Fig. 1.

Assessment of fungal invasion of the brain. Confocal images demonstrating the restriction of fungal invasion into the brain. Host brain is identified by immunofluorescence of neuronal synapses (green, anti-SYNORF1), while fungal cells and host tracheae are stained with calcofluor white (red, antichitin). All images are represented as maximum projections of z-stacks. (A) Portion of the mushroom body (green) in the brain of an uninfected (control) ant, 156× magnification. (Scale bar, 10 µm.) (B) Portion of the optic lobe (green) in the brain of an infected, behaviorally manipulated ant, 60× magnification. (Scale bar, 20 µm.) Arrows denote fungal hyphal bodies (red), identified by their short, rod-like structure and the presence of septa. Arrowheads denote tracheae (red), located within the brain (green), and identified by their long, filamentous structure and lack of septa. Note the restriction of fungal cell bodies to outside of the brain. (C) Zoom-in (96× magnification) of region of interest noted in B. (Scale bar, 20 µm.) While the presence of tracheae inside the brain is evident (arrowheads), there is no detection of fungal hyphal bodies (arrows) inside the brain.