Integrated Ultrastructural and Transcriptomic Analysis of the Proboscis in Apis cerana cerana Under Different Foraging Conditions

Abstract

Simple Summary The proboscis of the eastern honey bee, Apis cerana cerana, is traditionally considered a feeding organ used for nectar collection. However, its potential structural and molecular characteristics associated with chemical sensing during foraging remain insufficiently understood. In this study, we combined scanning electron microscopy and transcriptome sequencing to investigate the structural and molecular characteristics of the proboscis under different foraging conditions. Ultrastructural observations revealed abundant hair-like sensilla and specialized ridge–groove structures on the glossa and flabellum, suggesting possible specialization of the proboscis surface for interactions with external stimuli. Transcriptome analyses showed substantial differences in gene expression between pollen-load groups and bees without visible pollen loads, while differences between the two pollen sources were relatively limited under the present experimental conditions. Several candidate OR-like transcripts, including odorant receptor-like genes, were identified in the proboscis transcriptome, and phylogenetic analyses revealed conserved and lineage-specific evolutionary patterns among candidate sequences. These findings provide preliminary evidence that the honey bee proboscis contains structural and molecular features potentially associated with chemosensory processes, although further functional studies are required. This study provides new insights into the potential involvement of the honey bee proboscis in sensory-related processes during foraging behavior.