Figure 2

Stylet neurons are olfactory neurons.

(A) Orco antibody (red) was localized to the distal part of the labrum of the stylet, where apical and subapical sensilla (red-dotted box and arrows in a, b) were innervated by Orco-expressing neurons, while the campaniform sensilla were not innervated by Orco neurons (white-dotted circles and arrowheads in c,d). b and d: magnified images of red-dotted boxes in a,c. Diagrams represent neuronal organizations in the labrum of the stylet in the mosquito mouthpart (e). (B) Localization of AaOr8 gene in the labrum using in situ hybridization. AaOr8-expressing neurons were localized (white arrowheads) in labrum and were co-localized with AaOrco (green). DNA staining with DAPI (blue) demonstrated that neurons were identified in the labrum of the mosquito stylet. (C) A cluster of AaOr49 neurons was also identified in labrum (red), which were co-localized with AaOrco (green). (D) Neurons in the stylet of the mosquito sent their axons to two discrete glomeruli (arrowheads in a, b) of the antennal lobes (ALs) in the brain (white-dotted circles in a). Neuronal tracts from suboesophageal ganglion (SOG) to ALs were also observed (arrows in a). Projections from stylet to SOG were also observed (dotted box and red arrow in a). Pairs of MD2 (ST1) and MD3 (ST2) glomeruli (yellow and green dotted circles and arrows in b) in the ALs, targets of stylet olfactory receptor neurons (ORNs), were located in the ventro-medial part of the ALs by 3D reconstruction (MD2: yellow circles inside ALs; MD3: green circles inside ALs in c). Direction indicators in d represents as follows: a, anterior; p, posterior; v, ventral; d, dorsal. OL represents optic lobe.