of these classes are similar in the two species. Additionally, the responses of these OSNs are generally highly conserved in the two species, with clear response shifts only revealed for two of the OSN classes. These response shifts in combination with additional response dissimilarities for compounds that vary in abundance between red and white clover plants may underlie the species-specific host preferences. Further behavioural and field experiments should focus on these differentially detected compounds to elucidate their potential role in host selection and use in semiochemical-based control of these pests.

中文翻译：

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红三叶草种子象鼻虫，Protapion trifolii（鞘翅目：Brentidae）中嗅觉感觉神经元的特征，并与近缘种P.fulvipes进行比较。

在欧洲三叶草种子生产中，三叶草和小叶黄腐菌（鞘翅目：Brentidae）是主要害虫。先前的研究已报道，在宿主植物嗅觉提示的驱动下，这些象鼻虫对红色和白色三叶草物种的保真度很高。给定在这些象鼻虫中观察到的特定宿主偏好，我们旨在阐明这种选择性在其外周嗅觉系统中反映的程度。使用电生理方法，我们对三叶草中的嗅觉感觉神经元（OSN）进行了第一个功能表征，将其与一组由红三叶草植物释放的挥发性化合物进行了比较，并将结果与​​报道的OSN型小叶黄腐病进行了比较。P. trifolii中有19个OSN类，这些神经元中的大多数对宿主植物释放的常见挥发物有强烈反应。根据响应配置文件，这些OSN类中的八个与P.fulvipes中的OSN类具有明确的匹配。这两个类别的OSN共定位模式和天线频率相似。此外，这些OSN的响应通常在两个物种中高度保守，只有两个OSN类才显示出明显的响应变化。这些响应变化与红三叶草植物之间的丰度变化的化合物的其他响应差异相结合，可能是特定物种宿主偏好的基础。